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Diffstat (limited to 'src/3rdparty/libpng/png.c')
| -rw-r--r-- | src/3rdparty/libpng/png.c | 2362 |
1 files changed, 2362 insertions, 0 deletions
diff --git a/src/3rdparty/libpng/png.c b/src/3rdparty/libpng/png.c new file mode 100644 index 0000000000..764f47c20c --- /dev/null +++ b/src/3rdparty/libpng/png.c @@ -0,0 +1,2362 @@ + +/* png.c - location for general purpose libpng functions + * + * Last changed in libpng 1.5.1 [February 3, 2011] + * Copyright (c) 1998-2011 Glenn Randers-Pehrson + * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) + * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) + * + * This code is released under the libpng license. + * For conditions of distribution and use, see the disclaimer + * and license in png.h + */ + +#include "pngpriv.h" + +/* Generate a compiler error if there is an old png.h in the search path. */ +typedef png_libpng_version_1_5_1 Your_png_h_is_not_version_1_5_1; + +/* Tells libpng that we have already handled the first "num_bytes" bytes + * of the PNG file signature. If the PNG data is embedded into another + * stream we can set num_bytes = 8 so that libpng will not attempt to read + * or write any of the magic bytes before it starts on the IHDR. + */ + +#ifdef PNG_READ_SUPPORTED +void PNGAPI +png_set_sig_bytes(png_structp png_ptr, int num_bytes) +{ + png_debug(1, "in png_set_sig_bytes"); + + if (png_ptr == NULL) + return; + + if (num_bytes > 8) + png_error(png_ptr, "Too many bytes for PNG signature"); + + png_ptr->sig_bytes = (png_byte)(num_bytes < 0 ? 0 : num_bytes); +} + +/* Checks whether the supplied bytes match the PNG signature. We allow + * checking less than the full 8-byte signature so that those apps that + * already read the first few bytes of a file to determine the file type + * can simply check the remaining bytes for extra assurance. Returns + * an integer less than, equal to, or greater than zero if sig is found, + * respectively, to be less than, to match, or be greater than the correct + * PNG signature (this is the same behaviour as strcmp, memcmp, etc). + */ +int PNGAPI +png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check) +{ + png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10}; + + if (num_to_check > 8) + num_to_check = 8; + + else if (num_to_check < 1) + return (-1); + + if (start > 7) + return (-1); + + if (start + num_to_check > 8) + num_to_check = 8 - start; + + return ((int)(png_memcmp(&sig[start], &png_signature[start], num_to_check))); +} + +#endif /* PNG_READ_SUPPORTED */ + +#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) +/* Function to allocate memory for zlib */ +PNG_FUNCTION(voidpf /* PRIVATE */, +png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED) +{ + png_voidp ptr; + png_structp p=(png_structp)png_ptr; + png_uint_32 save_flags=p->flags; + png_alloc_size_t num_bytes; + + if (png_ptr == NULL) + return (NULL); + + if (items > PNG_UINT_32_MAX/size) + { + png_warning (p, "Potential overflow in png_zalloc()"); + return (NULL); + } + num_bytes = (png_alloc_size_t)items * size; + + p->flags|=PNG_FLAG_MALLOC_NULL_MEM_OK; + ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes); + p->flags=save_flags; + + return ((voidpf)ptr); +} + +/* Function to free memory for zlib */ +void /* PRIVATE */ +png_zfree(voidpf png_ptr, voidpf ptr) +{ + png_free((png_structp)png_ptr, (png_voidp)ptr); +} + +/* Reset the CRC variable to 32 bits of 1's. Care must be taken + * in case CRC is > 32 bits to leave the top bits 0. + */ +void /* PRIVATE */ +png_reset_crc(png_structp png_ptr) +{ + png_ptr->crc = crc32(0, Z_NULL, 0); +} + +/* Calculate the CRC over a section of data. We can only pass as + * much data to this routine as the largest single buffer size. We + * also check that this data will actually be used before going to the + * trouble of calculating it. + */ +void /* PRIVATE */ +png_calculate_crc(png_structp png_ptr, png_const_bytep ptr, png_size_t length) +{ + int need_crc = 1; + + if (png_ptr->chunk_name[0] & 0x20) /* ancillary */ + { + if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) == + (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN)) + need_crc = 0; + } + + else /* critical */ + { + if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) + need_crc = 0; + } + + if (need_crc) + png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length); +} + +/* Allocate the memory for an info_struct for the application. We don't + * really need the png_ptr, but it could potentially be useful in the + * future. This should be used in favour of malloc(png_sizeof(png_info)) + * and png_info_init() so that applications that want to use a shared + * libpng don't have to be recompiled if png_info changes size. + */ +PNG_FUNCTION(png_infop,PNGAPI +png_create_info_struct,(png_structp png_ptr),PNG_ALLOCATED) +{ + png_infop info_ptr; + + png_debug(1, "in png_create_info_struct"); + + if (png_ptr == NULL) + return (NULL); + +#ifdef PNG_USER_MEM_SUPPORTED + info_ptr = (png_infop)png_create_struct_2(PNG_STRUCT_INFO, + png_ptr->malloc_fn, png_ptr->mem_ptr); +#else + info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO); +#endif + if (info_ptr != NULL) + png_info_init_3(&info_ptr, png_sizeof(png_info)); + + return (info_ptr); +} + +/* This function frees the memory associated with a single info struct. + * Normally, one would use either png_destroy_read_struct() or + * png_destroy_write_struct() to free an info struct, but this may be + * useful for some applications. + */ +void PNGAPI +png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr) +{ + png_infop info_ptr = NULL; + + png_debug(1, "in png_destroy_info_struct"); + + if (png_ptr == NULL) + return; + + if (info_ptr_ptr != NULL) + info_ptr = *info_ptr_ptr; + + if (info_ptr != NULL) + { + png_info_destroy(png_ptr, info_ptr); + +#ifdef PNG_USER_MEM_SUPPORTED + png_destroy_struct_2((png_voidp)info_ptr, png_ptr->free_fn, + png_ptr->mem_ptr); +#else + png_destroy_struct((png_voidp)info_ptr); +#endif + *info_ptr_ptr = NULL; + } +} + +/* Initialize the info structure. This is now an internal function (0.89) + * and applications using it are urged to use png_create_info_struct() + * instead. + */ + +void PNGAPI +png_info_init_3(png_infopp ptr_ptr, png_size_t png_info_struct_size) +{ + png_infop info_ptr = *ptr_ptr; + + png_debug(1, "in png_info_init_3"); + + if (info_ptr == NULL) + return; + + if (png_sizeof(png_info) > png_info_struct_size) + { + png_destroy_struct(info_ptr); + info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO); + *ptr_ptr = info_ptr; + } + + /* Set everything to 0 */ + png_memset(info_ptr, 0, png_sizeof(png_info)); +} + +void PNGAPI +png_data_freer(png_structp png_ptr, png_infop info_ptr, + int freer, png_uint_32 mask) +{ + png_debug(1, "in png_data_freer"); + + if (png_ptr == NULL || info_ptr == NULL) + return; + + if (freer == PNG_DESTROY_WILL_FREE_DATA) + info_ptr->free_me |= mask; + + else if (freer == PNG_USER_WILL_FREE_DATA) + info_ptr->free_me &= ~mask; + + else + png_warning(png_ptr, + "Unknown freer parameter in png_data_freer"); +} + +void PNGAPI +png_free_data(png_structp png_ptr, png_infop info_ptr, png_uint_32 mask, + int num) +{ + png_debug(1, "in png_free_data"); + + if (png_ptr == NULL || info_ptr == NULL) + return; + +#ifdef PNG_TEXT_SUPPORTED + /* Free text item num or (if num == -1) all text items */ + if ((mask & PNG_FREE_TEXT) & info_ptr->free_me) + { + if (num != -1) + { + if (info_ptr->text && info_ptr->text[num].key) + { + png_free(png_ptr, info_ptr->text[num].key); + info_ptr->text[num].key = NULL; + } + } + + else + { + int i; + for (i = 0; i < info_ptr->num_text; i++) + png_free_data(png_ptr, info_ptr, PNG_FREE_TEXT, i); + png_free(png_ptr, info_ptr->text); + info_ptr->text = NULL; + info_ptr->num_text=0; + } + } +#endif + +#ifdef PNG_tRNS_SUPPORTED + /* Free any tRNS entry */ + if ((mask & PNG_FREE_TRNS) & info_ptr->free_me) + { + png_free(png_ptr, info_ptr->trans_alpha); + info_ptr->trans_alpha = NULL; + info_ptr->valid &= ~PNG_INFO_tRNS; + } +#endif + +#ifdef PNG_sCAL_SUPPORTED + /* Free any sCAL entry */ + if ((mask & PNG_FREE_SCAL) & info_ptr->free_me) + { +#if defined(PNG_FIXED_POINT_SUPPORTED) && !defined(PNG_FLOATING_POINT_SUPPORTED) + png_free(png_ptr, info_ptr->scal_s_width); + png_free(png_ptr, info_ptr->scal_s_height); + info_ptr->scal_s_width = NULL; + info_ptr->scal_s_height = NULL; +#endif + info_ptr->valid &= ~PNG_INFO_sCAL; + } +#endif + +#ifdef PNG_pCAL_SUPPORTED + /* Free any pCAL entry */ + if ((mask & PNG_FREE_PCAL) & info_ptr->free_me) + { + png_free(png_ptr, info_ptr->pcal_purpose); + png_free(png_ptr, info_ptr->pcal_units); + info_ptr->pcal_purpose = NULL; + info_ptr->pcal_units = NULL; + if (info_ptr->pcal_params != NULL) + { + int i; + for (i = 0; i < (int)info_ptr->pcal_nparams; i++) + { + png_free(png_ptr, info_ptr->pcal_params[i]); + info_ptr->pcal_params[i] = NULL; + } + png_free(png_ptr, info_ptr->pcal_params); + info_ptr->pcal_params = NULL; + } + info_ptr->valid &= ~PNG_INFO_pCAL; + } +#endif + +#ifdef PNG_iCCP_SUPPORTED + /* Free any iCCP entry */ + if ((mask & PNG_FREE_ICCP) & info_ptr->free_me) + { + png_free(png_ptr, info_ptr->iccp_name); + png_free(png_ptr, info_ptr->iccp_profile); + info_ptr->iccp_name = NULL; + info_ptr->iccp_profile = NULL; + info_ptr->valid &= ~PNG_INFO_iCCP; + } +#endif + +#ifdef PNG_sPLT_SUPPORTED + /* Free a given sPLT entry, or (if num == -1) all sPLT entries */ + if ((mask & PNG_FREE_SPLT) & info_ptr->free_me) + { + if (num != -1) + { + if (info_ptr->splt_palettes) + { + png_free(png_ptr, info_ptr->splt_palettes[num].name); + png_free(png_ptr, info_ptr->splt_palettes[num].entries); + info_ptr->splt_palettes[num].name = NULL; + info_ptr->splt_palettes[num].entries = NULL; + } + } + + else + { + if (info_ptr->splt_palettes_num) + { + int i; + for (i = 0; i < (int)info_ptr->splt_palettes_num; i++) + png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, i); + + png_free(png_ptr, info_ptr->splt_palettes); + info_ptr->splt_palettes = NULL; + info_ptr->splt_palettes_num = 0; + } + info_ptr->valid &= ~PNG_INFO_sPLT; + } + } +#endif + +#ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED + if (png_ptr->unknown_chunk.data) + { + png_free(png_ptr, png_ptr->unknown_chunk.data); + png_ptr->unknown_chunk.data = NULL; + } + + if ((mask & PNG_FREE_UNKN) & info_ptr->free_me) + { + if (num != -1) + { + if (info_ptr->unknown_chunks) + { + png_free(png_ptr, info_ptr->unknown_chunks[num].data); + info_ptr->unknown_chunks[num].data = NULL; + } + } + + else + { + int i; + + if (info_ptr->unknown_chunks_num) + { + for (i = 0; i < info_ptr->unknown_chunks_num; i++) + png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, i); + + png_free(png_ptr, info_ptr->unknown_chunks); + info_ptr->unknown_chunks = NULL; + info_ptr->unknown_chunks_num = 0; + } + } + } +#endif + +#ifdef PNG_hIST_SUPPORTED + /* Free any hIST entry */ + if ((mask & PNG_FREE_HIST) & info_ptr->free_me) + { + png_free(png_ptr, info_ptr->hist); + info_ptr->hist = NULL; + info_ptr->valid &= ~PNG_INFO_hIST; + } +#endif + + /* Free any PLTE entry that was internally allocated */ + if ((mask & PNG_FREE_PLTE) & info_ptr->free_me) + { + png_zfree(png_ptr, info_ptr->palette); + info_ptr->palette = NULL; + info_ptr->valid &= ~PNG_INFO_PLTE; + info_ptr->num_palette = 0; + } + +#ifdef PNG_INFO_IMAGE_SUPPORTED + /* Free any image bits attached to the info structure */ + if ((mask & PNG_FREE_ROWS) & info_ptr->free_me) + { + if (info_ptr->row_pointers) + { + int row; + for (row = 0; row < (int)info_ptr->height; row++) + { + png_free(png_ptr, info_ptr->row_pointers[row]); + info_ptr->row_pointers[row] = NULL; + } + png_free(png_ptr, info_ptr->row_pointers); + info_ptr->row_pointers = NULL; + } + info_ptr->valid &= ~PNG_INFO_IDAT; + } +#endif + + if (num != -1) + mask &= ~PNG_FREE_MUL; + + info_ptr->free_me &= ~mask; +} + +/* This is an internal routine to free any memory that the info struct is + * pointing to before re-using it or freeing the struct itself. Recall + * that png_free() checks for NULL pointers for us. + */ +void /* PRIVATE */ +png_info_destroy(png_structp png_ptr, png_infop info_ptr) +{ + png_debug(1, "in png_info_destroy"); + + png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1); + +#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED + if (png_ptr->num_chunk_list) + { + png_free(png_ptr, png_ptr->chunk_list); + png_ptr->chunk_list = NULL; + png_ptr->num_chunk_list = 0; + } +#endif + + png_info_init_3(&info_ptr, png_sizeof(png_info)); +} +#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */ + +/* This function returns a pointer to the io_ptr associated with the user + * functions. The application should free any memory associated with this + * pointer before png_write_destroy() or png_read_destroy() are called. + */ +png_voidp PNGAPI +png_get_io_ptr(png_structp png_ptr) +{ + if (png_ptr == NULL) + return (NULL); + + return (png_ptr->io_ptr); +} + +#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) +# ifdef PNG_STDIO_SUPPORTED +/* Initialize the default input/output functions for the PNG file. If you + * use your own read or write routines, you can call either png_set_read_fn() + * or png_set_write_fn() instead of png_init_io(). If you have defined + * PNG_NO_STDIO, you must use a function of your own because "FILE *" isn't + * necessarily available. + */ +void PNGAPI +png_init_io(png_structp png_ptr, png_FILE_p fp) +{ + png_debug(1, "in png_init_io"); + + if (png_ptr == NULL) + return; + + png_ptr->io_ptr = (png_voidp)fp; +} +# endif + +# ifdef PNG_TIME_RFC1123_SUPPORTED +/* Convert the supplied time into an RFC 1123 string suitable for use in + * a "Creation Time" or other text-based time string. + */ +png_const_charp PNGAPI +png_convert_to_rfc1123(png_structp png_ptr, png_const_timep ptime) +{ + static PNG_CONST char short_months[12][4] = + {"Jan", "Feb", "Mar", "Apr", "May", "Jun", + "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}; + + if (png_ptr == NULL) + return (NULL); + + if (png_ptr->time_buffer == NULL) + { + png_ptr->time_buffer = (png_charp)png_malloc(png_ptr, (png_uint_32)(29* + png_sizeof(char))); + } + +# ifdef USE_FAR_KEYWORD + { + char near_time_buf[29]; + png_snprintf6(near_time_buf, 29, "%d %s %d %02d:%02d:%02d +0000", + ptime->day % 32, short_months[(ptime->month - 1) % 12], + ptime->year, ptime->hour % 24, ptime->minute % 60, + ptime->second % 61); + png_memcpy(png_ptr->time_buffer, near_time_buf, + 29*png_sizeof(char)); + } +# else + png_snprintf6(png_ptr->time_buffer, 29, "%d %s %d %02d:%02d:%02d +0000", + ptime->day % 32, short_months[(ptime->month - 1) % 12], + ptime->year, ptime->hour % 24, ptime->minute % 60, + ptime->second % 61); +# endif + return png_ptr->time_buffer; +} +# endif /* PNG_TIME_RFC1123_SUPPORTED */ + +#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */ + +png_const_charp PNGAPI +png_get_copyright(png_const_structp png_ptr) +{ + PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ +#ifdef PNG_STRING_COPYRIGHT + return PNG_STRING_COPYRIGHT +#else +# ifdef __STDC__ + return PNG_STRING_NEWLINE \ + "libpng version 1.5.1 - February 3, 2011" PNG_STRING_NEWLINE \ + "Copyright (c) 1998-2011 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \ + "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \ + "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \ + PNG_STRING_NEWLINE; +# else + return "libpng version 1.5.1 - February 3, 2011\ + Copyright (c) 1998-2011 Glenn Randers-Pehrson\ + Copyright (c) 1996-1997 Andreas Dilger\ + Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc."; +# endif +#endif +} + +/* The following return the library version as a short string in the + * format 1.0.0 through 99.99.99zz. To get the version of *.h files + * used with your application, print out PNG_LIBPNG_VER_STRING, which + * is defined in png.h. + * Note: now there is no difference between png_get_libpng_ver() and + * png_get_header_ver(). Due to the version_nn_nn_nn typedef guard, + * it is guaranteed that png.c uses the correct version of png.h. + */ +png_const_charp PNGAPI +png_get_libpng_ver(png_const_structp png_ptr) +{ + /* Version of *.c files used when building libpng */ + return png_get_header_ver(png_ptr); +} + +png_const_charp PNGAPI +png_get_header_ver(png_const_structp png_ptr) +{ + /* Version of *.h files used when building libpng */ + PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ + return PNG_LIBPNG_VER_STRING; +} + +png_const_charp PNGAPI +png_get_header_version(png_const_structp png_ptr) +{ + /* Returns longer string containing both version and date */ + PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ +#ifdef __STDC__ + return PNG_HEADER_VERSION_STRING +# ifndef PNG_READ_SUPPORTED + " (NO READ SUPPORT)" +# endif + PNG_STRING_NEWLINE; +#else + return PNG_HEADER_VERSION_STRING; +#endif +} + +#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) +# ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED +int PNGAPI +png_handle_as_unknown(png_structp png_ptr, png_const_bytep chunk_name) +{ + /* Check chunk_name and return "keep" value if it's on the list, else 0 */ + int i; + png_bytep p; + if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list<=0) + return 0; + + p = png_ptr->chunk_list + png_ptr->num_chunk_list*5 - 5; + for (i = png_ptr->num_chunk_list; i; i--, p -= 5) + if (!png_memcmp(chunk_name, p, 4)) + return ((int)*(p + 4)); + return 0; +} +# endif +#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */ + +#ifdef PNG_READ_SUPPORTED +/* This function, added to libpng-1.0.6g, is untested. */ +int PNGAPI +png_reset_zstream(png_structp png_ptr) +{ + if (png_ptr == NULL) + return Z_STREAM_ERROR; + + return (inflateReset(&png_ptr->zstream)); +} +#endif /* PNG_READ_SUPPORTED */ + +/* This function was added to libpng-1.0.7 */ +png_uint_32 PNGAPI +png_access_version_number(void) +{ + /* Version of *.c files used when building libpng */ + return((png_uint_32)PNG_LIBPNG_VER); +} + + + +#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) +# ifdef PNG_SIZE_T +/* Added at libpng version 1.2.6 */ + PNG_EXTERN png_size_t PNGAPI png_convert_size PNGARG((size_t size)); +png_size_t PNGAPI +png_convert_size(size_t size) +{ + if (size > (png_size_t)-1) + PNG_ABORT(); /* We haven't got access to png_ptr, so no png_error() */ + + return ((png_size_t)size); +} +# endif /* PNG_SIZE_T */ + +/* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */ +# ifdef PNG_CHECK_cHRM_SUPPORTED + +int /* PRIVATE */ +png_check_cHRM_fixed(png_structp png_ptr, + png_fixed_point white_x, png_fixed_point white_y, png_fixed_point red_x, + png_fixed_point red_y, png_fixed_point green_x, png_fixed_point green_y, + png_fixed_point blue_x, png_fixed_point blue_y) +{ + int ret = 1; + unsigned long xy_hi,xy_lo,yx_hi,yx_lo; + + png_debug(1, "in function png_check_cHRM_fixed"); + + if (png_ptr == NULL) + return 0; + + if (white_x < 0 || white_y <= 0 || + red_x < 0 || red_y < 0 || + green_x < 0 || green_y < 0 || + blue_x < 0 || blue_y < 0) + { + png_warning(png_ptr, + "Ignoring attempt to set negative chromaticity value"); + ret = 0; + } + if (white_x > (png_fixed_point)PNG_UINT_31_MAX || + white_y > (png_fixed_point)PNG_UINT_31_MAX || + red_x > (png_fixed_point)PNG_UINT_31_MAX || + red_y > (png_fixed_point)PNG_UINT_31_MAX || + green_x > (png_fixed_point)PNG_UINT_31_MAX || + green_y > (png_fixed_point)PNG_UINT_31_MAX || + blue_x > (png_fixed_point)PNG_UINT_31_MAX || + blue_y > (png_fixed_point)PNG_UINT_31_MAX ) + { + png_warning(png_ptr, + "Ignoring attempt to set chromaticity value exceeding 21474.83"); + ret = 0; + } + if (white_x > 100000L - white_y) + { + png_warning(png_ptr, "Invalid cHRM white point"); + ret = 0; + } + + if (red_x > 100000L - red_y) + { + png_warning(png_ptr, "Invalid cHRM red point"); + ret = 0; + } + + if (green_x > 100000L - green_y) + { + png_warning(png_ptr, "Invalid cHRM green point"); + ret = 0; + } + + if (blue_x > 100000L - blue_y) + { + png_warning(png_ptr, "Invalid cHRM blue point"); + ret = 0; + } + + png_64bit_product(green_x - red_x, blue_y - red_y, &xy_hi, &xy_lo); + png_64bit_product(green_y - red_y, blue_x - red_x, &yx_hi, &yx_lo); + + if (xy_hi == yx_hi && xy_lo == yx_lo) + { + png_warning(png_ptr, + "Ignoring attempt to set cHRM RGB triangle with zero area"); + ret = 0; + } + + return ret; +} +# endif /* PNG_CHECK_cHRM_SUPPORTED */ + +void /* PRIVATE */ +png_check_IHDR(png_structp png_ptr, + png_uint_32 width, png_uint_32 height, int bit_depth, + int color_type, int interlace_type, int compression_type, + int filter_type) +{ + int error = 0; + + /* Check for width and height valid values */ + if (width == 0) + { + png_warning(png_ptr, "Image width is zero in IHDR"); + error = 1; + } + + if (height == 0) + { + png_warning(png_ptr, "Image height is zero in IHDR"); + error = 1; + } + +# ifdef PNG_SET_USER_LIMITS_SUPPORTED + if (width > png_ptr->user_width_max || width > PNG_USER_WIDTH_MAX) + +# else + if (width > PNG_USER_WIDTH_MAX) +# endif + { + png_warning(png_ptr, "Image width exceeds user limit in IHDR"); + error = 1; + } + +# ifdef PNG_SET_USER_LIMITS_SUPPORTED + if (height > png_ptr->user_height_max || height > PNG_USER_HEIGHT_MAX) +# else + if (height > PNG_USER_HEIGHT_MAX) +# endif + { + png_warning(png_ptr, "Image height exceeds user limit in IHDR"); + error = 1; + } + + if (width > PNG_UINT_31_MAX) + { + png_warning(png_ptr, "Invalid image width in IHDR"); + error = 1; + } + + if (height > PNG_UINT_31_MAX) + { + png_warning(png_ptr, "Invalid image height in IHDR"); + error = 1; + } + + if (width > (PNG_UINT_32_MAX + >> 3) /* 8-byte RGBA pixels */ + - 48 /* bigrowbuf hack */ + - 1 /* filter byte */ + - 7*8 /* rounding of width to multiple of 8 pixels */ + - 8) /* extra max_pixel_depth pad */ + png_warning(png_ptr, "Width is too large for libpng to process pixels"); + + /* Check other values */ + if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 && + bit_depth != 8 && bit_depth != 16) + { + png_warning(png_ptr, "Invalid bit depth in IHDR"); + error = 1; + } + + if (color_type < 0 || color_type == 1 || + color_type == 5 || color_type > 6) + { + png_warning(png_ptr, "Invalid color type in IHDR"); + error = 1; + } + + if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) || + ((color_type == PNG_COLOR_TYPE_RGB || + color_type == PNG_COLOR_TYPE_GRAY_ALPHA || + color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8)) + { + png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR"); + error = 1; + } + + if (interlace_type >= PNG_INTERLACE_LAST) + { + png_warning(png_ptr, "Unknown interlace method in IHDR"); + error = 1; + } + + if (compression_type != PNG_COMPRESSION_TYPE_BASE) + { + png_warning(png_ptr, "Unknown compression method in IHDR"); + error = 1; + } + +# ifdef PNG_MNG_FEATURES_SUPPORTED + /* Accept filter_method 64 (intrapixel differencing) only if + * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and + * 2. Libpng did not read a PNG signature (this filter_method is only + * used in PNG datastreams that are embedded in MNG datastreams) and + * 3. The application called png_permit_mng_features with a mask that + * included PNG_FLAG_MNG_FILTER_64 and + * 4. The filter_method is 64 and + * 5. The color_type is RGB or RGBA + */ + if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) && + png_ptr->mng_features_permitted) + png_warning(png_ptr, "MNG features are not allowed in a PNG datastream"); + + if (filter_type != PNG_FILTER_TYPE_BASE) + { + if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) && + (filter_type == PNG_INTRAPIXEL_DIFFERENCING) && + ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) && + (color_type == PNG_COLOR_TYPE_RGB || + color_type == PNG_COLOR_TYPE_RGB_ALPHA))) + { + png_warning(png_ptr, "Unknown filter method in IHDR"); + error = 1; + } + + if (png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) + { + png_warning(png_ptr, "Invalid filter method in IHDR"); + error = 1; + } + } + +# else + if (filter_type != PNG_FILTER_TYPE_BASE) + { + png_warning(png_ptr, "Unknown filter method in IHDR"); + error = 1; + } +# endif + + if (error == 1) + png_error(png_ptr, "Invalid IHDR data"); +} + +#if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED) +/* ASCII to fp functions */ +/* Check