uniform sampler2D samp9; out vec4 ocol0; in vec2 uv0; void main() { vec4 c0 = texture(samp9, uv0); // Info: http://www.oreillynet.com/cs/user/view/cs_msg/8691 float avg = (0.222 * c0.r) + (0.707 * c0.g) + (0.071 * c0.b); ocol0 = vec4(avg, avg, avg, c0.a); }