diff options
Diffstat (limited to 'src/3rdparty/libpng/libpng.3')
| -rw-r--r-- | src/3rdparty/libpng/libpng.3 | 1649 |
1 files changed, 1332 insertions, 317 deletions
diff --git a/src/3rdparty/libpng/libpng.3 b/src/3rdparty/libpng/libpng.3 index 6b77fde4e7..ecc42777bf 100644 --- a/src/3rdparty/libpng/libpng.3 +++ b/src/3rdparty/libpng/libpng.3 @@ -1,6 +1,6 @@ -.TH LIBPNG 3 "January 3, 2010" +.TH LIBPNG 3 "February 3, 2011" .SH NAME -libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 +libpng \- Portable Network Graphics (PNG) Reference Library 1.5.1 .SH SYNOPSIS \fI\fB @@ -16,6 +16,14 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_build_grayscale_palette (int \fP\fIbit_depth\fP\fB, png_colorp \fIpalette\fP\fB);\fP + +\fI\fB + +\fBpng_voidp png_calloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP + +\fI\fB + \fBvoid png_chunk_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP \fI\fB @@ -48,7 +56,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_structp png_create_read_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP +\fBpng_structp png_create_read_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP \fI\fB @@ -56,7 +64,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_structp png_create_write_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP +\fBpng_structp png_create_write_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP + +\fI\fB + +\fBvoid png_data_freer (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIfreer\fP\fB, png_uint_32 \fImask)\fP\fB);\fP \fI\fB @@ -72,6 +84,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_err (png_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + \fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP \fI\fB @@ -84,7 +100,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_free_default(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP +\fBvoid png_free_default (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP \fI\fB @@ -92,75 +108,89 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_byte png_get_bit_depth (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_byte png_get_bit_depth (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP +\fBpng_uint_32 png_get_bKGD (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP \fI\fB -\fBpng_byte png_get_channels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_byte png_get_channels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP +\fBpng_uint_32 png_get_cHRM (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP +\fBpng_uint_32 png_get_cHRM_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_chunk_cache_max (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_color_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fI\fB + +\fBpng_alloc_size_t png_get_chunk_malloc_max (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_color_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_compression_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_compression_buffer_size (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_copyright (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_compression_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_error_ptr (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_copyright (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_filter_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_current_row_number \fI(png_const_structp\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP +\fBpng_byte png_get_current_pass_number \fI(png_const_structp\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP +\fBpng_voidp png_get_error_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_header_ver (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_filter_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_header_version (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_gAMA (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP +\fBpng_uint_32 png_get_gAMA_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_charpp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP +\fBpng_byte png_get_header_ver (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_byte png_get_header_version (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_hIST (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_iCCP (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_bytepp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP \fI\fB @@ -168,11 +198,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_uint_32 png_get_image_height (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_image_height (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_image_width (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_image_width (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB @@ -180,7 +210,15 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_byte png_get_interlace_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_byte png_get_interlace_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_const_bytep png_get_io_chunk_name (png_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_io_chunk_type (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -188,77 +226,105 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_byte png_get_libpng_ver (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_io_state (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_mem_ptr(png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP +\fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP +\fBpng_uint_32 png_get_oFFs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP +\fBpng_uint_32 png_get_pCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP \fI\fB -\fBfloat png_get_pixel_aspect_ratio (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_pHYs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBfloat png_get_pixel_aspect_ratio (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_progressive_ptr (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_pHYs_dpi (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP +\fBpng_fixed_point png_get_pixel_aspect_ratio_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_rgb_to_gray_status (png_structp \fIpng_ptr) +\fBpng_uint_32 png_get_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP -\fBpng_uint_32 png_get_rowbytes (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fI\fB + +\fBpng_uint_32 png_get_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_voidp png_get_progressive_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_PLTE (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP + +\fI\fB + +\fBpng_byte png_get_rgb_to_gray_status (png_const_structp \fIpng_ptr) + +\fBpng_uint_32 png_get_rowbytes (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_bytepp png_get_rows (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_bytepp png_get_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_sBIT (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP +\fBvoid png_get_sCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, double* \fP\fIwidth\fP\fB, double* \fIheight\fP\fB);\fP \fI\fB -\fBpng_bytep png_get_signature (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBvoid png_get_sCAL_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_fixed_pointp \fP\fIwidth\fP\fB, png_fixed_pointp \fIheight\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP +\fBvoid png_get_sCAL_s (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_charpp \fP\fIwidth\fP\fB, png_charpp \fIheight\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fI*intent\fP\fB);\fP +\fBpng_bytep png_get_signature (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP +\fBpng_uint_32 png_get_sPLT (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP +\fBpng_uint_32 png_get_sRGB (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int \fI*file_srgb_intent\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_color\fP\fB);\fP +\fBpng_uint_32 png_get_text (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_tIME (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_tRNS (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans_alpha\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_color\fP\fB);\fP \fI\fB @@ -268,7 +334,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_uint_32 png_get_uint_31 (png_bytep \fIbuf\fP\fB);\fP +\fBpng_uint_32 png_get_uint_31 (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIbuf\fP\fB);\fP \fI\fB @@ -278,51 +344,75 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_uint_32 png_get_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP +\fBpng_uint_32 png_get_unknown_chunks (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP + +\fI\fB + +\fBpng_voidp png_get_user_chunk_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_user_height_max (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_voidp png_get_user_transform_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_user_width_max (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_user_chunk_ptr (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_valid (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_user_height_max( png_structp \fIpng_ptr\fP\fB);\fP +\fBfloat png_get_x_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_user_transform_ptr (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_fixed_point png_get_x_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_user_width_max (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_int_32 png_get_x_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_valid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP +\fBpng_int_32 png_get_x_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_int_32 png_get_x_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_x_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_int_32 png_get_x_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_x_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_x_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBfloat png_get_y_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_int_32 png_get_y_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_fixed_point png_get_y_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_int_32 png_get_y_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_int_32 png_get_y_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_y_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_int_32 png_get_y_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_y_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_y_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB @@ -330,23 +420,31 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_info_init_3 (png_infopp \fP\fIinfo_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP + +\fI\fB + \fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP \fI\fB +\fBvoid png_longjmp (png_structp \fP\fIpng_ptr\fP\fB, int \fIval\fP\fB);\fP + +\fI\fB + \fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP \fI\fB -\fBpng_voidp png_malloc_default(png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP +\fBpng_voidp png_malloc_default (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP \fI\fB -\fBvoidp png_memcpy (png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_size_t \fIsize\fP\fB);\fP +\fBpng_voidp png_malloc_warn (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP \fI\fB -\fBvoidp png_memset (png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_size_t \fIsize\fP\fB);\fP +\fBpng_uint_32 png_permit_mng_features (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fImng_features_permitted\fP\fB);\fP \fI\fB @@ -354,6 +452,14 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBpng_size_t png_process_data_pause \fP\fI(png_structp\fP\fB, int \fIsave\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_process_data_skip \fI(png_structp\fP\fB);\fP + +\fI\fB + \fBvoid png_progressive_combine_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIold_row\fP\fB, png_bytep \fInew_row\fP\fB);\fP \fI\fB @@ -386,7 +492,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP +\fBint png_reset_zstream (png_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBvoid png_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP \fI\fB @@ -406,6 +516,14 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_background_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, png_uint_32 \fIbackground_gamma\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_benign_errors (png_structp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP + +\fI\fB + \fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -450,10 +568,6 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_dither (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_dither\fP\fB);\fP - -\fI\fB - \fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP \fI\fB @@ -462,7 +576,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_expand_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_expand_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -478,6 +592,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_filter_heuristics_fixed (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_fixed_point_p \fP\fIfilter_weights\fP\fB, png_fixed_point_p \fIfilter_costs\fP\fB);\fP + +\fI\fB + \fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP \fI\fB @@ -486,6 +604,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_gamma_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIscreen_gamma\fP\fB, png_uint_32 \fIdefault_file_gamma\fP\fB);\fP + +\fI\fB + \fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP \fI\fB @@ -494,7 +616,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -506,7 +628,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_charp \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP +\fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_const_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_const_bytep \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP \fI\fB @@ -538,7 +660,15 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_mem_fn(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP +\fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_compression_buffer_size (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_mem_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP \fI\fB @@ -554,7 +684,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_palette_to_rgb(png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_palette_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -574,6 +704,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_quantize (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_quantize\fP\fB);\fP + +\fI\fB + \fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP \fI\fB @@ -582,6 +716,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP + +\fI\fB + \fBvoid png_set_read_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIread_user_transform_fn\fP\fB);\fP \fI\fB @@ -590,7 +728,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_fixed_point \fP\fIred\fP\fB, png_fixed_point \fIgreen\fP\fB);\fP +\fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_uint_32 \fP\fIred\fP\fB, png_uint_32 \fIgreen\fP\fB);\fP \fI\fB @@ -602,7 +740,15 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP +\fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_sCAL_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_fixed_point \fP\fIwidth\fP\fB, png_fixed_point \fIheight\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_sCAL_s (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_charp \fP\fIwidth\fP\fB, png_charp \fIheight\fP\fB);\fP \fI\fB @@ -618,11 +764,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP +\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP \fI\fB -\fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP +\fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP \fI\fB @@ -634,6 +780,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_strip_error_numbers (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIstrip_mode\fP\fB);\fP + +\fI\fB + \fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -650,11 +800,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_color\fP\fB);\fP +\fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans_alpha\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_color\fP\fB);\fP \fI\fB -\fBvoid png_set_tRNS_to_alpha(png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_tRNS_to_alpha (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -662,11 +812,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_unknown_chunk_location(png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP - -\fI\fB - -\fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP +\fBvoid png_set_unknown_chunk_location (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP \fI\fB @@ -690,10 +836,6 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_compression_buffer_size(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP - -\fI\fB - \fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, png_size_t \fP\fIstart\fP\fB, png_size_t \fInum_to_check\fP\fB);\fP \fI\fB @@ -773,14 +915,14 @@ library supports encoding, decoding, and various manipulations of the Portable Network Graphics (PNG) format image files. It uses the .IR zlib(3) compression library. -Following is a copy of the libpng.txt file that accompanies libpng. +Following is a copy of the libpng-manual.txt file that accompanies libpng. .SH LIBPNG.TXT -libpng.txt - A description on how to use and modify libpng +libpng-manual.txt - A description on how to use and modify libpng - libpng version 1.4.0 - January 3, 2010 + libpng version 1.5.1 - February 3, 2011 Updated and distributed by Glenn Randers-Pehrson <glennrp at users.sourceforge.net> - Copyright (c) 1998-2009 Glenn Randers-Pehrson + Copyright (c) 1998-2011 Glenn Randers-Pehrson This document is released under the libpng license. For conditions of distribution and use, see the disclaimer @@ -788,9 +930,9 @@ libpng.txt - A description on how to use and modify libpng Based on: - libpng versions 0.97, January 1998, through 1.4.0 - January 3, 2010 + libpng versions 0.97, January 1998, through 1.5.1 - February 3, 2011 Updated and distributed by Glenn Randers-Pehrson - Copyright (c) 1998-2009 Glenn Randers-Pehrson + Copyright (c) 1998-2011 Glenn Randers-Pehrson libpng 1.0 beta 6 version 0.96 May 28, 1997 Updated and distributed by Andreas Dilger @@ -876,34 +1018,181 @@ same instance of a structure. .SH II. Structures There are two main structures that are important to libpng, png_struct -and png_info. The first, png_struct, is an internal structure that -will not, for the most part, be used by a user except as the first -variable passed to every libpng function call. +and png_info. Both are internal structures that are no longer exposed +in the libpng interface (as of libpng 1.5.0). The png_info structure is designed to provide information about the PNG file. At one time, the fields of png_info were intended to be directly accessible to the user. However, this tended to cause problems with applications using dynamically loaded libraries, and as a result a set of interface functions for png_info (the png_get_*() and png_set_*() -functions) was developed. The fields of png_info are still available for -older applications, but it is suggested that applications use the new -interfaces if at all possible. - -Applications that do make direct access to the members of png_struct (except -for png_ptr->jmpbuf) must be recompiled whenever the library is updated, -and applications that make direct access to the members of png_info must -be recompiled if they were compiled or loaded with libpng version 1.0.6, -in which the members were in a different order. In version 1.0.7, the -members of the png_info structure reverted to the old order, as they were -in versions 0.97c through 1.0.5. Starting with version 2.0.0, both -structures are going to be hidden, and the contents of the structures will -only be accessible through the png_get/png_set functions. +functions) was developed. + +The png_struct structure is the object used by the library to decode a +single image. As of 1.5.0 this structure is also not exposed. + +Almost all libpng APIs require a pointer to a png_struct as the first argument. +Many (in particular the png_set and png_get APIs) also require a pointer +to png_info as the second argument. Some application visible macros +defined in png.h designed for basic data access (reading and writing +integers in the PNG format) break this rule, but it's almost always safe +to assume that a (png_struct*) has to be passed to call an API function. The png.h header file is an invaluable reference for programming with libpng. And while I'm on the topic, make sure you include the libpng header file: #include <png.h> +.SS Types + +The png.h header file defines a number of integral types used by the +APIs. Most of these are fairly obvious; for example types corresponding +to integers of particular sizes and types for passing color values. + +One exception is how non-integral numbers are handled. For application +convenience most APIs that take such numbers have C (double) arguments, +however internally PNG, and libpng, use 32 bit signed integers and encode +the value by multiplying by 100,000. As of libpng 1.5.0 a convenience +macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point) +which is simply (png_int_32). + +All APIs that take (double) arguments also have an matching API that +takes the corresponding fixed point integer arguments. The fixed point +API has the same name as the floating point one with _fixed appended. +The actual range of values permitted in the APIs is frequently less than +the full range of (png_fixed_point) (-21474 to +21474). When APIs require +a non-negative argument the type is recorded as png_uint_32 above. Consult +the header file and the text below for more information. + +Special care must be take with sCAL chunk handling because the chunk itself +uses non-integral values encoded as strings containing decimal floating point +numbers. See the comments in the header file. + +.SS Configuration + +The main header file function declarations are frequently protected by C +preprocessing directives of the form: + + #ifdef PNG_feature_SUPPORTED + declare-function + #endif + +The library can be built without support for these APIs, although a +standard build will have all implemented APIs. Application programs +should check the feature macros before using an API for maximum +portability. From libpng 1.5.0 the feature macros set during the build +of libpng are recorded in the header file "pnglibconf.h" and this file +is always included by png.h. + +If you don't need to change the library configuration from the default skip to +the next section ("Reading"). + +Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all +of the build project files in the 'projects' directory simply copy +scripts/pnglibconf.h.prebuilt to pnglibconf.h. This means that these build +systems do not permit easy auto-configuration of the library - they only +support the default configuration. + +The easiest way to make minor changes to the libpng configuration when +auto-configuration is supported is to add definitions to the command line +using (typically) CPPFLAGS. For example: + +CPPFLAGS=-DPNG_NO_FLOATING_ARITHMETIC + +will change the internal libpng math implementation for gamma correction and +other arithmetic calculations to fixed point, avoiding the need for fast +floating point support. The result can be seen in the generated pnglibconf.h - +make sure it contains the changed feature macro setting. + +If you need to make more extensive configuration changes - more than one or two +feature macro settings - you can either add -DPNG_USER_CONFIG to the build +command line and put a list of feature macro settings in pngusr.h or you can set +DFA_XTRA (a makefile variable) to a file containing the same information in the +form of 'option' settings. + +A. Changing pnglibconf.h + +A variety of methods exist to build libpng. Not all of these support +reconfiguration of pnglibconf.h. To reconfigure pnglibconf.h it must either be +rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand. + +Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing +the lines defining the supported features, paying very close attention to the +'option' information in scripts/pnglibconf.dfa that describes those features and +their requirements. This is easy to get wrong. + +B. Configuration using DFA_XTRA + +Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later +variant such as 'nawk' or 'gawk', is available. The configure build will +automatically find an appropriate awk and build pnglibconf.h. +scripts/pnglibconf.mak contains a set of make rules for doing the same thing if +configure is not used, and many of the makefiles in the scripts directory use +this approach. + +When rebuilding simply write new file containing changed options and set +DFA_XTRA to the name of this file. This causes the build to append the new file +to the end of scripts/pnglibconf.dfa. pngusr.dfa should contain lines of the +following forms: + +everything = off + +This turns all optional features off. Include it at the start of pngusr.dfa to +make it easier to build a minimal configuration. You will need to turn at least +some features on afterward to enable either reading or writing code, or both. + +option feature on +option feature off + +Enable or disable a single feature. This will automatically enable other +features required by a feature that is turned on or disable other features that +require a feature which is turned off. Conflicting settings will cause an error +message to be emitted by awk. + +setting feature default value + +Changes the default value of setting 'feature' to 'value'. There are a small +number of settings listed at the top of pnglibconf.h, they are documented in the +source code. Most of these values have performance implications for the library +but most of them have no visible effect on the API. Some can also be overridden +from the API. + +C. Configuration using PNG_USR_CONFIG + +If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file +pngusr.h will automatically be included before the options in +scripts/pnglibconf.dfa are processed. pngusr.h should contain only macro +definitions turning features on or off or setting settings. + +Apart from the global setting "everything = off" all the options listed above +can be set using macros in pngusr.h: + +#define PNG_feature_SUPPORTED + +is equivalent to: + +option feature on + +#define PNG_NO_feature + +is equivalent to: + +option feature off + +#define PNG_feature value + +is equivalent to: + +setting feature default value + +Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the +pngusr file you supply override the contents of scripts/pnglibconf.dfa + +If confusing or incomprehensible behavior results it is possible to +examine the intermediate file pnglibconf.dfn to find the full set of +dependency information for each setting and option. Simply locate the +feature in the file and read the C comments that precede it. + .SH III. Reading We'll now walk you through the possible functions to call when reading @@ -939,13 +1228,15 @@ Customizing libpng. FILE *fp = fopen(file_name, "rb"); if (!fp) { - return (ERROR); + return (ERROR); } + fread(header, 1, number, fp); is_png = !png_sig_cmp(header, 0, number); + if (!is_png) { - return (NOT_PNG); + return (NOT_PNG); } @@ -961,29 +1252,32 @@ The structure allocation functions quietly return NULL if they fail to create the structure, so your application should check for that. png_structp png_ptr = png_create_read_struct - (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, + (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, user_error_fn, user_warning_fn); + if (!png_ptr) - return (ERROR); + return (ERROR); png_infop info_ptr = png_create_info_struct(png_ptr); + if (!info_ptr) { - png_destroy_read_struct(&png_ptr, + png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL); - return (ERROR); + return (ERROR); } png_infop end_info = png_create_info_struct(png_ptr); + if (!end_info) { - png_destroy_read_struct(&png_ptr, &info_ptr, + png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); - return (ERROR); + return (ERROR); } If you want to use your own memory allocation routines, -define PNG_USER_MEM_SUPPORTED and use +use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use png_create_read_struct_2() instead of png_create_read_struct(): png_structp png_ptr = png_create_read_struct_2 @@ -1011,16 +1305,20 @@ free any memory. if (setjmp(png_jmpbuf(png_ptr))) { - png_destroy_read_struct(&png_ptr, &info_ptr, + png_destroy_read_struct(&png_ptr, &info_ptr, &end_info); - fclose(fp); - return (ERROR); + fclose(fp); + return (ERROR); } If you would rather avoid the complexity of setjmp/longjmp issues, -you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case +you can compile libpng with PNG_NO_SETJMP, in which case errors will result in a call to PNG_ABORT() which defaults to abort(). +You can #define PNG_ABORT() to a function that does something +more useful than abort(), as long as your function does not +return. + Now you need to set up the input code. The default for libpng is to use the C function fread(). If you use this, you will need to pass a valid FILE * in the function png_init_io(). Be sure that the file is @@ -1037,12 +1335,46 @@ libpng know that there are some bytes missing from the start of the file. png_set_sig_bytes(png_ptr, number); +You can change the zlib compression buffer size to be used while +reading compressed data with + + png_set_compression_buffer_size(png_ptr, buffer_size); + +where the default size is 8192 bytes. Note that the buffer size +is changed immediately and the buffer is reallocated immediately, +instead of setting a flag to be acted upon later. + +If you want CRC errors to be handled in a different manner than +the default, use + + png_set_crc_action(png_ptr, crit_action, ancil_action); + +The values for png_set_crc_action() say how libpng is to handle CRC errors in +ancillary and critical chunks, and whether to use the data contained +therein. Note that it is impossible to "discard" data in a critical +chunk. + +Choices for (int) crit_action are + PNG_CRC_DEFAULT 0 error/quit + PNG_CRC_ERROR_QUIT 1 error/quit + PNG_CRC_WARN_USE 3 warn/use data + PNG_CRC_QUIET_USE 4 quiet/use data + PNG_CRC_NO_CHANGE 5 use the current value + +Choices for (int) ancil_action are + PNG_CRC_DEFAULT 0 error/quit + PNG_CRC_ERROR_QUIT 1 error/quit + PNG_CRC_WARN_DISCARD 2 warn/discard data + PNG_CRC_WARN_USE 3 warn/use data + PNG_CRC_QUIET_USE 4 quiet/use data + PNG_CRC_NO_CHANGE 5 use the current value + .SS Setting up callback code You can set up a callback function to handle any unknown chunks in the input stream. You must supply the function - read_chunk_callback(png_ptr ptr, + read_chunk_callback(png_structp png_ptr, png_unknown_chunkp chunk); { /* The unknown chunk structure contains your @@ -1088,8 +1420,8 @@ called after each row has been read, which you can use to control a progress meter or the like. It's demonstrated in pngtest.c. You must supply a function - void read_row_callback(png_ptr ptr, png_uint_32 row, - int pass); + void read_row_callback(png_structp png_ptr, + png_uint_32 row, int pass); { /* put your code here */ } @@ -1115,14 +1447,17 @@ chunk types. To change this, you can call: 1: ignore; do not keep 2: keep only if safe-to-copy 3: keep even if unsafe-to-copy + You can use these definitions: PNG_HANDLE_CHUNK_AS_DEFAULT 0 PNG_HANDLE_CHUNK_NEVER 1 PNG_HANDLE_CHUNK_IF_SAFE 2 PNG_HANDLE_CHUNK_ALWAYS 3 + chunk_list - list of chunks affected (a byte string, five bytes per chunk, NULL or '\0' if num_chunks is 0) + num_chunks - number of chunks affected; if 0, all unknown chunks are affected. If nonzero, only the chunks in the list are affected @@ -1158,8 +1493,10 @@ callback function: #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) /* ignore all unknown chunks: */ png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0); + /* except for vpAg: */ png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1); + /* also ignore unused known chunks: */ png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks, (int)sizeof(unused_chunks)/5); @@ -1200,6 +1537,18 @@ where 0x7fffffffL means unlimited. You can retrieve this limit with This limit also applies to the number of buffers that can be allocated by png_decompress_chunk() while decompressing iTXt, zTXt, and iCCP chunks. +You can also set a limit on the amount of memory that a compressed chunk +other than IDAT can occupy, with + + png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max); + +and you can retrieve the limit with + + chunk_malloc_max = png_get_chunk_malloc_max(png_ptr); + +Any chunks that would cause either of these limits to be exceeded will +be ignored. + .SS The high-level read interface At this point there are two ways to proceed; through the high-level @@ -1231,7 +1580,7 @@ you want to do are limited to the following set: to RGB (or GA to RGBA) (This excludes setting a background color, doing gamma transformation, -dithering, and setting filler.) If this is the case, simply do this: +quantizing, and setting filler.) If this is the case, simply do this: png_read_png(png_ptr, info_ptr, png_transforms, NULL) @@ -1260,17 +1609,22 @@ row_pointers prior to calling png_read_png() with if (height > PNG_UINT_32_MAX/png_sizeof(png_byte)) png_error (png_ptr, - "Image is too tall to process in memory"); + "Image is too tall to process in memory"); + if (width > PNG_UINT_32_MAX/pixel_size) png_error (png_ptr, - "Image is too wide to process in memory"); + "Image is too wide to process in memory"); + row_pointers = png_malloc(png_ptr, - height*png_sizeof(png_bytep)); + height*png_sizeof(png_bytep)); + for (int i=0; i<height, i++) row_pointers[i]=NULL; /* security precaution */ + for (int i=0; i<height, i++) row_pointers[i]=png_malloc(png_ptr, - width*pixel_size); + width*pixel_size); + png_set_rows(png_ptr, info_ptr, &row_pointers); Alternatively you could allocate your image in one big block and define @@ -1280,7 +1634,7 @@ If you use png_set_rows(), the application is responsible for freeing row_pointers (and row_pointers[i], if they were separately allocated). If you don't allocate row_pointers ahead of time, png_read_png() will -do it, and it'll be free'ed when you call png_destroy_*(). +do it, and it'll be free'ed by libpng when you call png_destroy_*(). .SS The low-level read interface @@ -1304,13 +1658,16 @@ in until png_read_end() has read the chunk data following the image. width - holds the width of the image in pixels (up to 2^31). + height - holds the height of the image in pixels (up to 2^31). + bit_depth - holds the bit depth of one of the image channels. (valid values are 1, 2, 4, 8, 16 and depend also on the color_type. See also significant bits (sBIT) below). + color_type - describes which color/alpha channels are present. PNG_COLOR_TYPE_GRAY @@ -1328,15 +1685,17 @@ in until png_read_end() has read the chunk data following the image. PNG_COLOR_MASK_COLOR PNG_COLOR_MASK_ALPHA + interlace_type - (PNG_INTERLACE_NONE or + PNG_INTERLACE_ADAM7) + + compression_type - (must be PNG_COMPRESSION_TYPE_BASE + for PNG 1.0) + filter_method - (must be PNG_FILTER_TYPE_BASE for PNG 1.0, and can also be PNG_INTRAPIXEL_DIFFERENCING if the PNG datastream is embedded in a MNG-1.0 datastream) - compression_type - (must be PNG_COMPRESSION_TYPE_BASE - for PNG 1.0) - interlace_type - (PNG_INTERLACE_NONE or - PNG_INTERLACE_ADAM7) Any or all of interlace_type, compression_type, or filter_method can be NULL if you are @@ -1351,28 +1710,38 @@ in until png_read_end() has read the chunk data following the image. width = png_get_image_width(png_ptr, info_ptr); + height = png_get_image_height(png_ptr, info_ptr); + bit_depth = png_get_bit_depth(png_ptr, info_ptr); + color_type = png_get_color_type(png_ptr, info_ptr); - filter_method = png_get_filter_type(png_ptr, + + interlace_type = png_get_interlace_type(png_ptr, info_ptr); + compression_type = png_get_compression_type(png_ptr, info_ptr); - interlace_type = png_get_interlace_type(png_ptr, + + filter_method = png_get_filter_type(png_ptr, info_ptr); channels = png_get_channels(png_ptr, info_ptr); + channels - number of channels of info for the color type (valid values are 1 (GRAY, PALETTE), 2 (GRAY_ALPHA), 3 (RGB), 4 (RGB_ALPHA or RGB + filler byte)) + rowbytes = png_get_rowbytes(png_ptr, info_ptr); + rowbytes - number of bytes needed to hold a row signature = png_get_signature(png_ptr, info_ptr); + signature - holds the signature read from the file (if any). The data is kept in the same offset it would be if the @@ -1392,16 +1761,24 @@ pointer into the info_ptr is returned for any complex types. png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette); + palette - the palette for the file (array of png_color) + num_palette - number of entries in the palette - png_get_gAMA(png_ptr, info_ptr, &gamma); - gamma - the gamma the file is written - at (PNG_INFO_gAMA) + png_get_gAMA(png_ptr, info_ptr, &file_gamma); + png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma); + + file_gamma - the gamma at which the file is + written (PNG_INFO_gAMA) + + int_file_gamma - 100,000 times the gamma at which the + file is written png_get_sRGB(png_ptr, info_ptr, &srgb_intent); - srgb_intent - the rendering intent (PNG_INFO_sRGB) + + file_srgb_intent - the rendering intent (PNG_INFO_sRGB) The presence of the sRGB chunk means that the pixel data is in the sRGB color space. This chunk also @@ -1410,16 +1787,21 @@ pointer into the info_ptr is returned for any complex types. png_get_iCCP(png_ptr, info_ptr, &name, &compression_type, &profile, &proflen); - name - The profile name. - compression - The compression type; always - PNG_COMPRESSION_TYPE_BASE for PNG 1.0. - You may give NULL to this argument to - ignore it. - profile - International Color Consortium color - profile data. May contain NULs. - proflen - length of profile data in bytes. + + name - The profile name. + + compression_type - The compression type; always + PNG_COMPRESSION_TYPE_BASE for PNG 1.0. + You may give NULL to this argument to + ignore it. + + profile - International Color Consortium color + profile data. May contain NULs. + + proflen - length of profile data in bytes. png_get_sBIT(png_ptr, info_ptr, &sig_bit); + sig_bit - the number of significant bits for (PNG_INFO_sBIT) each of the gray, red, green, and blue channels, @@ -1428,50 +1810,66 @@ pointer into the info_ptr is returned for any complex types. png_get_tRNS(png_ptr, info_ptr, &trans_alpha, &num_trans, &trans_color); + trans_alpha - array of alpha (transparency) entries for palette (PNG_INFO_tRNS) + + num_trans - number of transparent entries + (PNG_INFO_tRNS) + trans_color - graylevel or color sample values of the single transparent color for non-paletted images (PNG_INFO_tRNS) - num_trans - number of transparent entries - (PNG_INFO_tRNS) png_get_hIST(png_ptr, info_ptr, &hist); (PNG_INFO_hIST) + hist - histogram of palette (array of png_uint_16) png_get_tIME(png_ptr, info_ptr, &mod_time); + mod_time - time image was last modified (PNG_VALID_tIME) png_get_bKGD(png_ptr, info_ptr, &background); + background - background color (PNG_VALID_bKGD) valid 16-bit red, green and blue values, regardless of color_type num_comments = png_get_text(png_ptr, info_ptr, &text_ptr, &num_text); + num_comments - number of comments + text_ptr - array of png_text holding image comments + text_ptr[i].compression - type of compression used on "text" PNG_TEXT_COMPRESSION_NONE PNG_TEXT_COMPRESSION_zTXt PNG_ITXT_COMPRESSION_NONE PNG_ITXT_COMPRESSION_zTXt + text_ptr[i].key - keyword for comment. Must contain 1-79 characters. + text_ptr[i].text - text comments for current keyword. Can be empty. + text_ptr[i].text_length - length of text string, after decompression, 0 for iTXt + text_ptr[i].itxt_length - length of itxt string, after decompression, 0 for tEXt/zTXt + text_ptr[i].lang - language of comment (empty string for unknown). + text_ptr[i].lang_key - keyword in UTF-8 (empty string for unknown). + Note that the itxt_length, lang, and lang_key members of the text_ptr structure only exist when the library is built with iTXt chunk support. @@ -1479,6 +1877,7 @@ pointer into the info_ptr is returned for any complex types. num_text - number of comments (same as num_comments; you can put NULL here to avoid the duplication) + Note while png_set_text() will accept text, language, and translated keywords that can be NULL pointers, the structure returned by png_get_text will always contain @@ -1487,49 +1886,68 @@ pointer into the info_ptr is returned for any complex types. num_spalettes = png_get_sPLT(png_ptr, info_ptr, &palette_ptr); + + num_spalettes - number of sPLT chunks read. + palette_ptr - array of palette structures holding contents of one or more sPLT chunks read. - num_spalettes - number of sPLT chunks read. png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y, &unit_type); + offset_x - positive offset from the left edge of the screen + offset_y - positive offset from the top edge of the screen + unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, &unit_type); + res_x - pixels/unit physical resolution in x direction + res_y - pixels/unit physical resolution in x direction + unit_type - PNG_RESOLUTION_UNKNOWN, PNG_RESOLUTION_METER png_get_sCAL(png_ptr, info_ptr, &unit, &width, &height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units (width and height are doubles) png_get_sCAL_s(png_ptr, info_ptr, &unit, &width, &height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units (width and height are strings like "2.54") num_unknown_chunks = png_get_unknown_chunks(png_ptr, info_ptr, &unknowns) + unknowns - array of png_unknown_chunk structures holding unknown chunks + unknowns[i].name - name of unknown chunk + unknowns[i].data - data of unknown chunk + unknowns[i].size - size of unknown chunk's data + unknowns[i].location - position of chunk in file The value of "i" corresponds to the order in which the @@ -1541,34 +1959,55 @@ forms: res_x = png_get_x_pixels_per_meter(png_ptr, info_ptr) + res_y = png_get_y_pixels_per_meter(png_ptr, info_ptr) + res_x_and_y = png_get_pixels_per_meter(png_ptr, info_ptr) + res_x = png_get_x_pixels_per_inch(png_ptr, info_ptr) + res_y = png_get_y_pixels_per_inch(png_ptr, info_ptr) + res_x_and_y = png_get_pixels_per_inch(png_ptr, info_ptr) + aspect_ratio = png_get_pixel_aspect_ratio(png_ptr, info_ptr) - (Each of these returns 0 [signifying "unknown"] if + Each of these returns 0 [signifying "unknown"] if the data is not present or if res_x is 0; - res_x_and_y is 0 if res_x != res_y) + res_x_and_y is 0 if res_x != res_y + + Note that because of the way the resolutions are + stored internally, the inch conversions won't + come out to exactly even number. For example, + 72 dpi is stored as 0.28346 pixels/meter, and + when this is retrieved it is 71.9988 dpi, so + be sure to round the returned value appropriately + if you want to display a reasonable-looking result. The data from the oFFs chunk can be retrieved in several convenient forms: x_offset = png_get_x_offset_microns(png_ptr, info_ptr); + y_offset = png_get_y_offset_microns(png_ptr, info_ptr); + x_offset = png_get_x_offset_inches(png_ptr, info_ptr); + y_offset = png_get_y_offset_inches(png_ptr, info_ptr); - (Each of these returns 0 [signifying "unknown" if both + Each of these returns 0 [signifying "unknown" if both x and y are 0] if the data is not present or if the - chunk is present but the unit is the pixel) + chunk is present but the unit is the pixel. The + remark about inexact inch conversions applies here + as well, because a value in inches can't always be + converted to microns and back without some loss + of precision. For more information, see the png_info definition in png.h and the PNG specification for chunk contents. Be careful with trusting @@ -1655,7 +2094,7 @@ things. As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was added. It expands the sample depth without changing tRNS to alpha. -As of libpng version 1.4.0, not all possible expansions are supported. +As of libpng version 1.5.1, not all possible expansions are supported. In the following table, the 01 means grayscale with depth<8, 31 means indexed with depth<8, other numerals represent the color type, "T" means @@ -1696,7 +2135,7 @@ PNG can have files with 16 bits per channel. If you only can handle 8 bits per channel, this will strip the pixels down to 8 bit. if (bit_depth == 16) - png_set_strip_16(png_ptr); + png_set_strip_16(png_ptr); If, for some reason, you don't need the alpha channel on an image, and you want to remove it rather than combining it with the background @@ -1704,7 +2143,7 @@ and you want to remove it rather than combining it with the background it with the background, so that's what you should probably do): if (color_type & PNG_COLOR_MASK_ALPHA) - png_set_strip_alpha(png_ptr); + png_set_strip_alpha(png_ptr); In PNG files, the alpha channel in an image is the level of opacity. If you need the alpha channel in an image to @@ -1721,7 +2160,7 @@ files. This code expands to 1 pixel per byte without changing the values of the pixels: if (bit_depth < 8) - png_set_packing(png_ptr); + png_set_packing(png_ptr); PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels stored in a PNG image have been "scaled" or "shifted" up to the next @@ -1733,20 +2172,20 @@ image. This call reduces the pixels back down to the original bit depth: png_color_8p sig_bit; if (png_get_sBIT(png_ptr, info_ptr, &sig_bit)) - png_set_shift(png_ptr, sig_bit); + png_set_shift(png_ptr, sig_bit); PNG files store 3-color pixels in red, green, blue order. This code changes the storage of the pixels to blue, green, red: if (color_type == PNG_COLOR_TYPE_RGB || color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_bgr(png_ptr); + png_set_bgr(png_ptr); PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them into 4 or 8 bytes for windowing systems that need them in this format: if (color_type == PNG_COLOR_TYPE_RGB) - png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); + png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); where "filler" is the 8 or 16-bit number to fill with, and the location is either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether @@ -1759,8 +2198,8 @@ Note that png_set_filler() does not change the color type. If you want to do that, you can add a true alpha channel with if (color_type == PNG_COLOR_TYPE_RGB || - color_type == PNG_COLOR_TYPE_GRAY) - png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); + color_type == PNG_COLOR_TYPE_GRAY) + png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); where "filler" contains the alpha value to assign to each pixel. This function was added in libpng-1.2.7. @@ -1769,33 +2208,36 @@ If you are reading an image with an alpha channel, and you need the data as ARGB instead of the normal PNG format RGBA: if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_swap_alpha(png_ptr); + png_set_swap_alpha(png_ptr); For some uses, you may want a grayscale image to be represented as RGB. This code will do that conversion: if (color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_GRAY_ALPHA) - png_set_gray_to_rgb(png_ptr); + png_set_gray_to_rgb(png_ptr); Conversely, you can convert an RGB or RGBA image to grayscale or grayscale with alpha. if (color_type == PNG_COLOR_TYPE_RGB || color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_rgb_to_gray_fixed(png_ptr, error_action, - int red_weight, int green_weight); + png_set_rgb_to_gray_fixed(png_ptr, error_action, + int red_weight, int green_weight); error_action = 1: silently do the conversion + error_action = 2: issue a warning if the original image has any pixel where red != green or red != blue + error_action = 3: issue an error and abort the conversion if the original image has any pixel where red != green or red != blue red_weight: weight of red component times 100000 + green_weight: weight of green component times 100000 If either weight is negative, default weights (21268, 71514) are used. @@ -1822,16 +2264,12 @@ Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net> Y = 0.212671 * R + 0.715160 * G + 0.072169 * B -Libpng approximates this with - - Y = 0.21268 * R + 0.7151 * G + 0.07217 * B - -which can be expressed with integers as +Libpng approximates this with integers scaled by 32768: - Y = (6969 * R + 23434 * G + 2365 * B)/32768 + Y = (6968 * R + 23434 * G + 2366 * B)/32768 The calculation is done in a linear colorspace, if the image gamma -is known. +can be determined. If you have a grayscale and you are using png_set_expand_depth(), png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to @@ -1846,11 +2284,11 @@ or as an RGB triplet that may or may not be in the palette (need_expand = 0). png_color_16p image_background; if (png_get_bKGD(png_ptr, info_ptr, &image_background)) - png_set_background(png_ptr, image_background, - PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); + png_set_background(png_ptr, image_background, + PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); else - png_set_background(png_ptr, &my_background, - PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); + png_set_background(png_ptr, &my_background, + PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); The png_set_background() function tells libpng to composite images with alpha or simple transparency against the supplied background @@ -1883,6 +2321,7 @@ a slightly smaller exponent is better. { screen_gamma = user_defined_screen_gamma; } + /* One way that applications can share the same screen gamma value */ else if ((gamma_str = getenv("SCREEN_GAMMA")) @@ -1890,18 +2329,22 @@ a slightly smaller exponent is better. { screen_gamma = (double)atof(gamma_str); } + /* If we don't have another value */ else { screen_gamma = 2.2; /* A good guess for a PC monitor in a bright office or a dim room */ + screen_gamma = 2.0; /* A good guess for a PC monitor in a dark room */ + screen_gamma = 1.7 or 1.0; /* A good guess for Mac systems */ } -The png_set_gamma() function handles gamma transformations of the data. +The functions png_set_gamma() and its fixed point equivalent +png_set_gamma_fixed() handle gamma transformations of the data. Pass both the file gamma and the current screen_gamma. If the file does not have a gamma value, you can pass one anyway if you have an idea what it is (usually 0.45455 is a good guess for GIF images on PCs). Note @@ -1910,11 +2353,47 @@ on gamma in the PNG specification for an excellent description of what gamma is, and why all applications should support it. It is strongly recommended that PNG viewers support gamma correction. - if (png_get_gAMA(png_ptr, info_ptr, &gamma)) - png_set_gamma(png_ptr, screen_gamma, gamma); + if (png_get_gAMA(png_ptr, info_ptr, &file_gamma)) + png_set_gamma(png_ptr, screen_gamma, file_gamma); + else png_set_gamma(png_ptr, screen_gamma, 0.45455); +If you need to reduce an RGB file to a paletted file, or if a paletted +file has more entries then will fit on your screen, png_set_quantize() +will do that. Note that this is a simple match quantization that merely +finds the closest color available. This should work fairly well with +optimized palettes, but fairly badly with linear color cubes. If you +pass a palette that is larger then maximum_colors, the file will +reduce the number of colors in the palette so it will fit into +maximum_colors. If there is a histogram, it will use it to make +more intelligent choices when reducing the palette. If there is no +histogram, it may not do as good a job. + + if (color_type & PNG_COLOR_MASK_COLOR) + { + if (png_get_valid(png_ptr, info_ptr, + PNG_INFO_PLTE)) + { + png_uint_16p histogram = NULL; + + png_get_hIST(png_ptr, info_ptr, + &histogram); + png_set_quantize(png_ptr, palette, num_palette, + max_screen_colors, histogram, 1); + } + + else + { + png_color std_color_cube[MAX_SCREEN_COLORS] = + { ... colors ... }; + + png_set_quantize(png_ptr, std_color_cube, + MAX_SCREEN_COLORS, MAX_SCREEN_COLORS, + NULL,0); + } + } + PNG files describe monochrome as black being zero and white being one. The following code will reverse this (make black be one and white be zero): @@ -1925,7 +2404,7 @@ zero): This function can also be used to invert grayscale and gray-alpha images: if (color_type == PNG_COLOR_TYPE_GRAY || - color_type == PNG_COLOR_TYPE_GRAY_ALPHA) + color_type == PNG_COLOR_TYPE_GRAY_ALPHA) png_set_invert_mono(png_ptr); PNG files store 16 bit pixels in network byte order (big-endian, @@ -1934,7 +2413,7 @@ other way (little-endian, i.e. least significant bits first, the way PCs store them): if (bit_depth == 16) - png_set_swap(png_ptr); + png_set_swap(png_ptr); If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you need to change the order the pixels are packed into bytes, you can use: @@ -1947,15 +2426,28 @@ the existing ones meets your needs. This is done by setting a callback with png_set_read_user_transform_fn(png_ptr, - read_transform_fn); + read_transform_fn); You must supply the function - void read_transform_fn(png_ptr ptr, row_info_ptr - row_info, png_bytep data) + void read_transform_fn(png_structp png_ptr, row_info_ptr + row_info, png_bytep data) See pngtest.c for a working example. Your function will be called -after all of the other transformations have been processed. +after all of the other transformations have been processed. Take care with +interlaced images if you do the interlace yourself - the width of the row is the +width in 'row_info', not the overall image width. + +If supported libpng provides two information routines that you can use to find +where you are in processing the image: + + png_get_current_pass_number(png_structp png_ptr); + png_get_current_row_number(png_structp png_ptr); + +Don't try using these outside a transform callback - firstly they are only +supported if user transforms are supported, secondly they may well return +unexpected results unless the row is actually being processed at the moment they +are called. You can also set up a pointer to a user structure for use by your callback function, and you can inform libpng that your transform @@ -1963,7 +2455,7 @@ function will change the number of channels or bit depth with the function png_set_user_transform_info(png_ptr, user_ptr, - user_depth, user_channels); + user_depth, user_channels); The user's application, not libpng, is responsible for allocating and freeing any memory required for the user structure. @@ -1972,7 +2464,7 @@ You can retrieve the pointer via the function png_get_user_transform_ptr(). For example: voidp read_user_transform_ptr = - png_get_user_transform_ptr(png_ptr); + png_get_user_transform_ptr(png_ptr); The last thing to handle is interlacing; this is covered in detail below, but you must call the function here if you want libpng to handle expansion @@ -1997,6 +2489,15 @@ are allocating one large chunk, you will need to build an array of pointers to each row, as it will be needed for some of the functions below. +Remember: Before you call png_read_update_info(), the png_get_ +functions return the values corresponding to the original PNG image. +After you call png_read_update_info the values refer to the image +that libpng will output. Consequently you must call all the png_set_ +functions before you call png_read_update_info(). This is particularly +important for png_set_interlace_handling() - if you are going to call +png_read_update_info() you must call png_set_interlace_handling() before +it unless you want to receive interlaced output. + .SS Reading image data After you've allocated memory, you can read the image data. @@ -2006,9 +2507,10 @@ call png_read_image() and libpng will read in all the image data and put it in the memory area supplied. You will need to pass in an array of pointers to each row. -This function automatically handles interlacing, so you don't need -to call png_set_interlace_handling() or call this function multiple -times, or any of that other stuff necessary with png_read_rows(). +This function automatically handles interlacing, so you don't +need to call png_set_interlace_handling() (unless you call +png_read_update_info()) or call this function multiple times, or any +of that other stuff necessary with png_read_rows(). png_read_image(png_ptr, row_pointers); @@ -2023,7 +2525,7 @@ use png_read_rows() instead. If there is no interlacing (check interlace_type == PNG_INTERLACE_NONE), this is simple: png_read_rows(png_ptr, row_pointers, NULL, - number_of_rows); + number_of_rows); where row_pointers is the same as in the png_read_image() call. @@ -2035,13 +2537,15 @@ a single row_pointer instead of an array of row_pointers: If the file is interlaced (interlace_type != 0 in the IHDR chunk), things get somewhat harder. The only current (PNG Specification version 1.2) -interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7) -is a somewhat complicated 2D interlace scheme, known as Adam7, that +interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7); +a somewhat complicated 2D interlace scheme, known as Adam7, that breaks down an image into seven smaller images of varying size, based -on an 8x8 grid. +on an 8x8 grid. This number is defined (from libpng 1.5) as +PNG_INTERLACE_ADAM7_PASSES in png.h libpng can fill out those images or it can give them to you "as is". -If you want them filled out, there are two ways to do that. The one +It is almost always better to have libpng handle the interlacing for you. +If you want the images filled out, there are two ways to do that. The one mentioned in the PNG specification is to expand each pixel to cover those pixels that have not been read yet (the "rectangle" method). This results in a blocky image for the first pass, which gradually @@ -2051,37 +2555,20 @@ rest of the image remaining whatever colors they were initialized to before the start of the read. The first method usually looks better, but tends to be slower, as there are more pixels to put in the rows. -If you don't want libpng to handle the interlacing details, just call -png_read_rows() seven times to read in all seven images. Each of the -images is a valid image by itself, or they can all be combined on an -8x8 grid to form a single image (although if you intend to combine them -you would be far better off using the libpng interlace handling). - -The first pass will return an image 1/8 as wide as the entire image -(every 8th column starting in column 0) and 1/8 as high as the original -(every 8th row starting in row 0), the second will be 1/8 as wide -(starting in column 4) and 1/8 as high (also starting in row 0). The -third pass will be 1/4 as wide (every 4th pixel starting in column 0) and -1/8 as high (every 8th row starting in row 4), and the fourth pass will -be 1/4 as wide and 1/4 as high (every 4th column starting in column 2, -and every 4th row starting in row 0). The fifth pass will return an -image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2), -while the sixth pass will be 1/2 as wide and 1/2 as high as the original -(starting in column 1 and row 0). The seventh and final pass will be as -wide as the original, and 1/2 as high, containing all of the odd -numbered scanlines. Phew! - -If you want libpng to expand the images, call this before calling -png_start_read_image() or png_read_update_info(): +If, as is likely, you want libpng to expand the images, call this before +calling png_start_read_image() or png_read_update_info(): if (interlace_type == PNG_INTERLACE_ADAM7) - number_of_passes + number_of_passes = png_set_interlace_handling(png_ptr); -This will return the number of passes needed. Currently, this -is seven, but may change if another interlace type is added. -This function can be called even if the file is not interlaced, -where it will return one pass. +This will return the number of passes needed. Currently, this is seven, +but may change if another interlace type is added. This function can be +called even if the file is not interlaced, where it will return one pass. +You then need to read the whole image 'number_of_passes' times. Each time +will distribute the pixels from the current pass to the correct place in +the output image, so you need to supply the same rows to png_read_rows in +each pass. If you are not going to display the image after each pass, but are going to wait until the entire image is read in, use the sparkle @@ -2098,14 +2585,104 @@ not the data. Each pass only writes the pixels appropriate for that pass, and assumes the data from previous passes is still valid. png_read_rows(png_ptr, row_pointers, NULL, - number_of_rows); + number_of_rows); If you only want the first effect (the rectangles), do the same as before except pass the row buffer in the third parameter, and leave the second parameter NULL. png_read_rows(png_ptr, NULL, row_pointers, - number_of_rows); + number_of_rows); + +If you don't want libpng to handle the interlacing details, just call +png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images. +Each of the images is a valid image by itself, however you will almost +certainly need to distribute the pixels from each sub-image to the +correct place. This is where everything gets very tricky. + +If you want to retrieve the separate images you must pass the correct +number of rows to each successive call of png_read_rows(). The calculation +gets pretty complicated for small images, where some sub-images may +not even exist because either their width or height ends up zero. +libpng provides two macros to help you in 1.5 and later versions: + + png_uint_32 width = PNG_PASS_COLS(image_width, pass_number); + png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number); + +Respectively these tell you the width and height of the sub-image +corresponding to the numbered pass. 'pass' is in in the range 0 to 6 - +this can be confusing because the specification refers to the same passes +as 1 to 7! Be careful, you must check both the width and height before +calling png_read_rows() and not call it for that pass if either is zero. + +You can, of course, read each sub-image row by row. If you want to +produce optimal code to make a pixel-by-pixel transformation of an +interlaced image this is the best approach; read each row of each pass, +transform it, and write it out to a new interlaced image. + +If you want to de-interlace the image yourself libpng provides further +macros to help that tell you where to place the pixels in the output image. +Because the interlacing scheme is rectangular - sub-image pixels are always +arranged on a rectangular grid - all you need to know for each pass is the +starting column and row in the output image of the first pixel plus the +spacing between each pixel. As of libpng 1.5 there are four macros to +retrieve this information: + + png_uint_32 x = PNG_PASS_START_COL(pass); + png_uint_32 y = PNG_PASS_START_ROW(pass); + png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass); + png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass); + +These allow you to write the obvious loop: + + png_uint_32 input_y = 0; + png_uint_32 output_y = PNG_PASS_START_ROW(pass); + + while (output_y < output_image_height) + { + png_uint_32 input_x = 0; + png_uint_32 output_x = PNG_PASS_START_COL(pass); + + while (output_x < output_image_width) + { + image[output_y][output_x] = + subimage[pass][input_y][input_x++]; + + output_x += xStep; + } + + ++input_y; + output_y += yStep; + } + +Notice that the steps between successive output rows and columns are +returned as shifts. This is possible because the pixels in the subimages +are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original +image. In practice you may need to directly calculate the output coordinate +given an input coordinate. libpng provides two further macros for this +purpose: + + png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass); + png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass); + +Finally a pair of macros are provided to tell you if a particular image +row or column appears in a given pass: + + int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass); + int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass); + +Bear in mind that you will probably also need to check the width and height +of the pass in addition to the above to be sure the pass even exists! + +With any luck you are convinced by now that you don't want to do your own +interlace handling. In reality normally the only good reason for doing this +is if you are processing PNG files on a pixel-by-pixel basis and don't want +to load the whole file into memory when it is interlaced. + +libpng includes a test program, pngvalid, that illustrates reading and +writing of interlaced images. If you can't get interlacing to work in your +code and don't want to leave it to libpng (the recommended approach) see +how pngvalid.c does it. .SS Finishing a sequential read @@ -2127,6 +2704,7 @@ It is also possible to individually free the info_ptr members that point to libpng-allocated storage with the following function: png_free_data(png_ptr, info_ptr, mask, seq) + mask - identifies data to be freed, a mask containing the bitwise OR of one or more of @@ -2136,6 +2714,7 @@ point to libpng-allocated storage with the following function: PNG_FREE_SCAL, PNG_FREE_SPLT, PNG_FREE_TEXT, PNG_FREE_UNKN, or simply PNG_FREE_ALL + seq - sequence number of item to be freed (-1 for all items) @@ -2153,13 +2732,15 @@ or so that it will free data that was allocated by the user with png_malloc() or png_zalloc() and passed in via a png_set_*() function, with png_data_freer(png_ptr, info_ptr, freer, mask) - mask - which data elements are affected - same choices as in png_free_data() + freer - one of PNG_DESTROY_WILL_FREE_DATA PNG_SET_WILL_FREE_DATA PNG_USER_WILL_FREE_DATA + mask - which data elements are affected + same choices as in png_free_data() + This function only affects data that has already been allocated. You can call this function after reading the PNG data but before calling any png_set_*() functions, to control whether the user or the png_set_*() @@ -2188,6 +2769,7 @@ it frees. If you need to turn the flag off for a chunk that was freed by your application instead of by libpng, you can use png_set_invalid(png_ptr, info_ptr, mask); + mask - identifies the chunks to be made invalid, containing the bitwise OR of one or more of @@ -2227,21 +2809,24 @@ png_infop info_ptr; png_ptr = png_create_read_struct (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, user_error_fn, user_warning_fn); + if (!png_ptr) return (ERROR); + info_ptr = png_create_info_struct(png_ptr); + if (!info_ptr) { - png_destroy_read_struct(&png_ptr, (png_infopp)NULL, - (png_infopp)NULL); - return (ERROR); + png_destroy_read_struct(&png_ptr, + (png_infopp)NULL, (png_infopp)NULL); + return (ERROR); } if (setjmp(png_jmpbuf(png_ptr))) { - png_destroy_read_struct(&png_ptr, &info_ptr, - (png_infopp)NULL); - return (ERROR); + png_destroy_read_struct(&png_ptr, &info_ptr, + (png_infopp)NULL); + return (ERROR); } /* This one's new. You can provide functions @@ -2273,9 +2858,9 @@ png_infop info_ptr; { if (setjmp(png_jmpbuf(png_ptr))) { - png_destroy_read_struct(&png_ptr, &info_ptr, + png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); - return (ERROR); + return (ERROR); } /* This one's new also. Simply give it a chunk @@ -2292,6 +2877,12 @@ png_infop info_ptr; so there. */ png_process_data(png_ptr, info_ptr, buffer, length); + + /* At this point you can call png_process_data_skip if + you want to handle data the library will skip yourself; + it simply returns the number of bytes to skip (and stops + libpng skipping that number of bytes on the next + png_process_data call). return 0; } @@ -2312,6 +2903,19 @@ png_infop info_ptr; any). You may start getting rows before png_process_data() returns, so this is your last chance to prepare for that. + + This is where you turn on interlace handling, + assuming you don't want to do it yourself. + + If you need to you can stop the processing of + your original input data at this point by calling + png_process_data_pause. This returns the number + of unprocessed bytes from the last png_process_data + call - it is up to you to ensure that the next call + sees these bytes again. If you don't want to bother + with this you can get libpng to cache the unread + bytes by setting the 'save' parameter (see png.h) but + then libpng will have to copy the data internally. */ } @@ -2332,14 +2936,22 @@ png_infop info_ptr; supplying them because it may make your life easier. - For the non-NULL rows of interlaced images, + If you did not turn on interlace handling then + the callback is called for each row of each + sub-image when the image is interlaced. In this + case 'row_num' is the row in the sub-image, not + the row in the output image as it is in all other + cases. + + For the non-NULL rows of interlaced images when + you have switched on libpng interlace handling, you must call png_progressive_combine_row() passing in the row and the old row. You can call this function for NULL rows (it will just return) and for non-interlaced images (it just does the memcpy for you) if it will make the code easier. Thus, you can just do this for - all cases: + all cases if you switch on interlace handling; */ png_progressive_combine_row(png_ptr, old_row, @@ -2353,6 +2965,9 @@ png_infop info_ptr; for interlaced images), you will have to pass the current row, and the function will combine the old row and the new row. + + You can also call png_process_data_pause in this + callback - see above. */ } @@ -2387,10 +3002,9 @@ using the standard I/O functions, you will need to replace them with custom writing functions. See the discussion under Customizing libpng. FILE *fp = fopen(file_name, "wb"); + if (!fp) - { return (ERROR); - } Next, png_struct and png_info need to be allocated and initialized. As these can be both relatively large, you may not want to store these @@ -2403,6 +3017,7 @@ both "png_ptr"; you can call them anything you like, such as png_structp png_ptr = png_create_write_struct (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, user_error_fn, user_warning_fn); + if (!png_ptr) return (ERROR); @@ -2410,7 +3025,7 @@ both "png_ptr"; you can call them anything you like, such as if (!info_ptr) { png_destroy_write_struct(&png_ptr, - (png_infopp)NULL); + (png_infopp)NULL); return (ERROR); } @@ -2436,7 +3051,7 @@ section below for more information on the libpng error handling. if (setjmp(png_jmpbuf(png_ptr))) { - png_destroy_write_struct(&png_ptr, &info_ptr); + png_destroy_write_struct(&png_ptr, &info_ptr); fclose(fp); return (ERROR); } @@ -2444,9 +3059,13 @@ section below for more information on the libpng error handling. return; If you would rather avoid the complexity of setjmp/longjmp issues, -you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case +you can compile libpng with PNG_NO_SETJMP, in which case errors will result in a call to PNG_ABORT() which defaults to abort(). +You can #define PNG_ABORT() to a function that does something +more useful than abort(), as long as your function does not +return. + Now you need to set up the output code. The default for libpng is to use the C function fwrite(). If you use this, you will need to pass a valid FILE * in the function png_init_io(). Be sure that the file is @@ -2471,7 +3090,7 @@ called after each row has been written, which you can use to control a progress meter or the like. It's demonstrated in pngtest.c. You must supply a function - void write_row_callback(png_ptr, png_uint_32 row, + void write_row_callback(png_structp png_ptr, png_uint_32 row, int pass); { /* put your code here */ @@ -2502,7 +3121,8 @@ filter types. /* turn on or off filtering, and/or choose specific filters. You can use either a single PNG_FILTER_VALUE_NAME or the bitwise OR of one - or more PNG_FILTER_NAME masks. */ + or more PNG_FILTER_NAME masks. + */ png_set_filter(png_ptr, 0, PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE | PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB | @@ -2511,11 +3131,10 @@ filter types. PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH| PNG_ALL_FILTERS); -If an application -wants to start and stop using particular filters during compression, -it should start out with all of the filters (to ensure that the previous -row of pixels will be stored in case it's needed later), and then add -and remove them after the start of compression. +If an application wants to start and stop using particular filters during +compression, it should start out with all of the filters (to ensure that +the previous row of pixels will be stored in case it's needed later), +and then add and remove them after the start of compression. If you are writing a PNG datastream that is to be embedded in a MNG datastream, the second parameter can be either 0 or 64. @@ -2559,16 +3178,20 @@ Some of the more important parts of the png_info are: png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, color_type, interlace_type, compression_type, filter_method) + width - holds the width of the image in pixels (up to 2^31). + height - holds the height of the image in pixels (up to 2^31). + bit_depth - holds the bit depth of one of the image channels. (valid values are 1, 2, 4, 8, 16 and depend also on the color_type. See also significant bits (sBIT) below). + color_type - describes which color/alpha channels are present. PNG_COLOR_TYPE_GRAY @@ -2588,8 +3211,10 @@ Some of the more important parts of the png_info are: interlace_type - PNG_INTERLACE_NONE or PNG_INTERLACE_ADAM7 + compression_type - (must be PNG_COMPRESSION_TYPE_DEFAULT) + filter_method - (must be PNG_FILTER_TYPE_DEFAULT or, if you are writing a PNG to be embedded in a MNG datastream, @@ -2607,15 +3232,22 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_PLTE(png_ptr, info_ptr, palette, num_palette); + palette - the palette for the file (array of png_color) num_palette - number of entries in the palette - png_set_gAMA(png_ptr, info_ptr, gamma); - gamma - the gamma the image was created - at (PNG_INFO_gAMA) + png_set_gAMA(png_ptr, info_ptr, file_gamma); + png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma); + + file_gamma - the gamma at which the image was + created (PNG_INFO_gAMA) + + int_file_gamma - 100,000 times the gamma at which + the image was created png_set_sRGB(png_ptr, info_ptr, srgb_intent); + srgb_intent - the rendering intent (PNG_INFO_sRGB) The presence of the sRGB chunk means that the pixel @@ -2635,6 +3267,7 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, srgb_intent); + srgb_intent - the rendering intent (PNG_INFO_sRGB) The presence of the sRGB chunk means that the pixel @@ -2645,17 +3278,22 @@ width, height, bit_depth, and color_type must be the same in each call. written. png_set_iCCP(png_ptr, info_ptr, name, compression_type, - profile, proflen); - name - The profile name. - compression - The compression type; always - PNG_COMPRESSION_TYPE_BASE for PNG 1.0. - You may give NULL to this argument to - ignore it. - profile - International Color Consortium color - profile data. May contain NULs. - proflen - length of profile data in bytes. + profile, proflen); + + name - The profile name. + + compression_type - The compression type; always + PNG_COMPRESSION_TYPE_BASE for PNG 1.0. + You may give NULL to this argument to + ignore it. + + profile - International Color Consortium color + profile data. May contain NULs. + + proflen - length of profile data in bytes. png_set_sBIT(png_ptr, info_ptr, sig_bit); + sig_bit - the number of significant bits for (PNG_INFO_sBIT) each of the gray, red, green, and blue channels, whichever are @@ -2664,30 +3302,37 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_tRNS(png_ptr, info_ptr, trans_alpha, num_trans, trans_color); + trans_alpha - array of alpha (transparency) entries for palette (PNG_INFO_tRNS) + trans_color - graylevel or color sample values (in order red, green, blue) of the single transparent color for non-paletted images (PNG_INFO_tRNS) + num_trans - number of transparent entries (PNG_INFO_tRNS) png_set_hIST(png_ptr, info_ptr, hist); - (PNG_INFO_hIST) + hist - histogram of palette (array of - png_uint_16) + png_uint_16) (PNG_INFO_hIST) png_set_tIME(png_ptr, info_ptr, mod_time); + mod_time - time image was last modified (PNG_VALID_tIME) png_set_bKGD(png_ptr, info_ptr, background); + background - background color (PNG_VALID_bKGD) png_set_text(png_ptr, info_ptr, text_ptr, num_text); + text_ptr - array of png_text holding image comments + text_ptr[i].compression - type of compression used on "text" PNG_TEXT_COMPRESSION_NONE PNG_TEXT_COMPRESSION_zTXt @@ -2713,6 +3358,7 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_sPLT(png_ptr, info_ptr, &palette_ptr, num_spalettes); + palette_ptr - array of png_sPLT_struct structures to be added to the list of palettes in the info structure. @@ -2721,35 +3367,48 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, unit_type); + offset_x - positive offset from the left edge of the screen + offset_y - positive offset from the top edge of the screen + unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER png_set_pHYs(png_ptr, info_ptr, res_x, res_y, unit_type); + res_x - pixels/unit physical resolution in x direction + res_y - pixels/unit physical resolution in y direction + unit_type - PNG_RESOLUTION_UNKNOWN, PNG_RESOLUTION_METER png_set_sCAL(png_ptr, info_ptr, unit, width, height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units (width and height are doubles) png_set_sCAL_s(png_ptr, info_ptr, unit, width, height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units (width and height are strings like "2.54") png_set_unknown_chunks(png_ptr, info_ptr, &unknowns, num_unknowns) + unknowns - array of png_unknown_chunk structures holding unknown chunks unknowns[i].name - name of unknown chunk @@ -2788,21 +3447,30 @@ Until text gets around 1000 bytes, it is not worth compressing it. After the text has been written out to the file, the compression type is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR, so that it isn't written out again at the end (in case you are calling -png_write_end() with the same struct. +png_write_end() with the same struct). The keywords that are given in the PNG Specification are: Title Short (one line) title or caption for image + Author Name of image's creator + Description Description of image (possibly long) + Copyright Copyright notice + Creation Time Time of original image creation (usually RFC 1123 format, see below) + Software Software used to create the image + Disclaimer Legal disclaimer + Warning Warning of nature of content + Source Device used to create the image + Comment Miscellaneous comment; conversion from other image format @@ -2972,17 +3640,19 @@ file so that decoders can recover the original data if desired. /* Set the true bit depth of the image data */ if (color_type & PNG_COLOR_MASK_COLOR) { - sig_bit.red = true_bit_depth; - sig_bit.green = true_bit_depth; - sig_bit.blue = true_bit_depth; + sig_bit.red = true_bit_depth; + sig_bit.green = true_bit_depth; + sig_bit.blue = true_bit_depth; } + else { - sig_bit.gray = true_bit_depth; + sig_bit.gray = true_bit_depth; } + if (color_type & PNG_COLOR_MASK_ALPHA) { - sig_bit.alpha = true_bit_depth; + sig_bit.alpha = true_bit_depth; } png_set_sBIT(png_ptr, info_ptr, &sig_bit); @@ -3028,11 +3698,18 @@ with You must supply the function - void write_transform_fn(png_ptr ptr, row_info_ptr - row_info, png_bytep data) + void write_transform_fn(png_structp png_ptr ptr, + row_info_ptr row_info, png_bytep data) See pngtest.c for a working example. Your function will be called -before any of the other transformations are processed. +before any of the other transformations are processed. If supported +libpng also supplies an information routine that may be called from +your callback: + + png_get_current_row_number(png_ptr); + +This returns the current row passed to the transform. Even with interlaced +images the value returned is the row in the final output image. You can also set up a pointer to a user structure for use by your callback function. @@ -3114,25 +3791,39 @@ for details of which pixels to write when. If you don't want libpng to handle the interlacing details, just use png_set_interlace_handling() and call png_write_rows() the -correct number of times to write all seven sub-images. +correct number of times to write all the sub-images +(png_set_interlace_handling() returns the number of sub-images.) If you want libpng to build the sub-images, call this before you start writing any rows: - number_of_passes = - png_set_interlace_handling(png_ptr); + number_of_passes = png_set_interlace_handling(png_ptr); This will return the number of passes needed. Currently, this is seven, but may change if another interlace type is added. Then write the complete image number_of_passes times. - png_write_rows(png_ptr, row_pointers, - number_of_rows); + png_write_rows(png_ptr, row_pointers, number_of_rows); + +Think carefully before you write an interlaced image. Typically code that +reads such images reads all the image data into memory, uncompressed, before +doing any processing. Only code that can display an image on the fly can +take advantage of the interlacing and even then the image has to be exactly +the correct size for the output device, because scaling an image requires +adjacent pixels and these are not available until all the passes have been +read. + +If you do write an interlaced image you will hardly ever need to handle +the interlacing yourself. Call png_set_interlace_handling() and use the +approach described above. -As some of these rows are not used, and thus return immediately, you may -want to read about interlacing in the PNG specification, and only update -the rows that are actually used. +The only time it is conceivable that you will really need to write an +interlaced image pass-by-pass is when you have read one pass by pass and +made some pixel-by-pixel transformation to it, as described in the read +code above. In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros +to determine the size of each sub-image in turn and