A simple implementation of modifying the HSL (Hue, Saturation, Lightness) components of an image.
The aim is to imitate the Hue/Saturation
adjustment layer sliders in Adobe Photoshop. This is mostly accomplished for hue and lightness. However, for saturation values larger than 0 the intensity and curve for (probably) the red channel still differs from Photoshop.
Hue:
Saturation:
Lightness: