Adds support for the extend option for linear and radial shadings.

src/pattern.js

@@ -46,6 +46,11 @@ var Pattern = (function PatternClosure() {
 
 var Shadings = {};
 
+// A small number to offset the first/last color stops so we can insert ones to
+// support extend.  Number.MIN_VALUE appears to be too small and breaks the
+// extend.
+Shadings.SMALL_NUMBER = 1e-7;
+
 // Radial and axial shading have very similar implementations
 // If needed, the implementations can be broken into two classes
 Shadings.RadialAxial = (function RadialAxialClosure() {
@@ -54,7 +59,6 @@ Shadings.RadialAxial = (function RadialAxialClosure() {
     this.coordsArr = dict.get('Coords');
     this.shadingType = dict.get('ShadingType');
     this.type = 'Pattern';
-
     this.ctx = ctx;
     var cs = dict.get('ColorSpace', 'CS');
     cs = ColorSpace.parse(cs, xref, res);
@@ -72,7 +76,6 @@ Shadings.RadialAxial = (function RadialAxialClosure() {
       var extendArr = dict.get('Extend');
       extendStart = extendArr[0];
       extendEnd = extendArr[1];
-      TODO('Support extend');
     }
 
     this.extendStart = extendStart;
@@ -88,16 +91,38 @@ Shadings.RadialAxial = (function RadialAxialClosure() {
     // 10 samples seems good enough for now, but probably won't work
     // if there are sharp color changes. Ideally, we would implement
     // the spec faithfully and add lossless optimizations.
-    var step = (t1 - t0) / 10;
     var diff = t1 - t0;
+    var step = diff / 10;
+
+    var colorStops = this.colorStops = [];
+
+    // Protect against bad domains so we don't end up in an infinte loop below.
+    if (t0 >= t1 || step <= 0) {
+      // Acrobat doesn't seem to handle these cases so we'll ignore for
+      // now.
+      info('Bad shading domain.');
+      return;
+    }
 
-    var colorStops = [];
     for (var i = t0; i <= t1; i += step) {
       var rgbColor = cs.getRgb(fn([i]));
       var cssColor = Util.makeCssRgb(rgbColor[0], rgbColor[1], rgbColor[2]);
       colorStops.push([(i - t0) / diff, cssColor]);
     }
 
+    // XXX: Extend start and end does work in Chrome. Tested in v21.
+    if (!extendStart) {
+      // Insert a color stop at the front and offset the first real color stop
+      // so it doesn't conflict with the one we insert.
+      colorStops.unshift([0, 'rgba(255,255,255,0)']);
+      colorStops[1][0] += Shadings.SMALL_NUMBER;
+    }
+    if (!extendEnd) {
+      // Same idea as above in extendStart but for the end.
+      colorStops[colorStops.length - 1][0] -= Shadings.SMALL_NUMBER;
+      colorStops.push([1, 'rgba(255,255,255,0)']);
+    }
+
     this.colorStops = colorStops;
   }
 

test/pdfs/.gitignore

@@ -34,3 +34,4 @@
 !gradientfill.pdf
 !basicapi.pdf
 !mixedfonts.pdf
+!shading_extend.pdf