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Diffstat (limited to 'src/3rdparty/libpng/libpng-manual.txt')
| -rw-r--r-- | src/3rdparty/libpng/libpng-manual.txt | 157 |
1 files changed, 51 insertions, 106 deletions
diff --git a/src/3rdparty/libpng/libpng-manual.txt b/src/3rdparty/libpng/libpng-manual.txt index d4407ef2ea..19cfed28ad 100644 --- a/src/3rdparty/libpng/libpng-manual.txt +++ b/src/3rdparty/libpng/libpng-manual.txt @@ -1,9 +1,7 @@ libpng-manual.txt - A description on how to use and modify libpng - libpng version 1.6.34 - September 29, 2017 - Updated and distributed by Glenn Randers-Pehrson - <glennrp at users.sourceforge.net> - Copyright (c) 1998-2017 Glenn Randers-Pehrson + Copyright (c) 2018 Cosmin Truta + Copyright (c) 1998-2018 Glenn Randers-Pehrson This document is released under the libpng license. For conditions of distribution and use, see the disclaimer @@ -11,9 +9,13 @@ libpng-manual.txt - A description on how to use and modify libpng Based on: - libpng versions 0.97, January 1998, through 1.6.34 - September 29, 2017 + libpng version 1.6.36 - December 1, 2018 + Updated and distributed by Cosmin Truta + Copyright (c) 2018 Cosmin Truta + + libpng versions 0.97, January 1998, through 1.6.35 - July 15, 2018 Updated and distributed by Glenn Randers-Pehrson - Copyright (c) 1998-2017 Glenn Randers-Pehrson + Copyright (c) 1998-2018 Glenn Randers-Pehrson libpng 1.0 beta 6 - version 0.96 - May 28, 1997 Updated and distributed by Andreas Dilger @@ -45,7 +47,6 @@ libpng-manual.txt - A description on how to use and modify libpng XIII. Detecting libpng XIV. Source code repository XV. Coding style - XVI. Y2K Compliance in libpng I. Introduction @@ -66,7 +67,7 @@ file format in application programs. The PNG specification (second edition), November 2003, is available as a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2004 (E)) at -<https://www.w3.org/TR/2003/REC-PNG-20031110/ +<https://www.w3.org/TR/2003/REC-PNG-20031110/>. The W3C and ISO documents have identical technical content. The PNG-1.2 specification is available at @@ -74,9 +75,9 @@ The PNG-1.2 specification is available at It is technically equivalent to the PNG specification (second edition) but has some additional material. -The PNG-1.0 specification is available as RFC 2083 +The PNG-1.0 specification is available as RFC 2083 at <https://png-mng.sourceforge.io/pub/png/spec/1.0/> and as a -W3C Recommendation <https://www.w3.org/TR/REC-png-961001>. +W3C Recommendation at <https://www.w3.org/TR/REC-png-961001>. Some additional chunks are described in the special-purpose public chunks documents at <http://www.libpng.org/pub/png/spec/register/> @@ -348,18 +349,18 @@ Customizing libpng. FILE *fp = fopen(file_name, "rb"); if (!fp) { - return (ERROR); + return ERROR; } if (fread(header, 1, number, fp) != number) { - return (ERROR); + return ERROR; } is_png = !png_sig_cmp(header, 0, number); if (!is_png) { - return (NOT_PNG); + return NOT_PNG; } Next, png_struct and png_info need to be allocated and initialized. In @@ -378,7 +379,7 @@ create the structure, so your application should check for that. user_error_fn, user_warning_fn); if (!png_ptr) - return (ERROR); + return ERROR; png_infop info_ptr = png_create_info_struct(png_ptr); @@ -386,7 +387,7 @@ create the structure, so your application should check for that. { png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL); - return (ERROR); + return ERROR; } If you want to use your own memory allocation routines, @@ -421,7 +422,7 @@ free any memory. png_destroy_read_struct(&png_ptr, &info_ptr, &end_info); fclose(fp); - return (ERROR); + return ERROR; } Pass (png_infopp)NULL instead of &end_info if you didn't create @@ -503,7 +504,7 @@ input stream. You must supply the function png_byte name[5]; png_byte *data; - png_size_t size; + size_t size; /* Note that libpng has already taken care of the CRC handling */ @@ -512,9 +513,9 @@ input stream. You must supply the function unknown chunk structure, process it, and return one of the following: */ - return (-n); /* chunk had an error */ - return (0); /* did not recognize */ - return (n); /* success */ + return -n; /* chunk had an error */ + return 0; /* did not recognize */ + return n; /* success */ } (You can give your function another name that you like instead of @@ -1003,7 +1004,7 @@ chunks to be assumed to be encoded using sRGB. png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC); In this case the output is assumed to be something like an sRGB conformant -display preceeded by a power-law lookup table of power 1.45. This is how +display preceded by a power-law lookup table of power 1.45. This is how early Mac systems behaved. png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_GAMMA_LINEAR); @@ -1055,7 +1056,7 @@ faster.) When the default gamma of