@amydin/filterous/lib/util.js

Instagram-like photo manipulation library for Node.js and Javascript on browser

// Based on: https://gist.github.com/mjackson/5311256
module.exports.RGBtoHSV = (r, g, b) => {
  r /= 255, g /= 255, b /= 255;

 let max = Math.max(r, g, b), min = Math.min(r, g, b);
 let h, s, v = max;

 let d = max - min;
 s = max == 0 ? 0 : d / max;

 if (max == min) {
   h = 0; // achromatic
 } else {
   switch (max) {
     case r: h = (g - b) / d + (g < b ? 6 : 0); break;
     case g: h = (b - r) / d + 2; break;
     case b: h = (r - g) / d + 4; break;
   }

   h /= 6;
 }

 return [ h, s, v ];
}

module.exports.HSVtoRGB = (h, s, v) => {
  let r, g, b;

  let i = Math.floor(h * 6);
  let f = h * 6 - i;
  let p = v * (1 - s);
  let q = v * (1 - f * s);
  let t = v * (1 - (1 - f) * s);

  switch (i % 6) {
    case 0: r = v, g = t, b = p; break;
    case 1: r = q, g = v, b = p; break;
    case 2: r = p, g = v, b = t; break;
    case 3: r = p, g = q, b = v; break;
    case 4: r = t, g = p, b = v; break;
    case 5: r = v, g = p, b = q; break;
  }

  return [ r * 255, g * 255, b * 255 ];
}