Re: [LIBART] Cool demo, graphics bug

["k.wetzel" <k wetzel welfen-netz com>]

[...]
> > Cool.  What do the black lines represent ?  Does anybody know why
> > PNG gives such a poor compression rate on this image (only
> > about 1:4) ?
[...]
> The compression ratio is poor because Libart does its antialiasing
> analytically, so all gray values are represented. You can improve
> PNG compression by doing quantization prior to compression:

Yes, yet I thought even the original 24bit image would be compressed
better:
1 - large white areas (around 70% of the image)
2 - green and blue channels are similar
3 - only about 20,000 color values are used
4 - potentially the gradients lead to similar colors being closer

Using cues 1 (RLE), 2, and 4(delta-coding) gave me compression down to
< 20% but not the 10% I estimated by looking at the image :^>
(Using a better variable-length coder then I did, palettes/sliding
window, etc. may save some, though)

Best regards,
kai