I finally made a new release of OpenGTL, with a nearly full support of the CTL (Color Transformation Language) syntax. While large part of the standard library is still unavailable, it has all the features currently needed for Krita’s color spaces.
This allows to bring color management to color spaces that didn’t have that, and most specifically our RGB HDR (High-Dynamic Range) color spaces. It is especially interesting, because we need to have both a linear color space (for most high dynamic range operations, and if you want to do gamma correct scaling) and a non linear (a sRGB color space, which is used for color conversion, mostly with the painterly framework). So we were in need to be able to have profiles on top of those color spaces, and that is exactly what CTL is giving to us.
Back to gamma correct scaling, some times ago someone mentioned to me this link, scaling with non-linear color space gives a wrong result. Before we started using CTL based RGB color space, our HDR color space were an hybrid of sRGB (non-linear) and scRGB (linear) (don’t try to understand how we got there, I don’t either), and curiously, the scaling was wrong half of the time (don’t try to understand it was possible, I don’t either), but now, using the linear RGB color space, we can have gamma correct scaling: