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Hue rotation
Really, no magic here, once you process the image in HSL color space. The operation is as trivial as adding or subtracting a specified value from the pixel's \(H\) component:
// pseudo-code void hue_rotation(/*array of pixels*/image, double _hue){ for(const & pixel: image){ pixel.hue = std::clamp(pixel.hue + _hue, 0., 360.); // hue is in range [0..360]° } }