[account42]

zopflipng typically beats pngcrus and optipng (on Linux at least) but by default it drops auxillary PNG chunks [0] which can result in browsers (and other applications) using a different color space, causing the resulting images to look more washed out than the original. To prevent this you need to explicitly pass --keepchunks=cHRM,gAMA,pHYs,iCCP,sRGB,oFFs,sTER to zopflipng.

cwebp seems to have a simmilar issue when starting with png files. Sucks that color space support is still so inconsistent.

Unfortunately zopflipng (and most other tools) don't have APNG support, keeping only the first frame :|

[0] https://github.com/google/zopfli/issues/113