On Mon, 4 Mar 2019 22:07:24 +1100 Graeme Gill <grae...@argyllcms.com> wrote:
> Pekka Paalanen wrote: > > Hi, > > > Does that even make any difference if the output space was linear at > > blending step, and gamma was applied after that? > > as mentioned earlier, I think talk of using device links is now a red herring. > > If it is desirable to do blending in a linear light space (as is typically > the case), then this can be implemented in a way that leverages color > management, > without interfering with it. In a color managed workflow all color values > intended > for a particular output will be converted to that devices output space either > by the client or the compositor on the clients behalf. The installed output > device > profile then can provide the necessary blending information. Even if > a device colorspace is not terribly additive for the purposes of > accurate profile creation, RGB devices are generally additive enough to > approximate linear light mixing with per channel lookup curves. It's > pretty straightforward to use the ICC profile to create such curves > (for each of the RGB channels in turn with the others at zero, lookup > the Relative Colorimetric XYZ value and take the dot product with the > 100% channel value. Ensure the curves are monotonic, and normalize them > to map 0 and 1 unchanged.) > Compositing in a linear light space has to occur to sufficiently high > precision of course, so as not to introduce quantization errors. > After composition the inverse curves would be applied to return to the > output device space. Excellent! Thank you, pq
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