From 5cc8fdd83d90dca3f7c7cb5c7fdef4c3ea018aed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Du=C5=A1an=20Poizl?= <nou.spiro@gmail.com>
Date: Tue, 20 Dec 2022 22:27:15 +0100
Subject: [PATCH] Simple grey world white balance

---
 imagescrollareagl.cpp | 15 +++++++++++++++
 imagescrollareagl.h   |  1 +
 shaders/image.frag    |  3 +++
 3 files changed, 19 insertions(+)

diff --git a/imagescrollareagl.cpp b/imagescrollareagl.cpp
index af77ed4..baaeb76 100644
--- a/imagescrollareagl.cpp
+++ b/imagescrollareagl.cpp
@@ -353,6 +353,8 @@ void ImageWidget::paintGL()
         m_program->setUniformValue("zoom", 1.0f/m_scale);
         m_program->setUniformValue("bw", m_bwImg && !m_superpixel);
         m_program->setUniformValue("invert", m_invert);
+        if(m_superpixel)m_program->setUniformValue("whiteBalance", m_whiteBalance[0], m_whiteBalance[1], m_whiteBalance[2]);
+        else m_program->setUniformValue("whiteBalance", 1.0f, 1.0f, 1.0f);
 #ifdef COLOR_MANAGMENT
         m_program->setUniformValue("srgb", m_srgb);
 #endif
@@ -642,6 +644,19 @@ void ImageWidget::debayer()
     f->glGenerateMipmap(GL_TEXTURE_2D);
     f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
     f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
+
+    int size = std::max(m_imgWidth, m_imgHeight);
+    int level = 0;
+    while(size >>= 1)level++;
+    int w,h;
+    f3->glGetTexLevelParameteriv(GL_TEXTURE_2D, level, GL_TEXTURE_WIDTH, &w);
+    f3->glGetTexLevelParameteriv(GL_TEXTURE_2D, level, GL_TEXTURE_HEIGHT, &h);
+    uint16_t pixel[w*h*4];
+    f3->glGetTexImage(GL_TEXTURE_2D, level, GL_RGBA, GL_UNSIGNED_SHORT, pixel);
+    float maxRGB = std::max(std::max(pixel[0], pixel[1]), pixel[2]);
+    m_whiteBalance[0] = maxRGB / pixel[0];
+    m_whiteBalance[1] = maxRGB / pixel[1];
+    m_whiteBalance[2] = maxRGB / pixel[2];
 }
 
 ImageScrollAreaGL::ImageScrollAreaGL(Database *database, QWidget *parent) : QWidget(parent)
diff --git a/imagescrollareagl.h b/imagescrollareagl.h
index 3b3ab21..a052e48 100644
--- a/imagescrollareagl.h
+++ b/imagescrollareagl.h
@@ -52,6 +52,7 @@ class ImageWidget : public QOpenGLWidget
     float m_range;
     float m_dx, m_dy;
     float m_scale;
+    float m_whiteBalance[3];
     bool m_blockRepaint;
     bool m_bwImg;
     bool m_invert;
diff --git a/shaders/image.frag b/shaders/image.frag
index a86af41..0dc9d81 100644
--- a/shaders/image.frag
+++ b/shaders/image.frag
@@ -5,6 +5,7 @@ uniform vec3 mtf_param;
 uniform bool bw;
 uniform bool invert;
 uniform bool srgb;
+uniform vec3 whiteBalance;
 in vec2 qt_TexCoord0;
 out vec4 color;
 
@@ -40,6 +41,8 @@ void main(void)
 
     if(srgb)color.rgb = Linear2sRGB(color.rgb);
 
+    color.rgb *= whiteBalance;
+
     if(any(lessThan(qt_TexCoord0, vec2(0.0))) || any(greaterThan(qt_TexCoord0, vec2(1.0))))
         color = vec4(0.0, 0.0, 0.0, 1.0);