an ASCII formated floating point value, see the more detailed + * comments in pngpriv.h + */ +/* The following is used internally to preserve the 'valid' flag */ +#define png_fp_add(state, flags) ((state) |= (flags)) +#define png_fp_set(state, value)\ + ((state) = (value) | ((state) & PNG_FP_WAS_VALID)) + +/* Internal type codes: bits above the base state! */ +#define PNG_FP_SIGN 0 /* [+-] */ +#define PNG_FP_DOT 4 /* . */ +#define PNG_FP_DIGIT 8 /* [0123456789] */ +#define PNG_FP_E 12 /* [Ee] */ + +int /* PRIVATE */ +png_check_fp_number(png_const_charp string, png_size_t size, int *statep, + png_size_tp whereami) +{ + int state = *statep; + png_size_t i = *whereami; + + while (i < size) + { + int type; + /* First find the type of the next character */ + { + char ch = string[i]; + + if (ch >= 48 && ch <= 57) + type = PNG_FP_DIGIT; + + else switch (ch) + { + case 43: case 45: type = PNG_FP_SIGN; break; + case 46: type = PNG_FP_DOT; break; + case 69: case 101: type = PNG_FP_E; break; + default: goto PNG_FP_End; + } + } + + /* Now deal with this type according to the current + * state, the type is arranged to not overlap the + * bits of the PNG_FP_STATE. + */ + switch ((state & PNG_FP_STATE) + type) + { + case PNG_FP_INTEGER + PNG_FP_SIGN: + if (state & PNG_FP_SAW_ANY) + goto PNG_FP_End; /* not a part of the number */ + + png_fp_add(state, PNG_FP_SAW_SIGN); + break; + + case PNG_FP_INTEGER + PNG_FP_DOT: + /* Ok as trailer, ok as lead of fraction. */ + if (state & PNG_FP_SAW_DOT) /* two dots */ + goto PNG_FP_End; + + else if (state & PNG_FP_SAW_DIGIT) /* trailing dot? */ + png_fp_add(state, PNG_FP_SAW_DOT); + + else + png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT); + + break; + + case PNG_FP_INTEGER + PNG_FP_DIGIT: + if (state & PNG_FP_SAW_DOT) /* delayed fraction */ + png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT); + + png_fp_add(state, PNG_FP_SAW_DIGIT + PNG_FP_WAS_VALID); + + break; + case PNG_FP_INTEGER + PNG_FP_E: + if ((state & PNG_FP_SAW_DIGIT) == 0) + goto PNG_FP_End; + + png_fp_set(state, PNG_FP_EXPONENT); + + break; + + /* case PNG_FP_FRACTION + PNG_FP_SIGN: + goto PNG_FP_End; ** no sign in exponent */ + + /* case PNG_FP_FRACTION + PNG_FP_DOT: + goto PNG_FP_End; ** Because SAW_DOT is always set */ + + case PNG_FP_FRACTION + PNG_FP_DIGIT: + png_fp_add(state, PNG_FP_SAW_DIGIT + PNG_FP_WAS_VALID); + break; + + case PNG_FP_FRACTION + PNG_FP_E: + /* This is correct because the trailing '.' on an + * integer is handled above - so we can only get here + * with the sequence ".E" (with no preceding digits). + */ + if ((state & PNG_FP_SAW_DIGIT) == 0) + goto PNG_FP_End; + + png_fp_set(state, PNG_FP_EXPONENT); + + break; + + case PNG_FP_EXPONENT + PNG_FP_SIGN: + if (state & PNG_FP_SAW_ANY) + goto PNG_FP_End; /* not a part of the number */ + + png_fp_add(state, PNG_FP_SAW_SIGN); + + break; + + /* case PNG_FP_EXPONENT + PNG_FP_DOT: + goto PNG_FP_End; */ + + case PNG_FP_EXPONENT + PNG_FP_DIGIT: + png_fp_add(state, PNG_FP_SAW_DIGIT + PNG_FP_WAS_VALID); + + break; + + /* case PNG_FP_EXPONEXT + PNG_FP_E: + goto PNG_FP_End; */ + + default: goto PNG_FP_End; /* I.e. break 2 */ + } + + /* The character seems ok, continue. */ + ++i; + } + +PNG_FP_End: + /* Here at the end, update the state and return the correct + * return code. + */ + *statep = state; + *whereami = i; + + return (state & PNG_FP_SAW_DIGIT) != 0; +} + + +/* The same but for a complete string. */ +int +png_check_fp_string(png_const_charp string, png_size_t size) +{ + int state=0; + png_size_t char_index=0; + + return png_check_fp_number(string, size, &state, &char_index) && + (char_index == size || string[char_index] == 0); +} +#endif /* pCAL or sCAL */ + +#ifdef PNG_READ_sCAL_SUPPORTED +# ifdef PNG_FLOATING_POINT_SUPPORTED +/* Utility used below - a simple accurate power of ten from an integral + * exponent. + */ +static double +png_pow10(int power) +{ + int recip = 0; + double d = 1; + + /* Handle negative exponent with a reciprocal at the end because + * 10 is exact whereas .1 is inexact in base 2 + */ + if (power < 0) + { + if (power < DBL_MIN_10_EXP) return 0; + recip = 1, power = -power; + } + + if (power > 0) + { + /* Decompose power bitwise. */ + double mult = 10; + do + { + if (power & 1) d *= mult; + mult *= mult; + power >>= 1; + } + while (power > 0); + + if (recip) d = 1/d; + } + /* else power is 0 and d is 1 */ + + return d; +} + +/* Function to format a floating point value in ASCII with a given + * precision. + */ +void /* PRIVATE */ +png_ascii_from_fp(png_structp png_ptr, png_charp ascii, png_size_t size, + double fp, unsigned int precision) +{ + /* We use standard functions from math.h, but not printf because + * that would require stdio. The caller must supply a buffer of + * sufficient size or we will png_error. The tests on size and + * the space in ascii[] consumed are indicated below. + */ + if (precision < 1) + precision = DBL_DIG; + + /* Enforce the limit of the implementation precision too. */ + if (precision > DBL_DIG+1) + precision = DBL_DIG+1; + + /* Basic sanity checks */ + if (size >= precision+5) /* See the requirements below. */ + { + if (fp < 0) + { + fp = -fp; + *ascii++ = 45; /* '-' PLUS 1 TOTAL 1*/ + --size; + } + + if (fp >= DBL_MIN && fp <= DBL_MAX) + { + int exp_b10; /* A base 10 exponent */ + double base; /* 10^exp_b10 */ + + /* First extract a base 10 exponent of the number, + * the calculation below rounds down when converting + * from base 2 to base 10 (multiply by log10(2) - + * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to + * be increased. Note that the arithmetic shift + * performs a floor() unlike C arithmetic - using a + * C multiply would break the following for negative + * exponents. + */ + (void)frexp(fp, &exp_b10); /* exponent to base 2 */ + + exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */ + + /* Avoid underflow here. */ + base = png_pow10(exp_b10); /* May underflow */ + + while (base < DBL_MIN || base < fp) + { + /* And this may overflow. */ + double test = png_pow10(exp_b10+1); + + if (test <= DBL_MAX) + ++exp_b10, base = test; + + else + break; + } + + /* Normalize fp and correct exp_b10, after this fp is in the + * range [.1,1) and exp_b10 is both the exponent and the digit + * *before* which the decimal point should be inserted + * (starting with 0 for the first digit). Note that this + * works even if 10^exp_b10 is out of range because of the + * test on DBL_MAX above. + */ + fp /= base; + while (fp >= 1) fp /= 10, ++exp_b10; + + /* Because of the code above fp may, at this point, be + * less than .1, this is ok because the code below can + * handle the leading zeros this generates, so no attempt + * is made to correct that here. + */ + + { + int czero, clead, cdigits; + char exponent[10]; + + /* Allow up to two leading zeros - this will not lengthen + * the number compared to using E-n. + */ + if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */ + { + czero = -exp_b10; /* PLUS 2 digits: TOTAL 3 */ + exp_b10 = 0; /* Dot added below before first output. */ + } + else + czero = 0; /* No zeros to add */ + + /* Generate the digit list, stripping trailing zeros and + * inserting a '.' before a digit if the exponent is 0. + */ + clead = czero; /* Count of leading zeros */ + cdigits = 0; /* Count of digits in list. */ + + do + { + double d; + + fp *= 10; + /* Use modf here, not floor and subtract, so that + * the separation is done in one step. At the end + * of the loop don't break the number into parts so + * that the final digit is rounded. + */ + if (cdigits+czero-clead+1 < (int)precision) + fp = modf(fp, &d); + + else + { + d = floor(fp + .5); + + if (d > 9) + { + /* Rounding up to 10, handle that here. */ + if (czero > 0) + { + --czero, d = 1; + if (cdigits == 0) --clead; + } + else + { + while (cdigits > 0 && d > 9) + { + int ch = *--ascii; + + if (exp_b10 != (-1)) + ++exp_b10; + + else if (ch == 46) + { + ch = *--ascii, ++size; + /* Advance exp_b10 to '1', so that the + * decimal point happens after the + * previous digit. + */ + exp_b10 = 1; + } + + --cdigits; + d = ch - 47; /* I.e. 