YIQ Color Filter

Very simple shader that changes hue, saturation and brightness (value) by using YIQ color space. Shader implementation based on this article

Demo image borrowed from GrafxKid

Shader code

shader_type canvas_item;

uniform float hue: hint_range(0.0, 360.0, 1.0) = 0.0;
uniform float saturation: hint_range(0.0, 10.0, 0.1) = 1.0;
uniform float value: hint_range(0.0, 10.0, 0.1) = 1.0;

void fragment() {
	vec4 color = texture(TEXTURE, UV);
	float vsu = value * saturation * cos(hue * PI / 180.0);
	float vsw = value * saturation * sin(hue * PI / 180.0);
	vec3 ret;
    ret.r = (.299 * value + .701 * vsu + .168 * vsw) * color.r
        +   (.587 * value - .587 * vsu + .330 * vsw) * color.g
        +   (.114 * value - .114 * vsu - .497 * vsw) * color.b;
    ret.g = (.299 * value - .299 * vsu - .328 * vsw) * color.r
        +   (.587 * value + .413 * vsu + .035 * vsw) * color.g
        +   (.114 * value - .114 * vsu + .292 * vsw) * color.b;
    ret.b = (.299 * value - .300 * vsu + 1.25 * vsw) * color.r
        +   (.587 * value - .588 * vsu - 1.05 * vsw) * color.g
        +   (.114 * value + .886 * vsu - .203 * vsw) * color.b;
	COLOR = vec4(ret, color.a);
}

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