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

//要將 canvas 的寬高設置成容器寬高的 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");
//然后將畫布縮放，將圖像放大兩倍畫到畫布上
context.scale(2,2);

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

.on('click','.download',function(){
                $('#mycanvas').remove();
                var _height=$('.skinReport').height();
                //滾到頂部
                $('html, body').animate({scrollTop:0});

                if(confirm('是否下載肌膚檢測報告？'))
                {

                    setTimeout(function(){
                        var canvas = document.createElement("canvas"),
                            w=$('#skinReport').width(),
                            h=$('#skinReport').height();
                        canvas.width = w * 2;
                        canvas.height = h * 2;
                        canvas.style.width = w + "px";
                        canvas.style.height = h + "px";
                        var context = canvas.getContext("2d");
//然后將畫布縮放，將圖像放大兩倍畫到畫布上
                        context.scale(2,2);
                        html2canvas(document.getElementById('skinReport'), {
                            allowTaint: false,
                            taintTest: true,
                            canvas: canvas,
                            onrendered: function(canvas) {
                                canvas.id = "mycanvas";
                                canvas.style.display = 'none';
                                document.body.appendChild(canvas);
                                //生成base64圖片數據

                                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, 'jpeg');
                                    var r = type.match(/png|jpeg|bmp|gif/)[0];
                                    return 'image/' + r;
                                };
                                // 加工image data，替換mime type
                                imgData = imgData.replace(_fixType(type),'image/octet-stream');
                                /**
                                 * 在本地進行文件保存
                                 * @param  {String} data     要保存到本地的圖片數據
                                 * @param  {String} filename 文件名
                                 */
                                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);
                                };

                                // 下載后的問題名
                                var filename = aname+'肌膚檢測報告' + (new Date()).getTime() + '.' + type;
                                // download
                                saveFile(imgData,filename);
                            },
                            width:1512,
                            height:15000
                        })
                    },2500)
                }
                else
                {
                    return;
                }

            })