1+(ch-48) */ + } + + /* Did we reach the beginning? If so adjust the + * exponent but take into account the leading + * decimal point. + */ + if (d > 9) /* cdigits == 0 */ + { + if (exp_b10 == (-1)) + { + /* Leading decimal point (plus zeros?), if + * we lose the decimal point here it must + * be reentered below. + */ + int ch = *--ascii; + + if (ch == 46) + ++size, exp_b10 = 1; + + /* Else lost a leading zero, so 'exp_b10' is + * still ok at (-1) + */ + } + else + ++exp_b10; + + /* In all cases we output a '1' */ + d = 1; + } + } + } + fp = 0; /* Guarantees termination below. */ + } + + if (d == 0) + { + ++czero; + if (cdigits == 0) ++clead; + } + else + { + /* Included embedded zeros in the digit count. */ + cdigits += czero - clead; + clead = 0; + + while (czero > 0) + { + /* exp_b10 == (-1) means we just output the decimal + * place - after the DP don't adjust 'exp_b10' any + * more! + */ + if (exp_b10 != (-1)) + { + if (exp_b10 == 0) *ascii++ = 46, --size; + /* PLUS 1: TOTAL 4 */ + --exp_b10; + } + *ascii++ = 48, --czero; + } + + if (exp_b10 != (-1)) + { + if (exp_b10 == 0) *ascii++ = 46, --size; /* counted + above */ + --exp_b10; + } + *ascii++ = (char)(48 + (int)d), ++cdigits; + } + } + while (cdigits+czero-clead < (int)precision && fp > DBL_MIN); + + /* The total output count (max) is now 4+precision */ + + /* Check for an exponent, if we don't need one we are + * done and just need to terminate the string. At + * this point exp_b10==(-1) is effectively if flag - it got + * to '-1' because of the decrement after outputing + * the decimal point above (the exponent required is + * *not* -1!) + */ + if (exp_b10 >= (-1) && exp_b10 <= 2) + { + /* The following only happens if we didn't output the + * leading zeros above for negative exponent, so this + * doest add to the digit requirement. Note that the + * two zeros here can only be output if the two leading + * zeros were *not* output, so this doesn't increase + * the output count. + */ + while (--exp_b10 >= 0) *ascii++ = 48; + + *ascii = 0; + + /* Total buffer requirement (including the '\0') is + * 5+precision - see check at the start. + */ + return; + } + + /* Here if an exponent is required, adjust size for + * the digits we output but did not count. The total + * digit output here so far is at most 1+precision - no + * decimal point and no leading or trailing zeros have + * been output. + */ + size -= cdigits; + + *ascii++ = 69, --size; /* 'E': PLUS 1 TOTAL 2+precision*/ + if (exp_b10 < 0) + { + *ascii++ = 45, --size; /* '-': PLUS 1 TOTAL 3+precision */ + exp_b10 = -exp_b10; + } + + cdigits = 0; + + while (exp_b10 > 0) + { + exponent[cdigits++] = (char)(48 + exp_b10 % 10); + exp_b10 /= 10; + } + + /* Need another size check here for the exponent digits, so + * this need not be considered above. + */ + if ((int)size > cdigits) + { + while (cdigits > 0) *ascii++ = exponent[--cdigits]; + + *ascii = 0; + + return; + } + } + } + else if (!(fp >= DBL_MIN)) + { + *ascii++ = 48; /* '0' */ + *ascii = 0; + return; + } + else + { + *ascii++ = 105; /* 'i' */ + *ascii++ = 110; /* 'n' */ + *ascii++ = 102; /* 'f' */ + *ascii = 0; + return; + } + } + + /* Here on buffer too small. */ + png_error(png_ptr, "ASCII conversion buffer too small"); +} + +# endif /* FLOATING_POINT */ + +# ifdef PNG_FIXED_POINT_SUPPORTED +/* Function to format a fixed point value in ASCII. + */ +void /* PRIVATE */ +png_ascii_from_fixed(png_structp png_ptr, png_charp ascii, png_size_t size, + png_fixed_point fp) +{ + /* Require space for 10 decimal digits, a decimal point, a minus sign and a + * trailing \0, 13 characters: + */ + if (size > 12) + { + png_uint_32 num; + + /* Avoid overflow here on the minimum integer. */ + if (fp < 0) + *ascii++ = 45, --size, num = -fp; + else + num = fp; + + if (num <= 0x80000000U) /* else overflowed */ + { + unsigned int ndigits = 0, first = 16/*flag value*/; + char digits[10]; + + while (num) + { + /* Split the low digit off num: */ + unsigned int tmp = num/10; + num -= tmp*10; + digits[ndigits++] = (char)(48 + num); + /* Record the first non-zero digit, note that this is a number + * starting at 1, it's not actually the array index. + */ + if (first == 16 && num > 0) + first = ndigits; + num = tmp; + } + + if (ndigits > 0) + { + while (ndigits > 5) *ascii++ = digits[--ndigits]; + /* The remaining digits are fractional digits, ndigits is '5' or + * smaller at this point. It is certainly not zero. Check for a + * non-zero fractional digit: + */ + if (first <= 5) + { + unsigned int i; + *ascii++ = 46; /* decimal point */ + /* ndigits may be <5 for small numbers, output leading zeros + * then ndigits digits to first: + */ + i = 5; + while (ndigits < i) *ascii++ = 48, --i; + while (ndigits >= first) *ascii++ = digits[--ndigits]; + /* Don't output the trailing zeros! */ + } + } + else + *ascii++ = 48; + + /* And null terminate the string: */ + *ascii = 0; + return; + } + } + + /* Here on buffer too small. */ + png_error(png_ptr, "ASCII conversion buffer too small"); +} +# endif /* FIXED_POINT */ +#endif /* READ_SCAL */ + +#if defined(PNG_FLOATING_POINT_SUPPORTED) && \ + !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) +png_fixed_point +png_fixed(png_structp png_ptr, double fp, png_const_charp text) +{ + double r = floor(100000 * fp + .5); + + if (r > 2147483647. || r < -2147483648.) + png_fixed_error(png_ptr, text); + + return (png_fixed_point)r; +} +#endif + +#if defined(PNG_READ_GAMMA_SUPPORTED) || \ + defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG__READ_pHYs_SUPPORTED) +/* muldiv functions */ +/* This API takes signed arguments and rounds the result to the nearest + * integer (or, for a fixed point number - the standard argument - to + * the nearest .00001). Overflow and divide by zero are signalled in + * the result, a boolean - true on success, false on overflow. + */ +int +png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times, + png_int_32 divisor) +{ + /* Return a * times / divisor, rounded. */ + if (divisor != 0) + { + if (a == 0 || times == 0) + { + *res = 0; + return 1; + } + else + { +#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED + double r = a; + r *= times; + r /= divisor; + r = floor(r+.5); + + /* A png_fixed_point is a 32 bit integer. */ + if (r <= 2147483647. && r >= -2147483648.) + { + *res = (png_fixed_point)r; + return 1; + } +#else + int negative = 0; + png_uint_32 A, T, D; + png_uint_32 s16, s32, s00; + + if (a < 0) + negative = 1, A = -a; + else + A = a; + + if (times < 0) + negative = !negative, T = -times; + else + T = times; + + if (divisor < 0) + negative = !negative, D = -divisor; + else + D = divisor; + + /* Following can't overflow because the arguments only + * have 31 bits each, however the result may be 32 bits. + */ + s16 = (A >> 16) * (T & 0xffff) + + (A & 0xffff) * (T >> 16); + /* Can't overflow because the a*times bit is only 30 + * bits at most. + */ + s32 = (A >> 16) * (T >> 16) + (s16 >> 16); + s00 = (A & 0xffff) * (T & 0xffff); + + s16 = (s16 & 0xffff) << 16; + s00 += s16; + + if (s00 < s16) + ++s32; /* carry */ + + if (s32 < D) /* else overflow */ + { + /* s32.s00 is now the 64 bit product, do a standard + * division, we know that s32 < D, so the maximum + * required shift is 31. + */ + int bitshift = 32; + png_fixed_point result = 0; /* NOTE: signed */ + + while (--bitshift >= 0) + { + png_uint_32 d32, d00; + + if (bitshift > 0) + d32 = D >> (32-bitshift), d00 = D << bitshift; + + else + d32 = 0, d00 = D; + + if (s32 > d32) + { + if (s00 < d00) --s32; /* carry */ + s32 -= d32, s00 -= d00, result += 1<<bitshift; + } + + else + if (s32 == d32 && s00 >= d00) + s32 = 0, s00 -= d00, result += 1<<bitshift; + } + + /* Handle the rounding. */ + if (s00 >= (D >> 1)) + ++result; + + if (negative) + result = -result; + + /* Check for overflow. */ + if ((negative && result <= 0) || (!negative && result >= 0)) + { + *res = result; + return 1; + } + } +#endif + } + } + + return 0; +} +#endif /* READ_GAMMA || INCH_CONVERSIONS */ + +#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED) +/* The following is for when the caller