libcamera: software_isp: Add saturation control

Saturation control is added on top of the colour correction matrix.  A
method of saturation adjustment that can be fully integrated into the
colour correction matrix is used.  The control is available only if Ccm
algorithm is enabled.

The control uses 0.0-2.0 value range, with 1.0 being unmodified
saturation, 0.0 full desaturation and 2.0 quite saturated.

The saturation is adjusted by converting to Y'CbCr colour space,
applying the saturation value on the colour axes, and converting back to
RGB.  ITU-R BT.601 conversion is used to convert between the colour
spaces, for no particular reason.

The colour correction matrix is applied before gamma and the given
matrix is suitable for such a case.  Alternatively, the transformation
used in libcamera rpi ccm.cpp could be used.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

0 files changed, 0 insertions, 0 deletions