cgifsave: allow to apply maxerror optimization to frames with alpha channel #2778
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This looks great @dloebl, let's merge. Thank you for doing this, and sorry it took me a while :( I think the asan failure is a temporary clang issue. |
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As of now, the
maxerrorparameter cannot be applied to animated GIFs with an active alpha channel.Make it possible to detect cases where the alpha channel component of the current frame matches with the one from the frame before.
In these cases it is possible to use the transparency index for the
maxerroroptimization instead of for the alpha channel.This pull request helps to further improve the file size of animated GIFs (for reference: #2576).
Example:
$ vips copy test.gif[n=-1] old.gif[maxerror=16]$ vips copy test.gif[n=-1] new.gif[maxerror=16]$ gifsicle -O3 test.gif -o gifsicle.gifResults:
du -h *.gif1.0M new.gif5.8M gifsicle.gif6.1M test.gif9.8M old.gif