HSV でシフトするより無理のない感じがある
YIQ は距離が彩度、色相が角度の極座標空間
なので、rgb から yiq の現在地確かめて、hueShift 分回転させてあげることで実現
code:.glsl
// Source - https://stackoverflow.com/q/9234724
// Posted by Andrea3000, modified by community. See post 'Timeline' for change history
// Retrieved 2026-02-08, License - CC BY-SA 3.0
uniform sampler2DRect texture;
const mat3 rgb2yiq = mat3(0.299, 0.587, 0.114,
0.595716, -0.274453, -0.321263,
0.211456, -0.522591, 0.311135);
const mat3 yiq2rgb = mat3(1.0, 0.9563, 0.6210, 1.0, -0.2721, -0.6474, 1.0, -1.1070, 1.7046);
uniform float hue;
void main() {
vec3 yColor = rgb2yiq * texture2DRect(texture, gl_TexCoord0.st).rgb;
float originalHue = atan(yColor.b, yColor.g);
float finalHue = originalHue + hue;
float chroma = sqrt(yColor.b*yColor.b+yColor.g*yColor.g);
vec3 yFinalColor = vec3(yColor.r, chroma * cos(finalHue), chroma * sin(finalHue));
gl_FragColor = vec4(yiq2rgb*yFinalColor, 1.0);
}