colorFormats.js

/**
 * Some helper functions to transform/handle values
 * between known colour formats 
 * atm: RGB, hex, HSL
 */

// RGB > Hex
function rgbToHex(r, g, b) {
  function componentToHex(c) {
    var hex = c.toString(16);
    return hex.length == 1 ? "0" + hex : hex;
  }

  return "#" + componentToHex(r) + componentToHex(g) + componentToHex(b);
}
// Hex > RGB
function hexToRgb(hex) {
    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result ? {
        r: parseInt(result[1], 16),
        g: parseInt(result[2], 16),
        b: parseInt(result[3], 16)
    } : null;
}

// If there's a risk that some calculations
// might return rgb values < 0 or > 255, then
// this function will keep them in bounds
function fixRGB(rgb) {
  for (var j = 0; j < rgb.length; j++) {
    if (rgb[j] < 0) {
      rgb[j] = 0;
    } else if (rgb[j] > 255) {
      rgb[j] = 255;
    }
  }
  
  return rgb;
}


// RGB <=> HSL
function rgbToHsl(r, g, b) {
	r /= 255, g /= 255, b /= 255;
	var max = Math.max(r, g, b), min = Math.min(r, g, b);
	var h, s, l = (max + min) / 2;

	if (max == min) { h = s = 0; } 
	else {
		var d = max - min;
		s = l > 0.5 ? d / (2 - max - min) : d / (max + min);

		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*100+0.5)|0, ((s*100+0.5)|0) + '%', ((l*100+0.5)|0) + '%'];
}
function hslToRgb(h, s, l) {
  var r, g, b;

  if(s == 0){
      r = g = b = l; // achromatic
  }else{
      var hue2rgb = function hue2rgb(p, q, t){
          if(t < 0) t += 1;
          if(t > 1) t -= 1;
          if(t < 1/6) return p + (q - p) * 6 * t;
          if(t < 1/2) return q;
          if(t < 2/3) return p + (q - p) * (2/3 - t) * 6;
          return p;
      }

      var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
      var p = 2 * l - q;
      r = hue2rgb(p, q, h + 1/3);
      g = hue2rgb(p, q, h);
      b = hue2rgb(p, q, h - 1/3);
  }

  return [Math.round(r * 255), Math.round(g * 255), Math.round(b * 255)];
}