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precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D tex;
uniform float noise;
uniform float brightness;
uniform float contrast;
uniform float saturation;
mat4 brightnessMatrix() {
float b = brightness - 1.0;
return mat4(1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
b, b, b, 1);
}
mat4 contrastMatrix() {
float t = (1.0 - contrast) / 2.0;
return mat4(contrast, 0, 0, 0,
0, contrast, 0, 0,
0, 0, contrast, 0,
t, t, t, 1);
}
mat4 saturationMatrix() {
vec3 luminance = vec3(0.3086, 0.6094, 0.0820);
float oneMinusSat = 1.0 - saturation;
vec3 red = vec3(luminance.x * oneMinusSat);
red+= vec3(saturation, 0, 0);
vec3 green = vec3(luminance.y * oneMinusSat);
green += vec3(0, saturation, 0);
vec3 blue = vec3(luminance.z * oneMinusSat);
blue += vec3(0, 0, saturation);
return mat4(red, 0,
green, 0,
blue, 0,
0, 0, 0, 1);
}
// Fast generative noise function
float hash(vec2 p) {
return fract(sin(dot(p, vec2(12.9898, 78.233))) * 43758.5453);
}
void main() {
vec4 color = texture2D(tex, v_texcoord);
color *= brightnessMatrix() * contrastMatrix() * saturationMatrix();
float noiseHash = hash(v_texcoord);
float noiseAmount = (mod(noiseHash, 1.0) - 0.5);
color.rgb += noiseAmount * noise;
gl_FragColor = color;
}
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