code: function (bounds) {
          bounds = this.adjustBounds(bounds);
          // Make a list, so that getFullRequestString uses literal "," 
          var extent = [bounds.left, bounds. bottom, bounds.right, bounds.top];
  
          var imageSize = this.getImageSize(); 
          
          // make lists, so that literal ','s are used 
          var url = this.getFullRequestString(
                       {mapext:   extent,
                        imgext:   extent,
                        map_size: [imageSize.w, imageSize.h],
                        imgx:     imageSize.w / 2,
                        imgy:     imageSize.h / 2,
                        imgxy:    [imageSize.w, imageSize.h]
                        });
          
          return url;
      }
docs: Method: getURL
  Return a query string for this layer
  
  Parameters:
  bounds - {<OpenLayers.Bounds>} A bounds representing the bbox
  for the request
  
  Returns:
  {String} A string with the layer's url and parameters and also
  the passed-in bounds and appropriate tile size specified
  as parameters.