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--- isp:hue_rotation [2019/05/09 00:27] – Igor Yefmov
+++ isp:hue_rotation [2023/09/05 04:53] – Igor Yefmov
@@ Line 1: / Line 1: @@
 ====== Hue rotation ======
+"Hue rotation" is a global (every pixel) shift of the image's color spectrum by a given radial offset (considering the [[https://simple.wikipedia.org/wiki/Color_wheel|color wheel]]).
+To rotate the color vector by an angle \(\Theta\) the following matrix multiplication is done:
+\[
+\begin{bmatrix}
+R \\
+G \\
+B
+\end{bmatrix}
+\times
+\begin{bmatrix}
+cox(\Theta) & sin(\Theta) & 0 \\
+-sin(\Theta) & cos(\Theta) & 0 \\
+& 0 & 1
+\end{bmatrix}
+\]
+===== In RGB color space =====
+===== In HSL color space =====
 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:
 <code c++>// pseudo-code

SUB2r