From 881d0b9954ac952715641516a6fd444fa432355b Mon Sep 17 00:00:00 2001
From: Vincent Lejeune <vljn@ovi.com>
Date: Fri, 28 Mar 2014 23:30:26 +0100
Subject: [PATCH] Factorize luminance computation.

---
 data/shaders/bloom.frag           |  4 ++--
 data/shaders/utils/getCIEXYZ.frag | 17 +++++++++++++++++
 src/graphics/shaders.cpp          |  1 +
 3 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 data/shaders/utils/getCIEXYZ.frag

diff --git a/data/shaders/bloom.frag b/data/shaders/bloom.frag
index 3be3cb60f..2bccf2dfc 100644
--- a/data/shaders/bloom.frag
+++ b/data/shaders/bloom.frag
@@ -9,12 +9,12 @@ varying vec2 uv;
 #define FragColor gl_FragColor
 #endif
 
+vec3 getCIEYxy(vec3 rgbColor);
 
 void main()
 {
-	vec3 weights = vec3(0.2126, 0.7152, 0.0722); // ITU-R BT. 709
 	vec3 col = texture(tex, uv).xyz;
-	float luma = dot(weights, col);
+	float luma = getCIEYxy(col).x;
 
 	col *= smoothstep(1., 2., luma);
 
diff --git a/data/shaders/utils/getCIEXYZ.frag b/data/shaders/utils/getCIEXYZ.frag
new file mode 100644
index 000000000..f4f5d2bb5
--- /dev/null
+++ b/data/shaders/utils/getCIEXYZ.frag
@@ -0,0 +1,17 @@
+// Using numerical value from here
+// http://content.gpwiki.org/index.php/D3DBook:High-Dynamic_Range_Rendering
+
+vec3 getCIEYxy(vec3 rgbColor)
+{
+    // convert rgb to srgb
+    vec3 sRGBColor = vec3(pow(rgbColor.x, 1. / 2.2), pow(rgbColor.y, 1. / 2.2), pow(rgbColor.z, 1. / 2.2));
+
+    mat3 sRGB2XYZ = mat3(
+        vec3(.4125, .2126, .0193),
+        vec3(.3576, .7152, .1192),
+        vec3(.1805, .0722, .9505));
+
+    vec3 XYZ = sRGB2XYZ * sRGBColor;
+    float sum = dot(vec3(1.), XYZ);
+    return vec3(XYZ.y, XYZ.xy / sum);
+}
\ No newline at end of file
diff --git a/src/graphics/shaders.cpp b/src/graphics/shaders.cpp
index eac01581d..60d867ff1 100644
--- a/src/graphics/shaders.cpp
+++ b/src/graphics/shaders.cpp
@@ -1768,6 +1768,7 @@ namespace FullScreenShader
 	{
 		Program = LoadProgram(
             GL_VERTEX_SHADER, file_manager->getAsset("shaders/screenquad.vert").c_str(),
+            GL_FRAGMENT_SHADER, file_manager->getAsset("shaders/utils/getCIEXYZ.frag").c_str(),
             GL_FRAGMENT_SHADER, file_manager->getAsset("shaders/bloom.frag").c_str());
 		uniform_texture = glGetUniformLocation(Program, "tex");
 		uniform_low = glGetUniformLocation(Program, "low");