simply write the rows +you obtained from the read code. .SS Finishing a sequential write @@ -3151,6 +3842,7 @@ It is also possible to individually free the info_ptr members that point to libpng-allocated storage with the following function: png_free_data(png_ptr, info_ptr, mask, seq) + mask - identifies data to be freed, a mask containing the bitwise OR of one or more of @@ -3160,6 +3852,7 @@ point to libpng-allocated storage with the following function: PNG_FREE_SCAL, PNG_FREE_SPLT, PNG_FREE_TEXT, PNG_FREE_UNKN, or simply PNG_FREE_ALL + seq - sequence number of item to be freed (-1 for all items) @@ -3181,19 +3874,22 @@ or so that it will free data that was allocated by the user with png_malloc() or png_zalloc() and passed in via a png_set_*() function, with png_data_freer(png_ptr, info_ptr, freer, mask) - mask - which data elements are affected - same choices as in png_free_data() + freer - one of PNG_DESTROY_WILL_FREE_DATA PNG_SET_WILL_FREE_DATA PNG_USER_WILL_FREE_DATA + mask - which data elements are affected + same choices as in png_free_data() + For example, to transfer responsibility for some data from a read structure to a write structure, you could use png_data_freer(read_ptr, read_info_ptr, PNG_USER_WILL_FREE_DATA, PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) + png_data_freer(write_ptr, write_info_ptr, PNG_DESTROY_WILL_FREE_DATA, PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) @@ -3240,9 +3936,11 @@ these functions, call the appropriate png_set_*_fn() function. Memory allocation is done through the functions png_malloc(), png_calloc(), and png_free(). These currently just call the standard C functions. -png_calloc() calls png_malloc() and then png_memset() to clear the newly -allocated memory to zero. If your pointers can't access more then 64K -at a time, you will want to set MAXSEG_64K in zlib.h. Since it is +png_calloc() calls png_malloc() and then clears the newly +allocated memory to zero. There is limited support for certain systems +with segmented memory architectures and the types of pointers declared by +png.h match this; you will have to use appropriate pointers in your +application. Since it is unlikely that the method of handling memory allocation on a platform will change between applications, these functions must be modified in the library at compile time. If you prefer to use a different method @@ -3256,7 +3954,8 @@ via Your replacement memory functions must have prototypes as follows: png_voidp malloc_fn(png_structp png_ptr, - png_size_t size); + png_alloc_size_t size); + void free_fn(png_structp png_ptr, png_voidp ptr); Your malloc_fn() must return NULL in case of failure. The png_malloc() @@ -3289,8 +3988,10 @@ The replacement I/O functions must have prototypes as follows: void user_read_data(png_structp png_ptr, png_bytep data, png_size_t length); + void user_write_data(png_structp png_ptr, png_bytep data, png_size_t length); + void user_flush_data(png_structp png_ptr); The user_read_data() function is responsible for detecting and @@ -3307,8 +4008,9 @@ Error handling in libpng is done through png_error() and png_warning(). Errors handled through png_error() are fatal, meaning that png_error() should never return to its caller. Currently, this is handled via setjmp() and longjmp() (unless you have compiled libpng with -PNG_SETJMP_NOT_SUPPORTED, in which case it is handled via PNG_ABORT()), -but you could change this to do things like exit() if you should wish. +PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()), +but you could change this to do things like exit() if you should wish, +as long as your function does not return. On non-fatal errors, png_warning() is called to print a warning message, and then control returns to the calling code. @@ -3334,6 +4036,7 @@ parameters as follows: void user_error_fn(png_structp png_ptr, png_const_charp error_msg); + void user_warning_fn(png_structp png_ptr, png_const_charp warning_msg); @@ -3444,8 +4147,10 @@ zlib.h for more information on what these mean. png_set_compression_strategy(png_ptr, strategy); + png_set_compression_window_bits(png_ptr, window_bits); + png_set_compression_method(png_ptr, method); png_set_compression_buffer_size(png_ptr, size); @@ -3535,6 +4240,8 @@ before recompiling libpng and save yourself code and data space, or you can turn off individual capabilities with defines that begin with PNG_NO_. +In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead. + You can also turn all of the transforms and ancillary chunk capabilities off en masse with compiler directives that define PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS, @@ -3587,8 +4294,8 @@ according to printf-style formatting directives. For example, is expanded to - if(PNG_DEBUG > 2) - fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo); + if (PNG_DEBUG > 2) + fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo); When PNG_DEBUG is defined but is zero, the macros aren't defined, but you can still use PNG_DEBUG to control your own debugging: @@ -3609,11 +4316,13 @@ Libpng can support some of these extensions. To enable them, use the png_permit_mng_features() function: feature_set = png_permit_mng_features(png_ptr, mask) + mask is a png_uint_32 containing the bitwise OR of the features you want to enable. These include PNG_FLAG_MNG_EMPTY_PLTE PNG_FLAG_MNG_FILTER_64 PNG_ALL_MNG_FEATURES + feature_set is a png_uint_32 that is the bitwise AND of your mask with the set of MNG features that is supported by the version of libpng that you are using. @@ -3638,7 +4347,7 @@ still alive and well, but they have moved on to other things. The old libpng functions png_read_init(), png_write_init(), png_info_init(), png_read_destroy(), and png_write_destroy() have been moved to PNG_INTERNAL in version 0.95 to discourage their use. These -functions will be removed from libpng version 2.0.0. +functions will be removed from libpng version 1.4.0. The preferred method of creating and initializing the libpng structures is via the png_create_read_struct(), png_create_write_struct(), and @@ -3827,21 +4536,29 @@ png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(), png_set_asm_flags(), and png_mmx_supported() We removed the obsolete png_check_sig(), png_memcpy_check(), and -png_memset_check() functions. Instead use !png_sig_cmp(), png_memcpy(), -and png_memset(), respectively. +png_memset_check() functions. Instead use !png_sig_cmp(), memcpy(), +and memset(), respectively. The function png_set_gray_1_2_4_to_8() was removed. It has been deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with png_set_expand_gray_1_2_4_to_8() because the former function also expanded palette images. +Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32 +were added and are used by default instead of the corresponding +functions. Unfortunately, +from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the +function) incorrectly returned a value of type png_uint_32. + We changed the prototype for png_malloc() from png_malloc(png_structp png_ptr, png_uint_32 size) to png_malloc(png_structp png_ptr, png_alloc_size_t size) +This also applies to the prototype for the user replacement malloc_fn(). + The png_calloc() function was added and is used in place of -of "png_malloc(); png_memset();" except in the case in png_read_png() +of "png_malloc(); memset();" except in the case in png_read_png() where the array consists of pointers; in this case a "for" loop is used after the png_malloc() to set the pointers to NULL, to give robust. behavior in case the application runs out of memory part-way through @@ -3859,9 +4576,287 @@ The png_zalloc() and png_zfree() functions are no longer exported. The png_zalloc() function no longer zeroes out the memory that it allocates. +Support for dithering was disabled by default in libpng-1.4.0, because +been well tested and doesn't actually "dither". The code was not +removed, however, and could be enabled by building libpng with +PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support +was reenabled, but the function was renamed png_set_quantize() to +reflect more accurately what it actually does. At the same time, +the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to +PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED +was renamed to PNG_READ_QUANTIZE_SUPPORTED. + We removed the trailing '.' from the warning and error messages. -.SH X. Detecting libpng +.SH X. Changes to Libpng from version 1.4.x to 1.5.x + +From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the +function) incorrectly returned a value of type png_uint_32. + +A. Changes that affect users of libpng + +There are no substantial API changes between the non-deprecated parts of +the 1.4.5 API and the 1.5.0 API, however the ability to directly access +the main libpng control structures, png_struct and png_info, deprecated +in earlier versions of libpng, has been completely removed from +libpng 1.5. + +We no longer include zlib.h in png.h. Applications that need access +to information in zlib.h will need to add the '#include "zlib.h"' +directive. It does not matter whether it is placed prior to or after +the '"#include png.h"' directive. + +We moved the png_strcpy(), png_strncpy(), png_strlen(), png_memcpy(), +png_memcmp(), png_sprintf, and png_memcpy() macros into a private +header file (pngpriv.h) that is not accessible to applications. + +In png_get_iCCP, the type of "profile" was changed from png_charpp +to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep. + +There are changes of form in png.h, including new and changed macros to +declare +parts of the API. Some API functions with arguments that are pointers to +data not modified within the function have been corrected to declare +these arguments with PNG_CONST. + +Much of the internal use of C macros to control the library build has also +changed and some of this is visible in the exported header files, in +particular the use of macros to control data and API elements visible +during application compilation may require significant revision to +application code. (It is extremely rare for an application to do this.) + +Any program that compiled against libpng 1.4 and did not use deprecated +features or access internal library structures should compile and work +against libpng 1.5. + +libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of +interlaced images. The macros return the number of rows and columns in +each pass and information that can be used to de-interlace and (if +absolutely necessary) interlace an image. + +libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls +the application provided png_longjmp_ptr on the internal, but application +initialized, jmpbuf. It is provided as a convenience to avoid the need +to use the png_jmpbuf macro, which had the unnecessary side effect of +resetting the internal png_longjmp_ptr value. + +libpng 1.5.0 includes a complete fixed point API. By default this is +present along with the corresponding floating point API. In general the +fixed point API is faster and smaller than the floating point one because +the PNG file format used fixed point, not floating point. This applies +even if the library uses floating point in internal calculations. A new +macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library +uses floating point arithmetic (the default) or fixed point arithmetic +internally for performance critical calculations such as gamma correction. +In some cases, the gamma calculations may produce slightly different +results. This has changed the results in png_rgb_to_gray and in alpha +composition (png_set_background for example). This applies even if the +original image was already linear (gamma == 1.0) and, therefore, it is +not necessary to linearize the image. This is because libpng has *not* +been changed to optimize that case correctly, yet. + +Fixed point support for the sCAL chunk comes with an important caveat; +the sCAL specification uses a decimal encoding of floating point values +and the accuracy of PNG fixed point values is insufficient for +representation of these values. Consequently a "string" API +(png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading +arbitrary sCAL chunks in the absence of either the floating point API or +internal floating point calculations. + +Applications no longer need to include the optional distribution header +file pngusr.h or define the corresponding macros during application +build in order to see the correct variant of the libpng API. From 1.5.0 +application code can check for the corresponding _SUPPORTED macro: + +#ifdef PNG_INCH_CONVERSIONS_SUPPORTED + /* code that uses the inch conversion APIs. */ +#endif + +This macro will only be defined if the inch conversion functions have been +compiled into libpng. The full set of macros, and whether or not support +has been compiled in, are available in the header file pnglibconf.h. +This header file is specific to the libpng build. Notice that prior to +1.5.0 the _SUPPORTED macros would always have the default definition unless +reset by pngusr.h or by explicit settings on the compiler command line. +These settings may produce compiler warnings or errors in 1.5.0 because +of macro redefinition. + +From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the +function) incorrectly returned a value of type png_uint_32. libpng 1.5.0 +is consistent with the implementation in 1.4.5 and 1.2.x (where the macro +did not exist.) + +Applications can now choose whether to use these macros or to call the +corresponding function by defining PNG_USE_READ_MACROS or +PNG_NO_USE_READ_MACROS before including png.h. Notice that this is +only supported from 1.5.0 -defining PNG_NO_USE_READ_MACROS prior to 1.5.0 + will lead to a link