Implemented basic version of smask

pdf.js

@@ -1926,11 +1926,32 @@ var CanvasGraphics = (function() {
             var pixels = imgData.data;
 
             var alpha = 25;
-            if (image.dict.has("SMask"))
+            if (image.dict.has("SMask")) {
+                var smask = image.dict.get("SMask");
+                smask = this.xref.fetchIfRef(smask);
                 // Specifies either a shape or opacity mask to be
                 // applied to the image samples
                 TODO("SMask");
+            }
 
+            if (smask) {
+                var smaskDict = smask.dict;
+                if (!smaskDict)
+                    error("No dictionary for smask");
+                var smaskBitsPerComponent = smaskDict.get("BitsPerComponent") || smaskDict.get("BPC");
+                if (!smaskBitsPerComponent)
+                    error("Bad BPC for smask");
+                var max = (1 << bitsPerComponent) - 1;
+
+                var matte = smaskDict.get("Matte");
+                if (matte) {
+                    TODO(matte);
+                }
+
+                for (var i = 0; i < 4 * w * h; ++i) {
+                    pixels[i] = image.getChar() * smask.getChar() / max;
+                }
+            } else {
                 for (var i = 0; i < 4 * w * h; ++i) {
                     // TODO blend if SMask is a mask image
                     if (3 === i % 4) {
@@ -1939,6 +1960,7 @@ var CanvasGraphics = (function() {
                         pixels[i] = image.getChar();
                     }
                 }
+            }
             tmpCtx.putImageData(imgData, 0, 0);
 
             this.ctx.drawImage(tmpCanvas, 0, 0);