PNG files doesn't match the output gamma. If you have PNG files with no gamma information png_set_alpha_mode allows -you to provide a default gamma, but it also sets the ouput gamma to the +you to provide a default gamma, but it also sets the output gamma to the matching value. If you know your PNG files have a gamma that doesn't match the output you can take advantage of the fact that png_set_alpha_mode always sets the output gamma but only sets the PNG @@ -2409,7 +2410,7 @@ separate. { png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); - return (ERROR); + return ERROR; } png_read_end(png_ptr, end_info); @@ -2549,7 +2550,7 @@ png_infop info_ptr; user_error_fn, user_warning_fn); if (!png_ptr) - return (ERROR); + return ERROR; info_ptr = png_create_info_struct(png_ptr); @@ -2557,14 +2558,14 @@ png_infop info_ptr; { png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL); - return (ERROR); + return ERROR; } if (setjmp(png_jmpbuf(png_ptr))) { png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); - return (ERROR); + return ERROR; } /* This one's new. You can provide functions @@ -2598,7 +2599,7 @@ png_infop 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 @@ -2742,7 +2743,7 @@ custom writing functions. See the discussion under Customizing libpng. FILE *fp = fopen(file_name, "wb"); if (!fp) - return (ERROR); + 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 @@ -2757,14 +2758,14 @@ both "png_ptr"; you can call them anything you like, such as 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_write_struct(&png_ptr, (png_infopp)NULL); - return (ERROR); + return ERROR; } If you want to use your own memory allocation routines, @@ -2791,7 +2792,7 @@ section below for more information on the libpng error handling. { png_destroy_write_struct(&png_ptr, &info_ptr); fclose(fp); - return (ERROR); + return ERROR; } ... return; @@ -3779,7 +3780,7 @@ in-memory bitmap formats or to be written from the same formats. If these formats do not accommodate your needs then you can, and should, use the more sophisticated APIs above - these support a wide variety of in-memory formats and a wide variety of sophisticated transformations to those formats as well -as a wide variety of APIs to manipulate ancilliary information. +as a wide variety of APIs to manipulate ancillary information. To read a PNG file using the simplified API: @@ -4055,7 +4056,7 @@ Flags containing additional information about the image are held in the 'flags' field of png_image. PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB == 0x01 - This indicates the the RGB values of the in-memory bitmap do not + This indicates that the RGB values of the in-memory bitmap do not correspond to the red, green and blue end-points defined by sRGB. PNG_IMAGE_FLAG_FAST == 0x02 @@ -4102,7 +4103,7 @@ READ APIs The PNG header is read from the stdio FILE object. int png_image_begin_read_from_memory(png_imagep image, - png_const_voidp memory, png_size_t size) + png_const_voidp memory, size_t size) The PNG header is read from the given memory buffer. @@ -4255,10 +4256,10 @@ png_get_io_ptr(). For example: 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); + png_bytep data, size_t length); void user_write_data(png_structp png_ptr, - png_bytep data, png_size_t length); + png_bytep data, size_t length); void user_flush_data(png_structp png_ptr); @@ -4521,7 +4522,7 @@ When PNG_DEBUG = 1, the macros are defined, but only png_debug statements having level = 0 will be printed. There aren't any such statements in this version of libpng, but if you insert some they will be printed. -VII. MNG support +VII. MNG support The MNG specification (available at http://www.libpng.org/pub/mng) allows certain extensions to PNG for PNG images that are embedded in MNG datastreams. @@ -4548,7 +4549,7 @@ or any other MNG chunks; your application must provide its own support for them. You may wish to consider using libmng (available at https://www.libmng.com/) instead. -VIII. Changes to Libpng from version 0.88 +VIII. Changes to Libpng from version 0.88 It should be noted that versions of libpng later than 0.96 are not distributed by the original libpng author, Guy Schalnat, nor by @@ -4603,7 +4604,7 @@ application: png_uint_32 application_vn = PNG_LIBPNG_VER; -IX. Changes to Libpng from version 1.0.x to 1.2.x +IX. Changes to Libpng from version 1.0.x to 1.2.x Support for user memory management was enabled by default. To accomplish this, the functions png_create_read_struct_2(), @@ -4700,7 +4701,7 @@ which also expands tRNS to alpha was replaced with png_set_expand_gray_1_2_4_to_8() which does not. It has been deprecated since libpng-1.0.18 and 1.2.9. -X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x +X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x Private libpng prototypes and macro definitions were moved from png.h and pngconf.h into a new pngpriv.h header file. @@ -4784,7 +4785,7 @@ behavior in case the application runs out of memory part-way through the process. We changed the prototypes of png_get_compression_buffer_size() and -png_set_compression_buffer_size() to work with png_size_t instead of +png_set_compression_buffer_size() to work with size_t instead of png_uint_32. Support for numbered error messages was removed by default, since we @@ -4810,7 +4811,7 @@ was renamed to PNG_READ_QUANTIZE_SUPPORTED. We removed the trailing '.' from the warning and error messages. -XI. Changes to Libpng from version 1.4.x to 1.5.x +XI. 