html2canvas把div保存高清图的方法代码

http://www.bootcdn.cn/（可以搜索html2canvans）

1.选择html2canvas版本（这个版本可以放大倍数保证图片清晰）

默认生成的 canvas 图片在 retina 设备上显示很模糊，处理成 2 倍图能解决这个问题：

var w = $("#code").width();
var h = $("#code").height();

//要将 canvas 的宽高设置成容器宽高的 2 倍
var canvas = document.createElement("canvas");
canvas.width = w * 2;
canvas.height = h * 2;
canvas.style.width = w + "px";
canvas.style.height = h + "px";
var cOntext= canvas.getContext("2d");
//然后将画布缩放，将图像放大两倍画到画布上
context.scale(2,2);

html2canvas(document.querySelector("#code"), {
    canvas: canvas,
    onrendered: function(canvas) {
        ...
    }
});

下载方法：

.on(&＃39;click&＃39;,&＃39;.download&＃39;,function(){
                $(&＃39;#mycanvas&＃39;).remove();
                var _height=$(&＃39;.skinReport&＃39;).height();
                //滚到顶部
                $(&＃39;html, body&＃39;).animate({scrollTop:0});

                if(confirm(&＃39;是否下载肌肤检测报告？&＃39;))
                {

                    setTimeout(function(){
                        var canvas = document.createElement("canvas"),
                            w=$(&＃39;#skinReport&＃39;).width(),
                            h=$(&＃39;#skinReport&＃39;).height();
                        canvas.width = w * 2;
                        canvas.height = h * 2;
                        canvas.style.width = w + "px";
                        canvas.style.height = h + "px";
                        var cOntext= canvas.getContext("2d");
//然后将画布缩放，将图像放大两倍画到画布上
                        context.scale(2,2);
                        html2canvas(document.getElementById(&＃39;skinReport&＃39;), {
                            allowTaint: false,
                            taintTest: true,
                            canvas: canvas,
                            onrendered: function(canvas) {
                                canvas.id = "mycanvas";
                                canvas.style.display = &＃39;none&＃39;;
                                document.body.appendChild(canvas);
                                //生成base64图片数据

                                imgData = canvas.toDataURL(type);
                                //var newImg = document.createElement("img");
                                //newImg.src =  dataUrl;
                                //document.body.appendChild(newImg);
                                //console.log(imgData);

                                var _fixType = function(type) {
                                    type = type.toLowerCase().replace(/jpg/i, &＃39;jpeg&＃39;);
                                    var r = type.match(/png|jpeg|bmp|gif/)[0];
                                    return &＃39;image/&＃39; + r;
                                };
                                // 加工image data，替换mime type
                                imgData = imgData.replace(_fixType(type),&＃39;image/octet-stream&＃39;);
                                /**
                                 * 在本地进行文件保存
                                 * @param  {String} data     要保存到本地的图片数据
                                 * @param  {String} filename 文件名
                                 */
                                var saveFile = function(data, filename){
                                    var save_link = document.createElementNS(&＃39;http://www.w3.org/1999/xhtml&＃39;, &＃39;a&＃39;);
                                    save_link.href = data;
                                    save_link.download = filename;

                                    var event = document.createEvent(&＃39;MouseEvents&＃39;);
                                    event.initMouseEvent(&＃39;click&＃39;, true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
                                    save_link.dispatchEvent(event);
                                };

                                // 下载后的问题名
                                var filename = aname+&＃39;肌肤检测报告&＃39; + (new Date()).getTime() + &＃39;.&＃39; + type;
                                // download
                                saveFile(imgData,filename);
                            },
                            width:1512,
                            height:15000
                        })
                    },2500)
                }
                else
                {
                    return;
                }

            })