failure. + +B. Changes to the build and configuration of libpng + +Details of internal changes to the library code can be found in the CHANGES +file. These will be of no concern to the vast majority of library users or +builders, however the few who configure libpng to a non-default feature +set may need to change how this is done. + +There should be no need for library builders to alter build scripts if +these use the distributed build support - configure or the makefiles - +however users of the makefiles may care to update their build scripts +to build pnglibconf.h where the corresponding makefile does not do so. + +Building libpng with a non-default configuration has changed completely. +The old method using pngusr.h should still work correctly even though the +way pngusr.h is used in the build has been changed, however library +builders will probably want to examine the changes to take advantage of +new capabilities and to simplify their build system. + +B.1 Specific changes to library configuration capabilities + +The library now supports a complete fixed point implementation and can +thus be used on systems which have no floating point support or very +limited or slow support. Previously gamma correction, an essential part +of complete PNG support, required reasonably fast floating point. + +As part of this the choice of internal implementation has been made +independent of the choice of fixed versus floating point APIs and all the +missing fixed point APIs have been implemented. + +The exact mechanism used to control attributes of API functions has +changed. A single set of operating system independent macro definitions +is used and operating system specific directives are defined in +pnglibconf.h + +As part of this the mechanism used to choose procedure call standards on +those systems that allow a choice has been changed. At present this only +affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems +running on Intel processors. As before PNGAPI is defined where required +to control the exported API functions; however, two new macros, PNGCBAPI +and PNGCAPI, are used instead for callback functions (PNGCBAPI) and +(PNGCAPI) for functions that must match a C library prototype (currently +only png_longjmp_ptr, which must match the C longjmp function.) The new +approach is documented in pngconf.h + +Despite these changes libpng 1.5.0 only supports the native C function +calling standard on those platforms tested so far (__cdecl on Microsoft +Windows). This is because the support requirements for alternative +calling conventions seem to no longer exist. Developers who find it +necessary to set PNG_API_RULE to 1 should advise the mailing list +(png-mng-implement) of this and library builders who use Openwatcom and +therefore set PNG_API_RULE to 2 should also contact the mailing list. + +A new test program, pngvalid, is provided in addition to pngtest. +pngvalid validates the arithmetic accuracy of the gamma correction +calculations and includes a number of validations of the file format. +A subset of the full range of tests is run when "make check" is done +(in the 'configure' build.) pngvalid also allows total allocated memory +usage to be evaluated and performs additional memory overwrite validation. + +Many changes to individual feature macros have been made. The following +are the changes most likely to be noticed by library builders who +configure libpng: + +1) All feature macros now have consistent naming: + +#define PNG_NO_feature turns the feature off +#define PNG_feature_SUPPORTED turns the feature on + +pnglibconf.h contains one line for each feature macro which is either: + +#define PNG_feature_SUPPORTED + +if the feature is supported or: + +/*#undef PNG_feature_SUPPORTED*/ + +if it is not. Library code consistently checks for the 'SUPPORTED' macro. +It does not, and should not, check for the 'NO' macro which will not +normally be defined even if the feature is not supported. + +Compatibility with the old names is provided as follows: + +PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED + +And the following definitions disable the corresponding feature: + +PNG_SETJMP_NOT_SUPPORTED disables SETJMP +PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS +PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV +PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS +PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS +PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS + +Library builders should remove use of the above, inconsistent, names. + +2) Warning and error message formatting was previously conditional on +the STDIO feature. The library has been changed to use the +CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled +the library no longer uses the printf(3) functions, even though the +default read/write implementations use (FILE) style stdio.h functions. + +3) Three feature macros now control the fixed/floating point decisions: + +PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs + +PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in +practice these are normally required internally anyway (because the PNG +file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT +merely stops the function from being exported. + +PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating +point implementation or the fixed point one. Typically the fixed point +implementation is larger and slower than the floating point implementation +on a system that supports floating point, however it may be faster on a +system which lacks floating point hardware and therefore uses a software +emulation. + +4) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the +functions to read and write ints to be disabled independently of +PNG_USE_READ_MACROS, which allows libpng to be built with the functions +even though the default is to use the macros - this allows applications +to choose at app buildtime whether or not to use macros (previously +impossible because the functions weren't in the default build.) + +B.2 Changes to the configuration mechanism + +Prior to libpng-1.5.0 library builders who needed to configure libpng +had either to modify the exported pngconf.h header file to add system +specific configuration or had to write feature selection macros into +pngusr.h and cause this to be included into pngconf.h by defining +PNG_USER_CONFIG. The latter mechanism had the disadvantage that an +application built without PNG_USER_CONFIG defined would see the +unmodified, default, libpng API and thus would probably fail to link. + +These mechanisms still work in the configure build and in any makefile +build that builds pnglibconf.h although the feature selection macros +have changed somewhat as described above. In 1.5.0, however, pngusr.h is +processed only once, when the exported header file pnglibconf.h is built. +pngconf.h no longer includes pngusr.h, therefore it is ignored after the +build of pnglibconf.h and it is never included in an application build. + +The rarely used alternative of adding a list of feature macros to the +CFLAGS setting in the build also still works, however the macros will be +copied to pnglibconf.h and this may produce macro redefinition warnings +when the individual C files are compiled. + +All configuration now only works if pnglibconf.h is built from +scripts/pnglibconf.dfa. This requires the program awk. Brian Kernighan +(the original author of awk) maintains C source code of that awk and this +and all known later implementations (often called by subtly different +names - nawk and gawk for example) are adequate to build pnglibconf.h. +The Sun Microsystems (now Oracle) program 'awk' is an earlier version +and does not work, this may also apply to other systems that have a +functioning awk called 'nawk'. + +Configuration options are now documented in scripts/pnglibconf.dfa. This +file also includes dependency information that ensures a configuration is +consistent; that is, if a feature is switched off dependent features are +also removed. As a recommended alternative to using feature macros in +pngusr.h a system builder may also define equivalent options in pngusr.dfa +(or, indeed, any file) and add that to the configuration by setting +DFA_XTRA to the file name. The makefiles in contrib/pngminim illustrate +how to do this, and a case where pngusr.h is still required. + +.SH XI. Detecting libpng The png_get_io_ptr() function has been present since libpng-0.88, has never changed, and is unaffected by conditional compilation macros. It is the @@ -3870,7 +4865,7 @@ libpng version since 0.88. In an autoconf "configure.in" you could use AC_CHECK_LIB(png, png_get_io_ptr, ... -.SH XI. Source code repository +.SH XII. Source code repository Since about February 2009, version 1.2.34, libpng has been under "git" source control. The git repository was built from old libpng-x.y.z.tar.gz files @@ -3889,7 +4884,12 @@ the libpng bug tracker at http://libpng.sourceforge.net -.SH XII. Coding style +We also accept patches built from the tar or zip distributions, and +simple verbal discriptions of bug fixes, reported either to the +SourceForge bug tracker or to the png-mng-implement at lists.sf.net +mailing list. + +.SH XIII. Coding style Our coding style is similar to the "Allman" style, with curly braces on separate lines: @@ -3928,12 +4928,12 @@ the statement that follows the comment: /* Single-line comment */ statement; - /* Multiple-line - * comment + /* This is a multiple-line + * comment. */ statement; -Very short comments can be placed at the end of the statement +Very short comments can be placed after the end of the statement to which they pertain: statement; /* comment */ @@ -3946,7 +4946,7 @@ Functions and their curly braces are not indented, and exported functions are marked with PNGAPI: /* This is a public function that is visible to - * application programers. It does thus-and-so. + * application programmers. It does thus-and-so. */ void PNGAPI png_exported_function(png_ptr, png_info, foo) @@ -3974,15 +4974,16 @@ above the comment that says /* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */ -The names of all exported functions and variables begin -with "png_", and all publicly visible C preprocessor -macros begin with "PNG_". +To avoid polluting the global namespace, the names of all exported +functions and variables begin with "png_", and all publicly visible C +preprocessor macros begin with "PNG_". We request that applications that +use libpng *not* begin any of their own symbols with either of these strings. We put a space after each comma and after each semicolon -in "for" statments, and we put spaces before and after each -C binary operator and after "for" or "while". We don't -put a space between a typecast and the expression being -cast, nor do we put one between a function name and the +in "for" statements, and we put spaces before and after each +C binary operator and after "for" or "while", and before +"?". We don't put a space between a typecast and the expression +being cast, nor do we put one between a function name and the left parenthesis that follows it: for (i = 2; i > 0; --i) @@ -3997,15 +4998,15 @@ Lines do not exceed 80 characters. Other rules can be inferred by inspecting the libpng source. -.SH XIII. Y2K Compliance in libpng +.SH XIV. Y2K Compliance in libpng -January 3, 2010 +February 3, 2011 Since the PNG Development group is an ad-hoc body, we can't make an official declaration. This is your unofficial assurance that libpng from version 0.71 and -upward through 1.4.0 are Y2K compliant. It is my belief that earlier +upward through 1.5.1 are Y2K compliant. It is my belief that earlier versions were also Y2K compliant. Libpng only has three year fields. One is a 2-byte unsigned integer that @@ -4178,6 +5179,19 @@ the first widely used release: 1.4.0beta88-109 14 10400 14.so.14.0[.0] 1.4.0rc02-08 14 10400 14.so.14.0[.0] 1.4.0 14 10400 14.so.14.0[.0] + 1.4.1beta01-03 14 10401 14.so.14.1[.0] + 1.4.1rc01 14 10401 14.so.14.1[.0] + 1.4.1beta04-12 14 10401 14.so.14.1[.0] + 1.4.1 14 10401 14.so.14.1[.0] + 1.4.2 14 10402 14.so.14.2[.0] + 1.4.3 14 10403 14.so.14.3[.0] + 1.4.4 14 10404 14.so.14.4[.0] + 1.5.0beta01-58 15 10500 15.so.15.0[.0] + 1.5.0rc01-07 15 10500 15.so.15.0[.0] + 1.5.0 15 10500 15.so.15.0[.0] + 1.5.1beta01-11 15 10501 15.so.15.1[.0] + 1.5.1rc01-02 15 10501 15.so.15.1[.0] + 1.5.1 15 10501 15.so.15.1[.0] Henceforth the source version will match the shared-library minor and patch numbers; the shared-library major version number will be @@ -4190,7 +5204,8 @@ version 1.0.6j; from then on they were given the upcoming public release number plus "betaNN" or "rcN". .SH "SEE ALSO" -libpngpf(3), png(5) +.BR "png"(5), " libpngpf"(3), " zlib"(3), " deflate"(5), " " and " zlib"(5) + .LP .IR libpng : .IP @@ -4233,7 +5248,7 @@ possible without all of you. Thanks to Frank J. T. Wojcik for helping with the documentation. -Libpng version 1.4.0 - January 3, 2010: +Libpng version 1.5.1 - February 3, 2011: Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc. Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net). @@ -4256,7 +5271,7 @@ this sentence. This code is released under the libpng license. -libpng versions 1.2.6, August 15, 2004, through 1.4.0, January 3, 2010, are +libpng versions 1.2.6, August 15, 2004, through 1.5.1, February 3, 2011, are Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are distributed according to the same disclaimer and license as libpng-1.2.5 with the following individual added to the list of Contributing Authors @@ -4355,7 +5370,7 @@ certification mark of the Open Source Initiative. Glenn Randers-Pehrson glennrp at users.sourceforge.net -January 3, 2010 +February 3, 2011 .\" end of man page |