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. @@ -4873,7 +4874,7 @@ 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. +declare these arguments with 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 @@ -5068,7 +5069,7 @@ 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.) -XII. Changes to Libpng from version 1.5.x to 1.6.x +XII. Changes to Libpng from version 1.5.x to 1.6.x A "simplified API" has been added (see documentation in png.h and a simple example in contrib/examples/pngtopng.c). The new publicly visible API @@ -5231,7 +5232,7 @@ attempt to decode the Exif profile; it simply returns a byte array containing the profile to the calling application which must do its own decoding. -XIII. Detecting libpng +XIII. 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 @@ -5255,9 +5256,8 @@ or you can browse it with a web browser at https://github.com/glennrp/libpng or https://sourceforge.net/p/libpng/code/ci/libpng16/tree/ -Patches can be sent to glennrp at users.sourceforge.net or to -png-mng-implement at lists.sourceforge.net or you can upload them to -the libpng bug tracker at +Patches can be sent to png-mng-implement at lists.sourceforge.net or +uploaded to the libpng bug tracker at https://libpng.sourceforge.io/ @@ -5266,9 +5266,9 @@ or as a "pull request" to https://github.com/glennrp/libpng/pulls We also accept patches built from the tar or zip distributions, and -simple verbal discriptions of bug fixes, reported either to the +simple verbal descriptions of bug fixes, reported either to the SourceForge bug tracker, to the png-mng-implement at lists.sf.net -mailing list, as github issues, or directly to glennrp. +mailing list, as github issues. XV. Coding style @@ -5289,7 +5289,7 @@ braces on separate lines: The braces can be omitted from simple one-line actions: if (condition) - return (0); + return 0; We use 3-space indentation, except for continued statements which are usually indented the same as the first line of the statement @@ -5407,58 +5407,3 @@ We do not use the TAB character for indentation in the C sources. Lines do not exceed 80 characters. Other rules can be inferred by inspecting the libpng source. - -XVI. Y2K Compliance in libpng - -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 1.6.34 are Y2K compliant. It is my belief that earlier -versions were also Y2K compliant. - -Libpng only has two year fields. One is a 2-byte unsigned integer -that will hold years up to 65535. The other, which is deprecated, -holds the date in text format, and will hold years up to 9999. - -The integer is - "png_uint_16 year" in png_time_struct. - -The string is - "char time_buffer[29]" in png_struct. This is no longer used -in libpng-1.6.x and will be removed from libpng-1.7.0. - -There are seven time-related functions: - - png_convert_to_rfc_1123_buffer() in png.c - (formerly png_convert_to_rfc_1152() in error, and - also formerly png_convert_to_rfc_1123()) - png_convert_from_struct_tm() in pngwrite.c, called - in pngwrite.c - png_convert_from_time_t() in pngwrite.c - png_get_tIME() in pngget.c - png_handle_tIME() in pngrutil.c, called in pngread.c - png_set_tIME() in pngset.c - png_write_tIME() in pngwutil.c, called in pngwrite.c - -All appear to handle dates properly in a Y2K environment. The -png_convert_from_time_t() function calls gmtime() to convert from system -clock time, which returns (year - 1900), which we properly convert to -the full 4-digit year. There is a possibility that applications using -libpng are not passing 4-digit years into the png_convert_to_rfc_1123() -function, or that they are incorrectly passing only a 2-digit year -instead of "year - 1900" into the png_convert_from_struct_tm() function, -but this is not under our control. The libpng documentation has always -stated that it works with 4-digit years, and the APIs have been -documented as such. - -The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned -integer to hold the year, and can hold years as large as 65535. - -zlib, upon which libpng depends, is also Y2K compliant. It contains -no date-related code. - - - Glenn Randers-Pehrson - libpng maintainer - PNG Development Group |