Colours with a saturation of zero (Greys) have no hue value (stored as RGB). When increasing the saturation of such colours, "saturation" layer blend mode assumes they have a hue of zero, i.e. red.
I'm assuming using a HSV or HSL colour profile might avoid this (by having a redundant hue value even when saturation is zero), but I haven't found any such profiles to test. Note that increasing saturation using the hue-saturation tool does not give the same result: white remains white, grey remains grey. I would regard the saturation layer blend mode's result as unexpected behaviour for the following reasons: - Making assumption of non-existent hue data. - Not useful to end user. Controlling the saturation of parts of an image via a saturation layer doesn't work if the image contains any white (or grey) pixels. For example, an image of a green apple with white highlights will end up as a green apple with red or pink highlights. (With discontinuity being introduced as very pale green suddenly reaches pure white) - Behaviour different from tool with same name. Regards, Tom _______________________________________________ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
