diff options
author | John Bowler <jbowler@acm.org> | 2012-08-15 22:53:00 -0500 |
---|---|---|
committer | Glenn Randers-Pehrson <glennrp at users.sourceforge.net> | 2012-08-15 22:53:00 -0500 |
commit | e9567514dd42a4a756def1f21d3b52ea83966777 (patch) | |
tree | 3483dc7bbcccef34253fae94a0b6439988d4e591 /pngwrite.c | |
parent | b593b3f0353fa039fc73347d1e63210538034a88 (diff) | |
download | libpng-e9567514dd42a4a756def1f21d3b52ea83966777.tar.gz |
[libpng16] Unknown handling fixes and clean up. This adds more correct option
control of the unknown handling, corrects the pre-existing bug where
the per-chunk 'keep' setting is ignored and makes it possible to skip
IDAT chunks in the sequential reader (broken in earlier 1.6 versions).
There is a new test program, test-unknown.c, which is a work in progress
(not currently part of the test suite). Comments in the header files now
explain how the unknown handling works.
Diffstat (limited to 'pngwrite.c')
-rw-r--r-- | pngwrite.c | 131 |
1 files changed, 57 insertions, 74 deletions
diff --git a/pngwrite.c b/pngwrite.c index 0c2bed57d..098a68230 100644 --- a/pngwrite.c +++ b/pngwrite.c @@ -18,6 +18,54 @@ #ifdef PNG_WRITE_SUPPORTED +#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED +/* Write out all the unknown chunks for the current given location */ +static void +write_unknown_chunks(png_structrp png_ptr, png_const_inforp info_ptr, + unsigned int where) +{ + if (info_ptr->unknown_chunks_num) + { + png_const_unknown_chunkp up; + + png_debug(5, "writing extra chunks"); + + for (up = info_ptr->unknown_chunks; + up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num; + ++up) + if (up->location & where) + { + int keep = png_handle_as_unknown(png_ptr, up->name); + + /* NOTE: this code is radically different from the read side in the + * matter of handling an ancilliary unknown chunk. In the read side + * the default behavior is to discard it, in the code below the default + * behavior is to write it. Critical chunks are, however, only + * written if explicitly listed or if the default is set to write all + * unknown chunks. + * + * The default handling is also slightly weird - it is not possible to + * stop the writing of all unsafe-to-copy chunks! + * + * TODO: REVIEW: this would seem to be a bug. + */ + if (keep != PNG_HANDLE_CHUNK_NEVER && + ((up->name[3] & 0x20) /* safe-to-copy overrides everything */ || + keep == PNG_HANDLE_CHUNK_ALWAYS || + (keep == PNG_HANDLE_CHUNK_AS_DEFAULT && + png_ptr->unknown_default == PNG_HANDLE_CHUNK_ALWAYS))) + { + /* TODO: review, what is wrong with a zero length unknown chunk? */ + if (up->size == 0) + png_warning(png_ptr, "Writing zero-length unknown chunk"); + + png_write_chunk(png_ptr, up->name, up->data, up->size); + } + } + } +} +#endif /* PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED */ + /* Writes all the PNG information. This is the suggested way to use the * library. If you have a new chunk to add, make a function to write it, * and put it in the correct location here. If you want the chunk written @@ -54,10 +102,12 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr) info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type, info_ptr->filter_type, #ifdef PNG_WRITE_INTERLACING_SUPPORTED - info_ptr->interlace_type); + info_ptr->interlace_type #else - 0); + 0 #endif + ); + /* The rest of these check to see if the valid field has the appropriate * flag set, and if it does, writes the chunk. * @@ -125,34 +175,9 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr) #endif #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED - if (info_ptr->unknown_chunks_num) - { - png_unknown_chunk *up; - - png_debug(5, "writing extra chunks"); - - for (up = info_ptr->unknown_chunks; - up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num; - up++) - { - int keep = png_handle_as_unknown(png_ptr, up->name); - - if (keep != PNG_HANDLE_CHUNK_NEVER && - up->location && - !(up->location & PNG_HAVE_PLTE) && - !(up->location & PNG_HAVE_IDAT) && - !(up->location & PNG_AFTER_IDAT) && - ((up->name[3] & 0x20) || keep == PNG_HANDLE_CHUNK_ALWAYS || - (png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS))) - { - if (up->size == 0) - png_warning(png_ptr, "Writing zero-length unknown chunk"); - - png_write_chunk(png_ptr, up->name, up->data, up->size); - } - } - } + write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR); #endif + png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE; } } @@ -302,29 +327,7 @@ png_write_info(png_structrp png_ptr, png_const_inforp info_ptr) #endif /* tEXt */ #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED - if (info_ptr->unknown_chunks_num) - { - png_unknown_chunk *up; - - png_debug(5, "writing extra chunks"); - - for (up = info_ptr->unknown_chunks; - up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num; - up++) - { - int keep = png_handle_as_unknown(png_ptr, up->name); - if (keep != PNG_HANDLE_CHUNK_NEVER && - up->location && - (up->location & PNG_HAVE_PLTE) && - !(up->location & PNG_HAVE_IDAT) && - !(up->location & PNG_AFTER_IDAT) && - ((up->name[3] & 0x20) || keep == PNG_HANDLE_CHUNK_ALWAYS || - (png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS))) - { - png_write_chunk(png_ptr, up->name, up->data, up->size); - } - } - } + write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_PLTE); #endif } @@ -416,27 +419,7 @@ png_write_end(png_structrp png_ptr, png_inforp info_ptr) } #endif #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED - if (info_ptr->unknown_chunks_num) - { - png_unknown_chunk *up; - - png_debug(5, "writing extra chunks"); - - for (up = info_ptr->unknown_chunks; - up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num; - up++) - { - int keep = png_handle_as_unknown(png_ptr, up->name); - if (keep != PNG_HANDLE_CHUNK_NEVER && - up->location && - (up->location & PNG_AFTER_IDAT) && - ((up->name[3] & 0x20) || keep == PNG_HANDLE_CHUNK_ALWAYS || - (png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS))) - { - png_write_chunk(png_ptr, up->name, up->data, up->size); - } - } - } + write_unknown_chunks(png_ptr, info_ptr, PNG_AFTER_IDAT); #endif } @@ -889,7 +872,7 @@ png_write_destroy(png_structrp png_ptr) png_free(png_ptr, png_ptr->inv_filter_costs); #endif -#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED +#ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED png_free(png_ptr, png_ptr->chunk_list); #endif |