/* 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 vec3 ColorToGrayWeights = vec3(0.3, 0.59, 0.11); uniform sampler2DRect Image; void main() { vec4 incolor = texture2DRect(Image, gl_TexCoord[0].st); float luminance = dot(incolor.rgb, ColorToGrayWeights); gl_FragColor.a = incolor.a; gl_FragColor.rgb = vec3(luminance); }