add integration tests for PNG export & scaled export

src/js/controller/settings/exportimage/PngExportController.js

@@ -145,7 +145,11 @@
   ns.PngExportController.prototype.onDownloadClick_ = function (evt) {
     // Create PNG export.
     var canvas = this.createPngSpritesheet_();
+    this.downloadCanvas_(canvas);
+  };
 
+  // Used and overridden in casper integration tests.
+  ns.PngExportController.prototype.downloadCanvas_ = function (canvas) {
     // Generate file name
     var name = this.piskelController.getPiskel().getDescriptor().name;
     var fileName = name + '.png';

src/js/utils/FrameUtils.js

@@ -269,6 +269,19 @@
       }
 
       return chunkFrames;
+    },
+
+    toFrameGrid : function (normalGrid) {
+      var frameGrid = [];
+      var w = normalGrid[0].length;
+      var h = normalGrid.length;
+      for (var x = 0 ; x < w ; x++) {
+        frameGrid[x] = [];
+        for (var y = 0 ; y < h ; y++) {
+          frameGrid[x][y] = normalGrid[y][x];
+        }
+      }
+      return frameGrid;
     }
   };
 })();