Differences

This shows you the differences between two versions of the page.

--- isp:brightness [2023/09/10 20:56] – [Algorithm] Igor Yefmov
+++ isp:brightness [2023/09/10 21:49] (current) – [Calculation reference] Igor Yefmov
@@ Line 20: / Line 20: @@
 To calculate luminosity we just find the max and min of the triplet and get a simple average:
 \[L = \frac{min(R, G, B)+max(R, G, B)}{2}\]
+Brightness adjustment is a trivial addition, clamping the value to its proper limits:
+\[
+L` = L + br \\
+L` \in [0..4095]
+\]
 The slope \(k_R\) for the red component calculation depends on whether \(L\) is above or below the middle:
@@ Line 26: / Line 33: @@
 \begin{cases}
 R / L & \text{if} \; L \leq 2047 \\
-\frac{R - 2047}{L - 2047} & \text{if} \; L > 2047
+\frac{R - 4095}{L - 4095} & \text{if} \; L > 2047
 \end{cases}
 \]
-Brightness adjustment is a trivial addition, clamping the value to its proper limits:
+Finding the "middle point" value also depends on whether the \(L\) is above or below the middle:
+\[
+R =
+\begin{cases}
+k_R * 2047 & \text{if} \; L \leq 2047 \\
+- k_R * 2047 & \text{if} \; L > 2047
+\end{cases}
+\]
+If we are crossing the middle luma boundary as the result of this adjustment - flip the slope:
 \[
-L` = L + br \\
+k_R = 2 - k_R
-L` \in [0..4095]
 \]

SUB2r