Treating alpha like RGB about libimagequant HOT 3 CLOSED

This is fundamentally impossible in libimagequant. It intentionally uses premultiplied alpha color space throughout the codebase. In this colorspace RGB and A are correlated, and are not independent channels.

Separating alpha would make PNG8 much lower quality and inefficient. Instead of reducing 16mln combinations, it'd have to work with 4 billion combinations, and visually invisible alpha combinations would take precious palette entries away from the visible RGB colors.

I suggest that you use two separate PNG files: RGB PNG8 for color, and a separate grayscale PNG for the alpha-but-not-really-alpha channel.

from libimagequant.

It looks like that's a special case for alpha = 0? I have been able to workaround that by forcing alpha to be at least 1, but would still prefer a cleaner solution!

from libimagequant.

@kornelski I see. Thanks. I'll look into those options.

from libimagequant.