[libcamera-devel] Colour Matrix control proposal

[David Plowman]

Hi everyone

One thing we've overlooked is the ability to return the colour matrix
used by the pipeline. This is particularly important for people
wanting to process raw files themselves, as we can then arrange for it
to be written into DNG files. (You might allow the matrix to be
written as well as returned; I think both are fine.)

I'd therefore like to propose a new control called ColourMatrix:

* It would hold an array of 9 floats representing a 3x3 matrix, listed
in normal "reading order".

* It is the cameraRGB -> sRGB matrix used by the ISP (you can find
them in Raspberry Pi camera tuning files under "rpi.ccm"). To be extra
clear, this is the matrix normally applied *after* white balancing,
and *before* the gamma transform.

I'm hoping this is relatively uncontroversial (??) so I'm happy to
create a patch. If people have other ideas, I'm of course delighted to
discuss and re-think.

Best regards
David