doesn't much care about the + * result. + */ +png_fixed_point +png_muldiv_warn(png_structp png_ptr, png_fixed_point a, png_int_32 times, + png_int_32 divisor) +{ + png_fixed_point result; + + if (png_muldiv(&result, a, times, divisor)) + return result; + + png_warning(png_ptr, "fixed point overflow ignored"); + return 0; +} +#endif + +#ifdef PNG_READ_GAMMA_SUPPORTED /* more fixed point functions for gammma */ +/* Calculate a reciprocal, return 0 on div-by-zero or overflow. */ +png_fixed_point +png_reciprocal(png_fixed_point a) +{ +#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED + double r = floor(1E10/a+.5); + + if (r <= 2147483647. && r >= -2147483648.) + return (png_fixed_point)r; +#else + png_fixed_point res; + + if (png_muldiv(&res, 100000, 100000, a)) + return res; +#endif + + return 0; /* error/overflow */ +} + +/* A local convenience routine. */ +static png_fixed_point +png_product2(png_fixed_point a, png_fixed_point b) +{ + /* The required result is 1/a * 1/b; the following preserves accuracy. */ +#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED + double r = a * 1E-5; + r *= b; + r = floor(r+.5); + + if (r <= 2147483647. && r >= -2147483648.) + return (png_fixed_point)r; +#else + png_fixed_point res; + + if (png_muldiv(&res, a, b, 100000)) + return res; +#endif + + return 0; /* overflow */ +} + +/* The inverse of the above. */ +png_fixed_point +png_reciprocal2(png_fixed_point a, png_fixed_point b) +{ + /* The required result is 1/a * 1/b; the following preserves accuracy. */ +#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED + double r = 1E15/a; + r /= b; + r = floor(r+.5); + + if (r <= 2147483647. && r >= -2147483648.) + return (png_fixed_point)r; +#else + /* This may overflow because the range of png_fixed_point isn't symmetric, + * but this API is only used for the product of file and screen gamma so it + * doesn't matter that the smallest number it can produce is 1/21474, not + * 1/100000 + */ + png_fixed_point res = png_product2(a, b); + + if (res != 0) + return png_reciprocal(res); +#endif + + return 0; /* overflow */ +} +#endif /* READ_GAMMA */ + +#ifdef PNG_CHECK_cHRM_SUPPORTED +/* Added at libpng version 1.2.34 (Dec 8, 2008) and 1.4.0 (Jan 2, + * 2010: moved from pngset.c) */ +/* + * Multiply two 32-bit numbers, V1 and V2, using 32-bit + * arithmetic, to produce a 64 bit result in the HI/LO words. + * + * A B + * x C D + * ------ + * AD || BD + * AC || CB || 0 + * + * where A and B are the high and low 16-bit words of V1, + * C and D are the 16-bit words of V2, AD is the product of + * A and D, and X || Y is (X << 16) + Y. +*/ + +void /* PRIVATE */ +png_64bit_product (long v1, long v2, unsigned long *hi_product, + unsigned long *lo_product) +{ + int a, b, c, d; + long lo, hi, x, y; + + a = (v1 >> 16) & 0xffff; + b = v1 & 0xffff; + c = (v2 >> 16) & 0xffff; + d = v2 & 0xffff; + + lo = b * d; /* BD */ + x = a * d + c * b; /* AD + CB */ + y = ((lo >> 16) & 0xffff) + x; + + lo = (lo & 0xffff) | ((y & 0xffff) << 16); + hi = (y >> 16) & 0xffff; + + hi += a * c; /* AC */ + + *hi_product = (unsigned long)hi; + *lo_product = (unsigned long)lo; +} +#endif /* CHECK_cHRM */ + +#ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */ +#ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED +/* Fixed point gamma. + * + * To calculate gamma this code implements fast log() and exp() calls using only + * fixed point arithmetic. This code has sufficient precision for either 8 or + * 16 bit sample values. + * + * The tables used here were calculated using simple 'bc' programs, but C double + * precision floating point arithmetic would work fine. The programs are given + * at the head of each table. + * + * 8 bit log table + * This is a table of -log(value/255)/log(2) for 'value' in the range 128 to + * 255, so it's the base 2 logarithm of a normalized 8 bit floating point + * mantissa. The numbers are 32 bit fractions. + */ +static png_uint_32 +png_8bit_l2[128] = +{ +# if PNG_DO_BC + for (i=128;i<256;++i) { .5 - l(i/255)/l(2)*65536*65536; } +# endif + 4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U, + 3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U, + 3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U, + 3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U, + 3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U, + 2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U, + 2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U, + 2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U, + 2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U, + 2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U, + 1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U, + 1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U, + 1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U, + 1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U, + 1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U, + 971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U, + 803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U, + 639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U, + 479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U, + 324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U, + 172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U, + 24347096U, 0U +#if 0 + /* The following are the values for 16 bit tables - these work fine for the 8 + * bit conversions but produce very slightly larger errors in the 16 bit log + * (about 1.2 as opposed to 0.7 absolute error in the final value). To use + * these all the shifts below must be adjusted appropriately. + */ + 65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054, + 57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803, + 50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068, + 43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782, + 37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887, + 31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339, + 25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098, + 20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132, + 15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415, + 10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523, + 6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495, + 1119, 744, 372 +#endif +}; + +static png_int_32 +png_log8bit(unsigned int x) +{ + unsigned int lg2 = 0; + /* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log, + * because the log is actually negate that means adding 1. The final + * returned value thus has the range 0 (for 255 input) to 7.994 (for 1 + * input), return 7.99998 for the overflow (log 0) case - so the result is + * always at most 19 bits. + */ + if ((x &= 0xff) == 0) + return 0xffffffff; + + if ((x & 0xf0) == 0) + lg2 = 4, x <<= 4; + + if ((x & 0xc0) == 0) + lg2 += 2, x <<= 2; + + if ((x & 0x80) == 0) + lg2 += 1, x <<= 1; + + /* result is at most 19 bits, so this cast is safe: */ + return (png_int_32)((lg2 << 16) + ((png_8bit_l2[x-128]+32768)>>16)); +} + +/* The above gives exact (to 16 binary places) log2 values for 8 bit images, + * for 16 bit images we use the most significant 8 bits of the 16 bit value to + * get an approximation then multiply the approximation by a correction factor + * determined by the remaining up to 8 bits. This requires an additional step + * in the 16 bit case. + * + * We want log2(value/65535), we have log2(v'/255), where: + * + * value = v' * 256 + v'' + * = v' * f + * + * So f is value/v', which is equal to (256+v''/v') since v' is in the range 128 + * to 255 and v'' is in the range 0 to 255 f will be in the range 256 to less + * than 258. The final factor also needs to correct for the fact that our 8 bit + * value is scaled by 255, whereas the 16 bit values must be scaled by 65535. + * + * This gives a final formula using a calculated value 'x' which is value/v' and + * scaling by 65536 to match the above table: + * + * log2(x/257) * 65536 + * + * Since these numbers are so close to '1' we can use simple linear + * interpolation between the two end values 256/257 (result -368.61) and 258/257 + * (result 367.179). The values used below are scaled by a further 64 to give + * 16 bit precision in the interpolation: + * + * Start (256): -23591 + * Zero (257): 0 + * End (258): 23499 + */ +static png_int_32 +png_log16bit(png_uint_32 x) +{ + unsigned int lg2 = 0; + + /* As above, but now the input has 16 bits. */ + if ((x &= 0xffff) == 0) + return 0xffffffff; + + if ((x & 0xff00) == 0) + lg2 = 8, x <<= 8; + + if ((x & 0xf000) == 0) + lg2 += 4, x <<= 4; + + if ((x & 0xc000) == 0) + lg2 += 2, x <<= 2; + + if ((x & 0x8000) == 0) + lg2 += 1, x <<= 1; + + /* Calculate the base logarithm from the top 8 bits as a 28 bit fractional + * value. + */ + lg2 <<= 28; + lg2 += (png_8bit_l2[(x>>8)-128]+8) >> 4; + + /* Now we need to interpolate the factor, this requires a division by the top + * 8 bits. Do this with maximum precision. + */ + x = ((x << 16) + (x >> 9)) / (x >> 8); + + /* Since we divided by the top 8 bits of 'x' there will be a '1' at 1<<24, + * the value at 1<<16 (ignoring this) will be 0 or 1; this gives us exactly + * 16 bits to interpolate to get the low bits of the result. Round the + * answer. Note that the end point values are scaled by 64 to retain overall + * precision and that 'lg2' is current scaled by an extra 12 bits, so adjust + * the overall scaling by 6-12. Round at every step. + */ + x -= 1U << 24; + + if (x <= 65536U) /* <= '257' */ + lg2 += ((23591U * (65536U-x)) + (1U << (16+6-12-1))) >> (16+6-12); + + else + lg2 -= ((23499U * (x-65536U)) + (1U << (16+6-12-1))) >> (16+6-12); + + /* Safe, because the result can't have more than 20 bits: */ + return (png_int_32)((lg2 + 2048) >> 12); +} + +/* The 'exp()' case must invert the above, taking a 20 bit fixed point + * logarithmic value and returning a 16 or 8 bit number as appropriate. In + * each case only the low 16 bits are relevant - the fraction - since the + * integer bits (the top 4) simply determine a shift. + * + * The worst case is the 16 bit distinction between 65535 and 65534, this + * requires perhaps spurious accuracty in the decoding of the logarithm to + * distinguish log2(65535/65534.5) - 10^-5 or 17 bits. There is little chance + * of getting this accuracy in practice. + * + * To deal with this the following exp() function works out the exponent of the + * frational part of the logarithm by using an accurate 32 bit value from the + * top four fractional bits then multiplying in the remaining bits. + */ +static png_uint_32 +png_32bit_exp[16] = +{ +# if PNG_DO_BC + for (i=0;i<16;++i) { .5 + e(-i/16*l(2))*2^32; } +# endif + /* NOTE: the first entry is deliberately set to the maximum 32 bit value. */ + 4294967295U, 4112874773U, 3938502376U, 3771522796U, 3611622603U, 3458501653U, + 3311872529U, 3171459999U, 3037000500U, 2908241642U, 2784941738U, 2666869345U, + 2553802834U, 2445529972U, 2341847524U, 2242560872U +}; + +/* Adjustment table; provided to explain the numbers in the code below. */ +#if PNG_DO_BC +for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"} + 11 44937.64284865548751208448 + 10 45180.98734845585101160448 + 9 45303.31936980687359311872 + 8 45364.65110595323018870784 + 7 45395.35850361789624614912 + 6 45410.72259715102037508096 + 5 45418.40724413220722311168 + 4 45422.25021786898173001728 + 3 45424.17186732298419044352 + 2 45425.13273269940811464704 + 1 45425.61317555035558641664 + 0 45425.85339951654943850496 +#endif + +static png_uint_32 +png_exp(png_fixed_point x) +{ + if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */ + { + /* Obtain a 4 bit approximation */ + png_uint_32 e = png_32bit_exp[(x >> 12) & 0xf]; + + /* Incorporate the low 12 bits - these decrease the returned value by + * multiplying by a number less than 1 if the bit is set. The multiplier + * is determined by the above table and the shift. Notice that the values + * converge on 45426 and this is used to allow linear interpolation of the + * low bits. + */ + if (x & 0x800) + e -= (((e >> 16) * 44938U) + 16U) >> 5; + + if (x & 0x400) + e -= (((e >> 16) * 45181U) + 32U) >> 6; + + if (x & 0x200) + e -= (((e >> 16) * 45303U) + 64U) >> 7; + + if (x & 0x100) + e -= (((e >> 16) * 45365U) + 128U) >> 8; + + if (x & 0x080) + e -= (((e >> 16) * 45395U) + 256U) >> 9; + + if (x & 0x040) + e -= (((e >> 16) * 45410U) + 512U) >> 10; + + /* And handle the low 6 bits in a single block. */ + e -= (((e >> 16) * 355U * (x & 0x3fU)) + 256U) >> 9; + + /* Handle the upper bits of x. */ + e >>= x >> 16; + return e; + } + + /* Check for overflow */ + if (x <= 0) + return png_32bit_exp[0]; + + /* Else underflow */ + return 0; +} + +static png_byte +png_exp8bit(png_fixed_point lg2) +{ + /* Get a 32 bit value: */ + png_uint_32 x = png_exp(lg2); + + /* Convert the 32 bit value to 0..255 by multiplying by 256-1, note that the + * second, rounding, step can't overflow because of the first, subtraction, + * step. + */ + x -= x >> 8; + return (png_byte)((x + 0x7fffffU) >> 24); +} + +static png_uint_16 +png_exp16bit(png_fixed_point lg2) +{ + /* Get a 32 bit value: */ + png_uint_32 x = png_exp(lg2); + + /* Convert the 32 bit value to 0..65535 by multiplying by 65536-1: */ + x -= x >> 16; + return (png_uint_16)((x + 32767U) >> 16); +} +#endif /* FLOATING_ARITHMETIC */ + +png_byte +png_gamma_8bit_correct(unsigned int value, png_fixed_point gamma_val) +{ + if (value > 0 && value < 255) + { +# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED + double r = floor(255*pow(value/255.,gamma_val*.00001)+.5); + return (png_byte)r; +# else + png_int_32 lg2 = png_log8bit(value); + png_fixed_point res; + + if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1)) + return png_exp8bit(res); + + /* Overflow. */ + value = 0; +# endif + } + + return (png_byte)value; +} + +png_uint_16 +png_gamma_16bit_correct(unsigned int value, png_fixed_point gamma_val) +{ + if (value > 0 && value < 65535) + { +# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED + double r = floor(65535*pow(value/65535.,gamma_val*.00001)+.5); + return (png_uint_16)r; +# else + png_int_32 lg2 = png_log16bit(value); + png_fixed_point res; + + if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1)) + return png_exp16bit(res); + + /* Overflow. */ + value = 0; +# endif + } + + return (png_uint_16)value; +} + +/* This does the right thing based on the bit_depth field of the + * png_struct, interpreting values as 8 or 16 bit. While the result + * is nominally a 16 bit value if bit depth is 8 then the result is + * 8 bit (as are the arguments.) + */ +png_uint_16 /* PRIVATE */ +png_gamma_correct(png_structp png_ptr, unsigned int value, + png_fixed_point gamma_val) +{ + if (png_ptr->bit_depth == 8) + return png_gamma_8bit_correct(value, gamma_val); + + else + return png_gamma_16bit_correct(value, gamma_val); +} + +/* This is the shared test on whether a gamma value is 'significant' - whether + * it is worth doing gamma correction. + */ +int /* PRIVATE */ +png_gamma_significant(png_fixed_point gamma_val) +{ + return gamma_val < PNG_FP_1 - PNG_GAMMA_THRESHOLD_FIXED || + gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED; +} + +/* Internal function to build a single 16 bit table - the table consists of + * 'num' 256 entry subtables, where 'num' is determined by 'shift' - the amount + * to shift the input values right (or 16-number_of_signifiant_bits). + * + * The caller is responsible for ensuring that the table gets cleaned up on + * png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument + * should be somewhere that will be cleaned. + */ +static void +png_build_16bit_table(png_structp png_ptr, png_uint_16pp *ptable, + PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val) +{ + /* Various values derived from 'shift': */ + PNG_CONST unsigned int num = 1U << (8U - shift); + PNG_CONST unsigned int max = (1U << (16U - shift))-1U; + PNG_CONST unsigned int max_by_2 = 1U << (15U-shift); + unsigned int i; + + png_uint_16pp table = *ptable = + (png_uint_16pp)png_calloc(png_ptr, num * png_sizeof(png_uint_16p)); + + for (i = 0; i < num; i++) + { + png_uint_16p sub_table = table[i] = + (png_uint_16p)png_malloc(png_ptr, 