code: function processNodeRuleWithREM(nodeRule, imageReplaces, rootFontSize){
      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))
  
      function __getURL(bgURL){
          return _.trim(bgURL.split('url').join(''), '()"\'')
      }
      function __generatorCSSObj(img){
          return {
              "background-image": "url("+img.sprite+")",
              "background-position":  "-"+img.x/rootFontSize+"rem -"+img.y/rootFontSize+"rem",
              "-webkit-background-size": img.spriteWidth / rootFontSize + "rem",
              "-moz-background-size": img.spriteWidth / rootFontSize + "rem",
              "-o-background-size": img.spriteWidth / rootFontSize + "rem",
              "background-size": img.spriteWidth / rootFontSize + "rem"
          }
      }
  }
docs: partical