Mathjax in Wechat

topng.js

var i=0;
      var svgs;
       function drawCanvas(){

         if(i==0){
           svgs=document.getElementsByClassName("MathJax_SVG");
         }else{
           if(i>=svgs.length){
             return;
           }
         }



        var img = new Image();
      var DOMURL = self.URL || self.webkitURL || self;
      var canvas = document.getElementById("canvas");
        var ctx = canvas.getContext("2d");
         canvas.height= svgs[i].getElementsByTagName("svg")[0].clientHeight+200
         canvas.width= svgs[i].getElementsByTagName("svg")[0].clientWidth+200
         svgs[i].style.height=svgs[i].getElementsByTagName("svg")[0].clientHeight*1.25+"px";
         svgs[i].style.width=svgs[i].getElementsByTagName("svg")[0].clientWidth*1.25+10+"px";
          svgs[i].style.overflow="hidden";

          var svgString = new XMLSerializer().serializeToString( svgs[i].getElementsByTagName("svg")[0]);
          img.src = 'data:image/svg+xml;base64,' + btoa(unescape(encodeURIComponent(svgString)) );
           img.iddd=i
         document.body.appendChild(img);
         img.onload = function () {
              ctx.drawImage(img, 0, 0);
           var im = canvas.toDataURL("image/png");
           var imgg=new Image();
           imgg.style.cssText = 'max-width:none !important;';
           imgg.src=im;
            svgs[i].innerHTML=""
            svgs[i].appendChild(imgg);
           i++;
           drawCanvas();
            };            

         }
 drawCanvas();