/* Shader for conversion of RGB textures into Grayscale textures.
 * Uses standard formula for conversion:
 * (w)2006 by Mario Kleiner. Licensed under MIT license.
*/

#extension GL_ARB_texture_rectangle : enable

const int maxSamples = 255;
uniform sampler2DRect Image;

void main()
{
    int i;
    vec4 sum = vec4(0.0);
    vec2 texcoord = vec2(gl_FragCoord.x * float(maxSamples), gl_FragCoord.y);
    
    for (i=0; i<maxSamples; i++) {
	sum+=texture2DRect(Image, texcoord)*0.001;
	texcoord.s += 1.0;
    }

    gl_FragColor = sum;
}