Port the lmmse gamma step to the other demosaicers

[ggbutcher (Glenn Butcher)]

@hanatos

i think this is most prominently due to the old ahd implementation dt had copied from ufraw. that one did some fake lab conversion on the pixels and computed gradients only on luminance, not on colour. it does show severe mazing artifacts if no white balance is applied before. i think many others do not have this property.

Thanks, makes sense to bear-of-little-brain here. I may do some experimentation with the librtprocess algorithms, see if this holds out in current implementations.

@hanatos

i very much dislike this camera-raw multiplier. once you do that, your colour coordinates are off/irrecoverably out of gamut. the dng matrices come with illuminant anyways, and you can replace them by a more accurate lut/spectral input transform.

From the start, it always seem to me to be a rather egregious thing to do to the data. Some years ago, I tried making a colorchecker matrix profile with an unwhitebalanced target shot, and the results were quite satisfying in terms of preserving color “richness”, for lack of a more precise term. Here’s the post I did on it:

GIMP 2.10.6 out-of-range RGB values from .CR2 file

Okay, I know this thread is getting entirely too long, but I’ve been picking through this year’s images and re-processing selected ones with the new camera profile I made back in post #102, then comparing them with what I did with the old profile that required separate white balance. The difference is marked; I’m starting with richer colors. Here’s an example, first the old rendering: [DSG_1099] Then, the new rendering with the uwb profile: [DSG_1099_uwb] Now, the first profile might jus…