用html2canvas.js 将前端HTML页面生成图片

首先去html2canvas官网下载html2canvas.js文件
html2canvas官网地址：http://html2canvas.hertzen.com/
HTML

<div id="host_file" class="container">
     <div id="view" class="print_wrap">
            <div class="host_file_top_title_box">
                <p>123</p>
                <p>456</p>
            </div>   
            <div id="moveDiv"  onclick="renderPdf">下载页面</div>
      </div>
</div>   

js

function renderPdf() {
            var dom=document.getElementsByClassName("container")[0];
            var domWrap =document.getElementsByClassName("print_wrap")[0];
            var width = dom.offsetWidth; //获取dom 宽度
            var height = dom.offsetHeight; //获取dom 高度
            var offsetTop = dom.offsetTop; 
            var scaleBy =1;
            var canvas =document.createElement('canvas');
            canvas.width = width * scaleBy; //定义canvas 宽度 * 缩放
            canvas.height = (height + offsetTop) * scaleBy; //定义canvas（高度 +偏移量 ）*缩放
            canvas.style.width =width * scaleBy + 'px';
            canvas.style.height =(height + offsetTop) * scaleBy + 'px';
            var context =canvas.getContext('2d');
            context.scale(scaleBy, scaleBy);
            var filename =(new Date()).getTime() + '.' + "png";
            html2canvas(dom, {
                background:"#ffffff",
                canvas: canvas,
                useCORS: true,
                scale: 1, 
                width: width, 
                height: height
            }).then(function(canvas){
                       var type ='png';
                       var imgData =canvas.toDataURL(type);
                       var _fixType =function(type) {
                              type =type.toLowerCase().replace(/jpg/i, 'jpeg');
                              var r =type.match(/png|jpeg|bmp|gif/)[0];
                           　 return 'images/' + r;
                       };
                       imgData =imgData.replace(_fixType(type),'image/octet-stream');
                       var saveFile =function(data, filename){
                                var save_link =document.createElementNS('http://www.w3.org/1999/xhtml', 'a');
                                save_link.href =data;
                                save_link.download =filename;
                                var event =document.createEvent('MouseEvents');
                                event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
                                save_link.dispatchEvent(event);
                       };
                       saveFile(imgData,filename);
                  })
      　　　}