rewrite CMYK to RGB conversion

src/colorspace.js

@@ -369,55 +369,16 @@ var DeviceCmykCS = (function DeviceCmykCSClosure() {
   DeviceCmykCS.prototype = {
     getRgb: function cmykcs_getRgb(color) {
       var c = color[0], m = color[1], y = color[2], k = color[3];
-      var c1 = 1 - c, m1 = 1 - m, y1 = 1 - y, k1 = 1 - k;
+
-
+      // CMYK -> CMY: http://www.easyrgb.com/index.php?X=MATH&H=14#text14
-      var x, r, g, b;
+      c = (c * (1-k) + k);
-      // this is a matrix multiplication, unrolled for performance
+      m = (m * (1-k) + k);
-      // code is taken from the poppler implementation
+      y = (y * (1-k) + k);
-      x = c1 * m1 * y1 * k1; // 0 0 0 0
+
-      r = g = b = x;
+      // CMY -> RGB: http://www.easyrgb.com/index.php?X=MATH&H=12#text12
-      x = c1 * m1 * y1 * k;  // 0 0 0 1
+      r = (1-c);
-      r += 0.1373 * x;
+      g = (1-m);
-      g += 0.1216 * x;
+      b = (1-y);
-      b += 0.1255 * x;
-      x = c1 * m1 * y * k1;  // 0 0 1 0
-      r += x;
-      g += 0.9490 * x;
-      x = c1 * m1 * y * k;   // 0 0 1 1
-      r += 0.1098 * x;
-      g += 0.1020 * x;
-      x = c1 * m * y1 * k1;  // 0 1 0 0
-      r += 0.9255 * x;
-      b += 0.5490 * x;
-      x = c1 * m * y1 * k;   // 0 1 0 1
-      r += 0.1412 * x;
-      x = c1 * m * y * k1;   // 0 1 1 0
-      r += 0.9294 * x;
-      g += 0.1098 * x;
-      b += 0.1412 * x;
-      x = c1 * m * y * k;    // 0 1 1 1
-      r += 0.1333 * x;
-      x = c * m1 * y1 * k1;  // 1 0 0 0
-      g += 0.6784 * x;
-      b += 0.9373 * x;
-      x = c * m1 * y1 * k;   // 1 0 0 1
-      g += 0.0588 * x;
-      b += 0.1412 * x;
-      x = c * m1 * y * k1;   // 1 0 1 0
-      g += 0.6510 * x;
-      b += 0.3137 * x;
-      x = c * m1 * y * k;    // 1 0 1 1
-      g += 0.0745 * x;
-      x = c * m * y1 * k1;   // 1 1 0 0
-      r += 0.1804 * x;
-      g += 0.1922 * x;
-      b += 0.5725 * x;
-      x = c * m * y1 * k;    // 1 1 0 1
-      b += 0.0078 * x;
-      x = c * m * y * k1;    // 1 1 1 0
-      r += 0.2118 * x;
-      g += 0.2119 * x;
-      b += 0.2235 * x;
 
       return [r, g, b];
     },