On 10/04/2010 04:17 AM, David Gowers (kampu) wrote:
> Try making a flat region of color #2a7e23, selecting Pencil tool,
> choosing Color mode and a large brush, and painting #11e500 repeatedly
> over the same area.
> In general, you can manifest this bug by picking a dark color,
> making a region of it, and painting over with a HSV value-increased
> version of same color.
> Ideally, this would possibly change Hue or Chromaticity, but shouldn't
> change Lightness significantly. Looking at the LCH color selector, L
> rises ~2 points for each paint application in my example.
Unfortunately, that's not fixable but a result of the too small gamut of
the sRGB working space.
Combining the lightness of #2a7e23 with hue/saturation of #11e500
results in (linear) sRGB values which are negative for red and blue.
Clipping those to 0-255 yields the result you observed (the color
becomes lighter than it should be).
Whenever you observe this misbehavior, at least one of the resulting RGB
components should be at 0 or 255 -- otherwise it really would be a bug.
The only fix is to use a larger working space, like scRGB.
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