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google / zopfli

Zopfli Compression Algorithm is a compression library programmed in C to perform very good, but slow, deflate or zlib compression.
Apache License 2.0
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why zopflipng use the RGA of last color(alpha == 0) during LossyOptimizeTransparent #47

Open GoogleCodeExporter opened 9 years ago

GoogleCodeExporter commented 9 years ago 
Seems it's smaller when use RGBA all 0.

Original issue reported on code.google.com by yyjdel...@gmail.com on 19 Dec 2014 at 6:11

frkay commented 9 years ago

The alpha cleaning performed by zopflipng has been analyzed here: http://encode.ru/threads/1717-ZopfliPNG?p=33102&viewfull=1#post33102

You can now try different ways to clean alpha (what cryopng did) inside zopflipng: http://encode.ru/threads/1260-CryoPNG-short-introduction use the new option --alpha_cleaner to try different cleaning methods (based on reversed PNG filtering)