Am 29.08.2015 um 21:54 schrieb Wolthera: > On Sat, Aug 29, 2015 at 7:42 PM, <marti.ma...@littlecms.com> wrote: >> Regarding the question on gamut, the "good" way to represent a gamut is by >> using a 3D solid, just because our vision have 3 cones that gives us three >> dimensions. The tonge chromaticity diagram can give an idea of the >> primaries, but does not explain how the gray axis affects the color.
> I know that, but right now a lot of artists already find the color > management terrifying, displaying a 3d gamut would be something I would > like postpone until the general krita-user community has gotten used to the > idea that colors have spaces. I've already had a lot of people freak out at > the notion of giving an explanation of what certain properties mean for a > profile, and this is outside the reactions we get on Krita having profiles > at all(after all, there's no need for anything besides a radio button box > with 'RGB' and 'CMYK' for proper artists according to these people). I > imagine giving people a 3d color gamut at this current stage will cause > heart-attacks. Still, it seems the same kind of problems need to be solved > anyhow. Just imagine at how Krita will want to present colour spaces in 3D (hint: CIE*Lab) and implement a 2D CIE*Lab graph for now. >> A way to paint the gamut would be to use the AtoB1 tag, transform a coarse >> sampling of all RGB or CMYK space and then use some sort of convex hull >> algorithm, or alpha shapes, to build the solid on Lab. This may also work >> for the tonge, it is just a matter of converting to xyY and take the xy >> coordinates. Making a color transform from the profile to XYZ identity does >> most of the work. Then there is a function to convert XYZ -> xyY. >> >> > Okay, so you are suggesting I try to take a set of colors, generated spaced > out over the different channels(so if I were to make 10 samples per > channel, RGB would give me 10³ colors and CMYK would give me 10⁴ colors... > perhaps a bit too many samples). Then transform those colors to XYZ(using > relative colorimetric mapping as indicated by your suggestion of the AtoB1 > tag), then to xyY, find the outliers, draw a polygon around them, and then > use that to give feedback on the gamut? In Oyranos is a more simple approch implemented [1]. This tool generates a saturation line going around from the primary colours over the secondary ones (R->RG->G->GB->B->BR->R ; same for Cmyk) and convert that through the according RGB or Cmyk profile to CIE*Lab. The CIE*Lab colours can then directly drawn as coordinates to the 2D graph. All math is integer based to get the desired clipping. -- kind regards Kai-Uwe www.oyranos.org [1] search for oyranos-profile-graph; It is used in KolorManager and ICC Examin ------------------------------------------------------------------------------ _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
