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/**
* Hue and saturation adjustment
* https://github.com/evanw/glfx.js
* hue: -1 to 1 (-1 is 180 degrees in the negative direction, 0 is no change, etc.
* saturation: -1 to 1 (-1 is solid gray, 0 is no change, and 1 is maximum contrast)
*/
const HueSaturationShader = {
name: 'HueSaturationShader',
uniforms: {
'tDiffuse': { value: null },
'hue': { value: 0 },
'saturation': { value: 0 }
},
vertexShader: /* glsl */`
varying vec2 vUv;
void main() {
vUv = uv;
gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
}`,
fragmentShader: /* glsl */`
uniform sampler2D tDiffuse;
uniform float hue;
uniform float saturation;
varying vec2 vUv;
void main() {
gl_FragColor = texture2D( tDiffuse, vUv );
// hue
float angle = hue * 3.14159265;
float s = sin(angle), c = cos(angle);
vec3 weights = (vec3(2.0 * c, -sqrt(3.0) * s - c, sqrt(3.0) * s - c) + 1.0) / 3.0;
float len = length(gl_FragColor.rgb);
gl_FragColor.rgb = vec3(
dot(gl_FragColor.rgb, weights.xyz),
dot(gl_FragColor.rgb, weights.zxy),
dot(gl_FragColor.rgb, weights.yzx)
);
// saturation
float average = (gl_FragColor.r + gl_FragColor.g + gl_FragColor.b) / 3.0;
if (saturation > 0.0) {
gl_FragColor.rgb += (average - gl_FragColor.rgb) * (1.0 - 1.0 / (1.001 - saturation));
} else {
gl_FragColor.rgb += (average - gl_FragColor.rgb) * (-saturation);
}
}`
};
export { HueSaturationShader };