docs: function processNodeRule (nodeRule, imageReplaces, coll2x, coll3x) {
      var img, imgKey, __url
      _.each(nodeRule.declarations, function(e){
          if(e.property == 'background-image'){
              __url = __getURL(e.value)
              img = img || imageReplaces[__url]
              imgKey = img? __url: imgKey
          }
      })
      if(!img) return
      // 修改节点
      updateNodeByMerge(nodeRule, __generatorCSSObj(img))
      // 更新2x 3x 收集器
      updateCollectMX(imgKey, imageReplaces, nodeRule.selectors, coll2x, coll3x)
  
      function __getURL(bgURL){
          return _.trim(bgURL.split('url').join(''), '()"\'')
      }
      function __generatorCSSObj(img){
          return {
              "background-image": "url("+img.sprite+")",
              "background-position":  "-"+img.x+"px -"+img.y+"px"
          }
      }
  }