Yeah, it almost looks like a premultiply issue, but PNG should be non-premultipl... | Hacker News

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		berkut on June 27, 2012 \| parent \| context \| favorite \| on: TinyPNG: Lossy compression for PNG that preserves ... Yeah, it almost looks like a premultiply issue, but PNG should be non-premultiplied, so... http://imgur.com/6ovIu Also, the original has values in the RGB channels for pixels with no alpha that aren't visible (due to the alpha) but need to be compressed, so it's not a fair test (although both do to some degree - turquoise area around the bear), so the new one could be compressed even more.

pornel on June 27, 2012 [–]

pngquant backing this service works in premultiplied RGBA colorspace (but with 32-bit floating point per gun).

However the distortion is merely a side-effect of reducing image to 256-colors (from 15k colors).

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