Algorithm for Hue/Saturation Adjustment Layer from Photoshop

Question

Does anyone know how adjustment layers work in Photoshop? I need to generate a result image having a source image and HSL values from Hue/Saturation adjustment layer. Conversion

Answer 1

When the “Colorize” checkbox is checked, the lightness of the underlying layer is combined with the values of the Hue and Saturation sliders and converted from HSL to RGB according to the equations at https://en.wikipedia.org/wiki/HSL_and_HSV#From_HSL . (The Lightness slider just remaps the lightness to a subset of the scale as you can see from watching the histogram; the effect is pretty awful and I don’t see why anyone would ever use it.)