Factorize luminance computation.

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);
 

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);
+}

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");