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2ab4b72f53
This is a (minor) bitstream change: if the 'color_space' bit is set to '1' (which is normally an undefined/invalid behaviour), we add extra data at the end of partition #0 (so-called 'extensions') Namely, we add the size of the extension data as 3 bytes (little-endian), followed by a set of bits telling which extensions we're incorporating. The data then _preceeds_ this trailing tags. This is all experimental, and you'll need to have '#define WEBP_EXPERIMENTAL_FEATURES' in webp/types.h to enable this code (at your own risk! :)) Still, this hack produces almost-valid WebP file for decoders that don't check this color_space bit. In particular, previous 'dwebp' (and for instance Chrome) will recognize this files and decode them, but without the alpha of course. Other decoder will just see random extra stuff at the end of partition #0. To experiment with the alpha-channel, you need to compile on Unix platform and use PNGs for input/output. If 'alpha.png' is a source with alpha channel, then you can try (on Unix): cwebp alpha.png -o alpha.webp dwebp alpha.webp -o test.png cwebp now has a '-noalpha' flag to ignore any alpha information from the source, if present. More hacking and experimenting welcome! Change-Id: I3c7b1fd8411c9e7a9f77690e898479ad85c52f3e |
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| webp | ||
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| Makefile.am | ||