The adjust algorithm already uses a symbolic constant for gamma. Let's introduce similar constants for contrast and saturation to prevent copying the numeric defaults to multiple places. Reviewed-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com> Reviewed-by: Robert Mader <robert.mader@collabora.com> Signed-off-by: Milan Zamazal <mzamazal@redhat.com> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>