256 * png_sizeof(png_uint_16)); + + /* The 'threshold' test is repeated here because it can arise for one of + * the 16 bit tables even if the others don't hit it. + */ + if (png_gamma_significant(gamma_val)) + { + /* The old code would overflow at the end and this would cause the + * 'pow' function to return a result >1, resulting in an + * arithmetic error. This code follows the spec exactly; ig is + * the recovered input sample, it always has 8-16 bits. + * + * We want input * 65535/max, rounded, the arithmetic fits in 32 + * bits (unsigned) so long as max <= 32767. + */ + unsigned int j; + for (j = 0; j < 256; j++) + { + png_uint_32 ig = (j << (8-shift)) + i; +# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED + /* Inline the 'max' scaling operation: */ + double d = floor(65535*pow(ig/(double)max, gamma_val*.00001)+.5); + sub_table[j] = (png_uint_16)d; +# else + if (shift) + ig = (ig * 65535U + max_by_2)/max; + + sub_table[j] = png_gamma_16bit_correct(ig, gamma_val); +# endif + } + } + else + { + /* We must still build a table, but do it the fast way. */ + unsigned int j; + + for (j = 0; j < 256; j++) + { + png_uint_32 ig = (j << (8-shift)) + i; + + if (shift) + ig = (ig * 65535U + max_by_2)/max; + + sub_table[j] = (png_uint_16)ig; + } + } + } +} + +/* NOTE: this function expects the *inverse* of the overall gamma transformation + * required. + */ +static void +png_build_16to8_table(png_structp png_ptr, png_uint_16pp *ptable, + PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val) +{ + PNG_CONST unsigned int num = 1U << (8U - shift); + PNG_CONST unsigned int max = (1U << (16U - shift))-1U; + unsigned int i; + png_uint_32 last; + + png_uint_16pp table = *ptable = + (png_uint_16pp)png_calloc(png_ptr, num * png_sizeof(png_uint_16p)); + + /* 'num' is the number of tables and also the number of low bits of low + * bits of the input 16 bit value used to select a table. Each table is + * itself index by the high 8 bits of the value. + */ + for (i = 0; i < num; i++) + table[i] = (png_uint_16p)png_malloc(png_ptr, + 256 * png_sizeof(png_uint_16)); + + /* 'gamma_val' is set to the reciprocal of the value calculated above, so + * pow(out,g) is an *input* value. 'last' is the last input value set. + * + * In the loop 'i' is used to find output values. Since the output is 8 + * bit there are only 256 possible values. The tables are set up to + * select the closest possible output value for each input by finding + * the input value at the boundary between each pair of output values + * and filling the table up to that boundary with the lower output + * value. + * + * The boundary values are 0.5,1.5..253.5,254.5. Since these are 9 bit + * values the code below uses a 16 bit value in i; the values start at + * 128.5 (for 0.5) and step by 257, for a total of 254 values (the last + * entries are filled with 255). Start i at 128 and fill all 'last' + * table entries <= 'max' + */ + last = 0; + for (i = 0; i < 255; ++i) /* 8 bit output value */ + { + /* Find the corresponding maximum input value */ + png_uint_16 out = (png_uint_16)(i * 257U); /* 16 bit output value */ + + /* Find the boundary value in 16 bits: */ + png_uint_32 bound = png_gamma_16bit_correct(out+128U, gamma_val); + + /* Adjust (round) to (16-shift) bits: */ + bound = (bound * max + 32768U)/65535U + 1U; + + while (last < bound) + { + table[last & (0xffU >> shift)][last >> (8U - shift)] = out; + last++; + } + } + + /* And fill in the final entries. */ + while (last < (num << 8)) + { + table[last & (0xff >> shift)][last >> (8U - shift)] = 65535U; + last++; + } +} + +/* Build a single 8 bit table: same as the 16 bit case but much simpler (and + * typically much faster). Note that libpng currently does no sBIT processing + * (apparently contrary to the spec) so a 256 entry table is always generated. + */ +static void +png_build_8bit_table(png_structp png_ptr, png_bytepp ptable, + PNG_CONST png_fixed_point gamma_val) +{ + unsigned int i; + png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256); + + if (png_gamma_significant(gamma_val)) for (i=0; i<256; i++) + table[i] = png_gamma_8bit_correct(i, gamma_val); + + else for (i=0; i<256; ++i) + table[i] = (png_byte)i; +} + +/* We build the 8- or 16-bit gamma tables here. Note that for 16-bit + * tables, we don't make a full table if we are reducing to 8-bit in + * the future. Note also how the gamma_16 tables are segmented so that + * we don't need to allocate > 64K chunks for a full 16-bit table. + */ +void /* PRIVATE */ +png_build_gamma_table(png_structp png_ptr, int bit_depth) +{ + png_debug(1, "in png_build_gamma_table"); + + if (bit_depth <= 8) + { + png_build_8bit_table(png_ptr, &png_ptr->gamma_table, + png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->gamma, + png_ptr->screen_gamma) : PNG_FP_1); + +#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \ + defined(PNG_READ_RGB_TO_GRAY_SUPPORTED) + if (png_ptr->transformations & ((PNG_BACKGROUND) | PNG_RGB_TO_GRAY)) + { + png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1, + png_reciprocal(png_ptr->gamma)); + + png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1, + png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) : + png_ptr->gamma/* Probably doing rgb_to_gray */); + } +#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_RGB_TO_GRAY_SUPPORTED */ + } + else + { + png_byte shift, sig_bit; + + if (png_ptr->color_type & PNG_COLOR_MASK_COLOR) + { + sig_bit = png_ptr->sig_bit.red; + + if (png_ptr->sig_bit.green > sig_bit) + sig_bit = png_ptr->sig_bit.green; + + if (png_ptr->sig_bit.blue > sig_bit) + sig_bit = png_ptr->sig_bit.blue; + } + else + sig_bit = png_ptr->sig_bit.gray; + + /* 16 bit gamma code uses this equation: + * + * ov = table[(iv & 0xff) >> gamma_shift][iv >> 8] + * + * Where 'iv' is the input color value and 'ov' is the output value - + * pow(iv, gamma). + * + * Thus the gamma table consists of up to 256 256 entry tables. The table + * is selected by the (8-gamma_shift) most significant of the low 8 bits of + * the color value then indexed by the upper 8 bits: + * + * table[low bits][high 8 bits] + * + * So the table 'n' corresponds to all those 'iv' of: + * + * <all high 8 bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1> + * + */ + if (sig_bit > 0 && sig_bit < 16U) + shift = (png_byte)(16U - sig_bit); /* shift == insignificant bits */ + + else + shift = 0; /* keep all 16 bits */ + + if (png_ptr->transformations & PNG_16_TO_8) + { + /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively + * the significant bits in the *input* when the output will + * eventually be 8 bits. By default it is 11. + */ + if (shift < (16U - PNG_MAX_GAMMA_8)) + shift = (16U - PNG_MAX_GAMMA_8); + } + + if (shift > 8U) + shift = 8U; /* Guarantees at least one table! */ + + png_ptr->gamma_shift = shift; + +#ifdef PNG_16BIT_SUPPORTED + if (png_ptr->transformations & (PNG_16_TO_8 | PNG_BACKGROUND)) +#endif + png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift, + png_ptr->screen_gamma > 0 ? png_product2(png_ptr->gamma, + png_ptr->screen_gamma) : PNG_FP_1); + +#ifdef PNG_16BIT_SUPPORTED + else + png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift, + png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->gamma, + png_ptr->screen_gamma) : PNG_FP_1); +#endif + +#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \ + defined(PNG_READ_RGB_TO_GRAY_SUPPORTED) + if (png_ptr->transformations & (PNG_BACKGROUND | PNG_RGB_TO_GRAY)) + { + png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift, + png_reciprocal(png_ptr->gamma)); + + /* Notice that the '16 from 1' table should be full precision, however + * the lookup on this table still uses gamma_shift, so it can't be. + * TODO: fix this. + */ + png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift, + png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) : + png_ptr->gamma/* Probably doing rgb_to_gray */); + } +#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_RGB_TO_GRAY_SUPPORTED */ + } +} +#endif /* READ_GAMMA */ +#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */ |