| void main() { |
| // Generate a random number based on the fragment position. For this |
| // random number generator, we use the "GLSL rand" function |
| // that seems to be floating around on the internet. It works under |
| // the assumption that sin(<big number>) oscillates with high frequency |
| // and sampling it will generate "randomness". Since we're using this |
| // for rendering and not cryptography it should be OK. |
| |
| // For each channel c, add the random offset to the pixel to either bump |
| // it up or let it remain constant during quantization. |
| float r = fract(sin(dot(sk_FragCoord.xy, vec2(12.9898, 78.233))) * 43758.5453); |
| sk_OutColor = clamp(1.0 / 255.0 * vec4(r) + sk_InColor, 0, 1); |
| } |
| |
| @test(testData) { |
| return GrDitherEffect::Make(); |
| } |