SOURCE

$("#creat").click(function(){
    html2canvas($("body"),{ // $(".myImg")是你要复制生成canvas的区域，可以自己选
        onrendered:function(canvas){
              dataURL =canvas.toDataURL("image/png");
             $("body").append(canvas);
              console.log(dataURL);

              //下载图片
              $('#down_button').attr( 'href' ,  dataURL ) ;
              $('#down_button').attr( 'download' , 'myjobdeer.png' ) ;
          },
          width:320,
          height:400
      })
 })

<a type="button" id="down_button"><button id="creat">点击复制图片</button></a>
<div class="myImg" style="position:relative;">
    <img src="body_background.jpg">
</div>