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precision highp float;
varying vec2 v_texcoord;
uniform sampler2D tex;
uniform float brightness;
uniform float contrast;
uniform float saturation;
uniform float noise;
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) * (1.0 - saturation);
vec3 red = vec3(luminance.x);
red.x += saturation;
vec3 green = vec3(luminance.y);
green.y += saturation;
vec3 blue = vec3(luminance.z);
blue.z += saturation;
return mat4(red, 0,
green, 0,
blue, 0,
0, 0, 0, 1);
}
float noiseAmount(vec2 p) {
vec3 p3 = fract(vec3(p.xyx) * 1689.1984);
p3 += dot(p3, p3.yzx + 33.33);
float hash = fract((p3.x + p3.y) * p3.z);
return (mod(hash, 1.0) - 0.5) * noise;
};
void main() {
vec4 color = texture2D(tex, v_texcoord);
// Do *not* transpose the combined matrix when multiplying
color = brightnessMatrix() * contrastMatrix() * saturationMatrix() * color;
color.xyz += noiseAmount(v_texcoord);
gl_FragColor = color;
}
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