Request for RGBY tone curves


#1

This kind of curves look overall like the standard rgb curves but they could help with very saturated colors or with strong primaries.
They work in a similar way of the rawtherapee’s luminance curves, the difference is that we process the rgb input too with curves , find the (rgb+curves) luminance and “merge” with the (input luminance + curve)

Example from a Playraw, look at the car’s rear lights

original

rgb curves

rgby curves

Pseudo-code

RGB=RGB

Y_input = R * 0.2126729 + G * 0.7151521 + B * 0.0721750

Y_output=Y_input + curve

RGB2=RGB + curve    

Y2=R2 * 0.2126729 + G2 * 0.7151521 + B2 * 0.0721750 (luminance of RGB2)

RGB_output= (RGB2  /  Y2) * Y_output

It could be possible to test these curves in rawtherapee ? :slight_smile: