=== modified file 'src/com/goldencode/p2j/ui/client/gui/driver/web/res/p2j.screen.js'
--- src/com/goldencode/p2j/ui/client/gui/driver/web/res/p2j.screen.js	2015-08-21 16:58:11 +0000
+++ src/com/goldencode/p2j/ui/client/gui/driver/web/res/p2j.screen.js	2015-08-21 20:06:59 +0000
@@ -1497,18 +1497,36 @@
     */
    Window.prototype.drawImage = function(ctx, x, y, width, height, imgData, imgDataOffset)
    {
-      var img = ctx.createImageData(width, height);
+      /**
+       * Pixels must be returned as non-premultiplied alpha values according to:
+       * http://www.w3.org/TR/2dcontext/#pixel-manipulation
+       */
+      var img = ctx.getImageData(this.origin.x + x, this.origin.y + y, width, height);
       var data = img.data;
       var pixelsInBytes = width * height * 4;
-
-      for (var i = 0, j = imgDataOffset; i < pixelsInBytes; i += 4, j += 4)
+      var j = imgDataOffset;
+      for (var i = 0; i < pixelsInBytes; i += 4, j += 4)
       {
-         data[i]     = imgData[j];
-         data[i + 1] = imgData[j + 1];
-         data[i + 2] = imgData[j + 2];
-         data[i + 3] = imgData[j + 3];
-     }
-     ctx.putImageData(img, this.origin.x + x, this.origin.y + y);
+         var alpha = imgData[j + 3];
+         var gamma = (256 - alpha) * data[i + 3];
+         var beta = gamma >> 8;
+         if (alpha == 255)
+         {
+            data[i]     = imgData[j];
+            data[i + 1] = imgData[j + 1];
+            data[i + 2] = imgData[j + 2];
+            data[i + 3] = imgData[j + 3];
+         }
+         else if (alpha > 0)
+         {
+            /** server sends premultiplied image data */
+            data[i]     = (imgData[j]     * alpha + data[i]     * beta) >> 8;
+            data[i + 1] = (imgData[j + 1] * alpha + data[i + 1] * beta) >> 8;
+            data[i + 2] = (imgData[j + 2] * alpha + data[i + 2] * beta) >> 8;
+            data[i + 3] = (imgData[j + 3] * alpha + gamma) >> 8;
+         }
+      }
+      ctx.putImageData(img, this.origin.x + x, this.origin.y + y);
    };
    
    /**