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Diffstat (limited to 'README.zopflipng')
| -rw-r--r-- | README.zopflipng | 23 |
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diff --git a/README.zopflipng b/README.zopflipng index 84019ee..fc1ced4 100644 --- a/README.zopflipng +++ b/README.zopflipng @@ -12,8 +12,27 @@ ZopfliPNG is a command line program to optimize the Portable Network Graphics This is an alpha-release for testing while improvements, particularly to add palette selection, are still being made. Feedback and bug reports are welcome. -To build ZopfliPNG, use "make zopflipng", or compile all the sources except -zopfli_bin.c. +Important: + +This PNG optimizer removes ancillary chunks (pieces of metadata) from the +PNG image that normally do not affect rendering. However in special +circumstances you may wish to keep some. For example for a design using +custom gamma correction, keeping it may be desired. Visually check in the +target renderer after using ZopfliPNG. Use --keepchunks to keep chunks, e.g. +--keepchunks=gAMA,pHYs to keep gamma and DPI information. This will increase +file size. The following page contains a list of ancillary PNG chunks: +http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html + +Build instructions: + +To build ZopfliPNG, compile all .c, .cc and .cpp files from src/zopfli, +src/zopflipng and src/zopflipng/lodepng, except src/zopfli/zopfli_bin.c, to a +single binary with C++, e.g.: +g++ src/zopfli/{blocksplitter,cache,deflate,gzip_container,hash,katajainen,lz77,squeeze,tree,util,zlib_container,zopfli_lib}.c src/zopflipng/*.cc src/zopflipng/lodepng/*.cpp -O2 -W -Wall -Wextra -Wno-unused-function -ansi -pedantic -o zopflipng + +A makefile is provided as well, but only for linux: use "make zopflipng" with +the Zopfli makefile. For other platforms, please use the build instructions +above instead. The main compression algorithm in ZopfliPNG is ported from WebP lossless, but naturally cannot give as much compression gain for PNGs as it does for a more |