html2canvas saves high-definition pictures in divs (graphic tutorial)-HTML Tutorial-php.cn

html2canvas saves high-definition pictures in divs (graphic tutorial)

亚连

Release： 2018-05-18 16:00:06

Original

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1. Select the html2canvas version (this version can be enlarged to ensure clear images)

The default generated canvas image is very blurry on retina devices. Processing it into a 2x image can solve this problem:

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) {
        ...
    }
});

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Download method:

.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;
                }
            })

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The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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