code: function(options) {
          options = options || {};
  
          var params = [
              'position=' + (options.position || 'top-left'),
              'x=' + toInt(options.x || 0),
              'y=' + toInt(options.y || 0)
          ];
  
          if (options.imageIdentifier) {
              params.push('img=' + options.imageIdentifier);
          }
  
          if (options.width > 0) {
              params.push('width=' + toInt(options.width));
          }
  
          if (options.height > 0) {
              params.push('height=' + toInt(options.height));
          }
  
          return this.append('watermark:' + params.join(','));
      }
docs: Applies a watermark on top of the original image
  
  @param  {Object} [options]
  @param  {Number} [options.img] Image identifier of the image to apply as watermark
  @param  {Number} [options.width]  Width of the watermark, in pixels
  @param  {Number} [options.height] Height of the watermark, in pixels
  @param  {String} [options.position=top-left] Position of the watermark. Values:
  "top-left", "top-right", "bottom-left", "bottom-right" and "center"
  @param  {Number} [options.x] Number of pixels in the X-axis the watermark image
  should be offset from the original position
  @param  {Number} [options.y] Number of pixels in the Y-axis the watermark image
  should be offset from the original position
  @return {Imbo.ImageUrl}