shadowBlendConvert.js

gistfile1.txt

// http://stackoverflow.com/questions/5560248/programmatically-lighten-or-darken-a-hex-color-or-rgb-and-blend-colors
// credits to https://github.com/PimpTrizkit/
function shadeBlendConvert(percent, from, to) {
  if (
    typeof percent != 'number' ||
    percent < -1 ||
    percent > 1 ||
    typeof from != 'string' ||
    (from[0] != 'r' && from[0] != '#') ||
    (to && typeof to != 'string')
  )
    return null; //ErrorCheck

  function pSBCr(d){
    var l = d.length,
      RGB = {};
    if (l > 9) {
      d = d.split(',');
      if (d.length < 3 || d.length > 4) return null; //ErrorCheck
      (RGB[0] = i(d[0].split('(')[1])),
        (RGB[1] = i(d[1])),
        (RGB[2] = i(d[2])),
        (RGB[3] = d[3] ? parseFloat(d[3]) : -1);
    } else {
      if (l == 8 || l == 6 || l < 4) return null; //ErrorCheck
      if (l < 6)
        d =
          '#' +
          d[1] +
          d[1] +
          d[2] +
          d[2] +
          d[3] +
          d[3] +
          (l > 4 ? d[4] + '' + d[4] : ''); //3 or 4 digit
      (d = i(d.slice(1), 16)),
        (RGB[0] = (d >> 16) & 255),
        (RGB[1] = (d >> 8) & 255),
        (RGB[2] = d & 255),
        (RGB[3] = -1);
      if (l == 9 || l == 5)
        (RGB[3] = r(RGB[2] / 255 * 10000) / 10000),
          (RGB[2] = RGB[1]),
          (RGB[1] = RGB[0]),
          (RGB[0] = (d >> 24) & 255);
    }
    return RGB;
  };

  var i = parseInt,
    r = Math.round,
    h = from.length > 9,
    h =
      typeof to == 'string'
        ? to.length > 9 ? true : to == 'c' ? !h : false
        : h,
    b = percent < 0,
    percent = b ? percent * -1 : percent,
    to = to && to != 'c' ? to : b ? '#000' : '#FFF',
    f = pSBCr(from),
    t = pSBCr(to);
  if (!f || !t) return null; //ErrorCheck
  if (h)
    return (
      'rgb' +
      (f[3] > -1 || t[3] > -1 ? 'a(' : '(') +
      r((t[0] - f[0]) * percent + f[0]) +
      ',' +
      r((t[1] - f[1]) * percent + f[1]) +
      ',' +
      r((t[2] - f[2]) * percent + f[2]) +
      (f[3] < 0 && t[3] < 0
        ? ')'
        : ',' +
          (f[3] > -1 && t[3] > -1
            ? r(((t[3] - f[3]) * percent + f[3]) * 10000) / 10000
            : t[3] < 0 ? f[3] : t[3]) +
          ')')
    );
  else
    return (
      '#' +
      (
        0x100000000 +
        r((t[0] - f[0]) * percent + f[0]) * 0x1000000 +
        r((t[1] - f[1]) * percent + f[1]) * 0x10000 +
        r((t[2] - f[2]) * percent + f[2]) * 0x100 +
        (f[3] > -1 && t[3] > -1
          ? r(((t[3] - f[3]) * percent + f[3]) * 255)
          : t[3] > -1 ? r(t[3] * 255) : f[3] > -1 ? r(f[3] * 255) : 255)
      )
        .toString(16)
        .slice(1, f[3] > -1 || t[3] > -1 ? undefined : -2)
    );
}