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R.L. Dane :Debian: :OpenBSD: :FreeBSD: 🍵 :MiraLovesYou:

If anyone's curious why I'm always doing the little #LossyPNG dance, it's because you can get some crazy good compression sacrificing color depth, instead of using a traditional lossy algorithm which gives you good compression by sacrificing detail:

tmp $ ll kate*
-rw-rw-r-- 1 rld rld 124,117 Feb 23 12:51 kate-kwrite1.png
-rw-rw-r-- 1 rld rld 23,710 Feb 23 12:51 kate-kwrite2.png
-rw-rw-r-- 1 rld rld 19,936 Feb 23 12:54 kate-kwrite3.png
-rw-rw-r-- 1 rld rld 18,572 Feb 23 12:55 kate-kwrite4.png
186335 total
tmp $ colors kate*
kate-kwrite1.png (unknown)
kate-kwrite2.png 16
kate-kwrite3.png 9
kate-kwrite4.png 8

(kate-kwrite1.png was the original (truecolor) screenshot)
(kate-kwrite2.png was automatically reduced to 16 colors by ImageMagic)
(kate-kwrite3.png was reduced to 9 colors by hand-picking dominant colors in GIMP)
(kate-kwrite4.png was reduced to 8 colors by hand-picking dominant colors in GIMP)

𝖆𝖒𝖆𝖗𝖔𝖐

@amarok@mastodonczech.cz · 3 days ago

@rl_dane
Or just use https://tinypng.com/
It's much faster :)

R.L. Dane :Debian: :OpenBSD: :FreeBSD: 🍵 :MiraLovesYou:

@rl_dane@polymaths.social · 3 days ago

@amarok

That dropped it down to 46KB, which is impressive, especially since it reduced it to 256 colors in a way that's not noticeable, but I can get much smaller sizes by reducing the colors even further.

I do wonder what else it's doing, as it gets better compression than imagemagick does when reducing to 256 colors:

124,117 original
23,710 ImageMagick 16 colors
19,936 GIMP 9 colors
18,572 GIMP 8 colors
40,803 ImageMagick 64 colors
51,271 ImageMagick 256 colors
46,918 tinypng.com

R.L. Dane :Debian: :OpenBSD: :FreeBSD: 🍵 :MiraLovesYou:

@rl_dane@polymaths.social · 3 days ago

@amarok

I did some more testing. I tried using GIMP to reduce to 256 colors using all four of their dithering options (none, ordered, floyd-steinberg, floyd-steinberg reduced color bleeding)

The only dithering options in GIMP that produced a smaller image was none and ordered, so that website has some kind of secret sauce that makes it a little better than GIMP, but I can still get it smaller with a little elbow grease. ;)

𝖆𝖒𝖆𝖗𝖔𝖐

@amarok@mastodonczech.cz · 3 days ago

@rl_dane
I use TinyPNG just to save time, it's fast and gives good results. You can even squeeze a few more percent when feeding TinyPNG with the result again. But I would prefer GIMP and other tools if I wanted perfect control over the palette, so I agree with you.

R.L. Dane :Debian: :OpenBSD: :FreeBSD: 🍵 :MiraLovesYou:

@rl_dane@polymaths.social · 3 days ago

@amarok

Just FYI, I was able to get within 4.1% of the size of TinyPNG (and close to the same quality) just using:

convert input.png -colors 256 output.png

You just need imagemagick installed and Bob's your uncle. ;)

You can even script/batch it. It's pretty cool. GIMP gives better results, of course, but imagmagick is crazy convenient.

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