code: function() {
          if (OpenLayers.CANVAS_SUPPORTED && this.imgDiv && !this.isLoading) {
              if (!this.canvasContext) {
                  var canvas = document.createElement("canvas");
                  canvas.width = this.size.w;
                  canvas.height = this.size.h;
                  this.canvasContext = canvas.getContext("2d");
                  this.canvasContext.drawImage(this.imgDiv, 0, 0);
              }
              return this.canvasContext;
          }
      }
docs: APIMethod: getCanvasContext
  Returns a canvas context associated with the tile image (with
  the image drawn on it).
  Returns undefined if the browser does not support canvas, if
  the tile has no image or if it's currently loading.
  
  The function returns a canvas context instance but the
  underlying canvas is still available in the 'canvas' property:
  (code)
  var context = tile.getCanvasContext();
  if (context) {
  var data = context.canvas.toDataURL('image/jpeg');
  }
  (end)
  
  Returns:
  {Boolean}