code: function (url) {
              if (this.$.width) {
                  url += ",width=" + ImageService.normalizeImageSize(this.$.width);
              }
  
              if (this.$.height) {
                  url += ",height=" + ImageService.normalizeImageSize(this.$.height);
              }
  
              return url;
          }
docs: *
  the spreadshirt image server provides images in normalized sizes between
  50px and 1200px within 50px steps.
  
  @param {String} url - the url of the image
  @return {String} the url extended with normalized sizes