OpenSpace/shaders/framebuffer/computeAveLum.frag

/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
 *                                                                                       *
 * Copyright (c) 2014-2018                                                               *
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 * permit persons to whom the Software is furnished to do so, subject to the following   *
 * conditions:                                                                           *
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 * The above copyright notice and this permission notice shall be included in all copies *
 * or substantial portions of the Software.                                              *
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,   *
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A         *
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT    *
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 ****************************************************************************************/

#version __CONTEXT__

layout (location = 0) out vec4 finalColor;

uniform int bufferWidth;
uniform int bufferHeight;
uniform sampler2D hdrTexture;

in vec2 texCoord;

void main() {
    vec4 color = vec4(0.0);
    float fH = float(bufferHeight);
    float fW = float(bufferWidth);

    float sum = 0.f;
    for (int i = 0; i < bufferHeight; ++i) {
        for (int j = 0; j < bufferWidth; ++j) {
            vec2 texCoord = vec2(float(i) / fH, float(j) / fW);
            vec4 tmpColor = texture(hdrTexture, texCoord);    
            float lum = dot(tmpColor.xyz, vec3(0.2126f, 0.7152f, 0.0722f));
            sum += log(lum + 0.00001); // 0.00001 to avoid log(0) from black pixels
        }
    }

    finalColor = vec4(vec3(exp(sum / (fH * fW))), 1.0);
}