code: function updateBackground () {
          if ($G('coloredRadio').checked) {
              var color = domUtils.getStyle($G("colorPicker"), "background-color"),
                  bgimg = $G("url").value,
                  align = $G("repeatType").value,
                  backgroundObj = {
                      "background-repeat": "no-repeat",
                      "background-position": "center center"
                  };
  
              if (color) backgroundObj["background-color"] = color;
              if (bgimg) backgroundObj["background-image"] = 'url(' + bgimg + ')';
              if (align == 'self') {
                  backgroundObj["background-position"] = $G("x").value + "px " + $G("y").value + "px";
              } else if (align == 'repeat-x' || align == 'repeat-y' || align == 'repeat') {
                  backgroundObj["background-repeat"] = align;
              }
  
              editor.execCommand('background', backgroundObj);
          } else {
              editor.execCommand('background', null);
          }
      }
docs: /* 更新背景颜色