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--- isp:contrast [2023/09/06 10:37] – [Integer arithmetic] Igor Yefmov
+++ isp:contrast [2023/09/10 21:51] – [In RGB color space] Igor Yefmov
@@ Line 7: / Line 7: @@
 ===== In RGB color space =====
-As with the [[isp::brightness]] adjusting contrast in RGB color space requires us to pay attention to proportionally adjust the individual color components of the pixel to preserve their relative ratios.
-Traditionally the luminance is calculated as (see [[isp:luminance]])
+Each component's contrast adjustment is based on its value and the adjustment itself is calculated as
 \[
-lum = 0.2126 * R + 0.7152 * G + 0.0722 * B
+component = (component' - 0.5) * k^2 + 0.5 \\
-\]
-With that in mind each component's contrast adjustment is based on its luma's weight \(k\) and the adjustment itself is calculated as
-\[
-component = (component' - 0.5) * (contrast * k)^2 + 0.5 \\
 component' \in [0..1.0] \\
 contrast \in ]0..2.0]%%
 \]
-which looks like this:
-\[
-\begin{bmatrix}
-R - 0.5 \\
-G - 0.5 \\
-B - 0.5
-\end{bmatrix}
- \times
-\begin{bmatrix}
-.2126^2 & 0 & 0 \\
-& 0.7152^2 & 0 \\
-& 0 & 0.0722^2
-\end{bmatrix} \times contrast^2
-+
-\begin{bmatrix}
-.5 \\
-.5 \\
-.5
-\end{bmatrix}
-\]
 ==== Integer arithmetic ====

SUB2r