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The browser demo (https://scrtwpns.com/mixbox/painter/ https://scrtwpns.com/mixbox/painter/) "runs two color mixing implementations in parallel: one based on Mi

by nannal 5y ago

The browser demo (https://scrtwpns.com/mixbox/painter/ https://scrtwpns.com/mixbox/painter/) "runs two color mixing implementations in parallel: one based on Mixbox and the other that performs ordinary RGB mixing." The issue is clicking between "Mixbox" & "Normal" in the app with unmixed paint shows two different starting colours which must make any comparison of mixed colours effectively void.

jezeq 5y ago
The starting colors are actually identical. Try painting a 100% opaque color pool and then switch between Mixbox and Normal. You'll see that the colors are the same. The difference is their behavior in thinner layers - when the brush opacity is lower. When you spread dark pigments over a white canvas, they usually turn very radiant, saturated colors. Phthalo Blue turns from dark purplish blue into turquoise for example. RGB mixing doesn't handle those saturation gains and that's why a brush stroke made in the 'Normal' mode looks way more dull than the brush stroke made in 'Mixbox' mode with the identical starting color. This is actually an important point of pigment mixing. The saturation gains and hue shifts when pigments get spread or mixed with white are beautiful. RGB linear mixing (the 'normal' mode) doesn't capture them.
- raphlinus 5y ago
  This is correct, though I can certainly see how someone would come to the conclusion that starting colors are not identical, as default painting mode is less than full opacity, so the mixed color is generally a lot more saturated than plain sRGB. And a clarification, I wouldn't call this RGB linear mixing, to me that's mixing in a physical light intensity space. Rather, it's alpha compositing in an sRGB color space, which is probably the most common mode. It's possible to verify this by setting transparency to exactly 50%, painting 50% black over white, and 50% white over solid black, verifying that the color is the same, and measuring that - it's very close to sRGB (128, 128, 128). Linear mixing would give approximately (188, 188, 188). Incidentally, this also shows that Mixbox doesn't retain neutral hue when mixing black and white - it gives something closer to (129, 127, 130), a slight reddish-purplish tone compared with neutral gray.

by nannal 5y ago

jezeq 5y ago

The starting colors are actually identical. Try painting a 100% opaque color pool and then switch between Mixbox and Normal. You'll see that the colors are the same. The difference is their behavior in thinner layers - when the brush opacity is lower. When you spread dark pigments over a white canvas, they usually turn very radiant, saturated colors. Phthalo Blue turns from dark purplish blue into turquoise for example. RGB mixing doesn't handle those saturation gains and that's why a brush stroke made in the 'Normal' mode looks way more dull than the brush stroke made in 'Mixbox' mode with the identical starting color. This is actually an important point of pigment mixing. The saturation gains and hue shifts when pigments get spread or mixed with white are beautiful. RGB linear mixing (the 'normal' mode) doesn't capture them.

raphlinus 5y ago
This is correct, though I can certainly see how someone would come to the conclusion that starting colors are not identical, as default painting mode is less than full opacity, so the mixed color is generally a lot more saturated than plain sRGB. And a clarification, I wouldn't call this RGB linear mixing, to me that's mixing in a physical light intensity space. Rather, it's alpha compositing in an sRGB color space, which is probably the most common mode. It's possible to verify this by setting transparency to exactly 50%, painting 50% black over white, and 50% white over solid black, verifying that the color is the same, and measuring that - it's very close to sRGB (128, 128, 128). Linear mixing would give approximately (188, 188, 188). Incidentally, this also shows that Mixbox doesn't retain neutral hue when mixing black and white - it gives something closer to (129, 127, 130), a slight reddish-purplish tone compared with neutral gray.