将html元素保存为图片

初始需求是echarts绘制的图表保存为图片，

后来发现，echarts图标之外，还有一个参数input/button也要放到图片中

于是，技术实现从简单的《echarts导出为图片》

变成了较为复杂的《html元素导出为图片》

 

先放出已经实现的《echarts导出为图片》的代码，

    // 导出 图片
    generatePic() {let parseTime = dayUtils.parseTime(new Date(), '');var myChart = document.getElementById('fitModel_echart_Option_Div_all')// var myChart = echarts.init(document.getElementById(this.showFitModel_pingjia_factor));var img = new Image();// pieMyChart1 要导出的图表img.src = myChart.getDataURL({type: "png",pixelRatio: 1, //放大2倍backgroundColor: "#000",});let projectName = this.projectInfo.projectName || ''projectName = '敏感性分析：' + projectNameimg.onload = function () {var canvas = document.createElement("canvas");canvas.width = img.width;canvas.height = img.height;var ctx = canvas.getContext("2d");ctx.drawImage(img, 0, 0);var dataURL = canvas.toDataURL("image/png");var a = document.createElement("a");var event = new MouseEvent("click");a.download = projectName + "分析结果_图片" + parseTime + ".png" || "下载图片名称";// 将生成的URL设置为a.href属性a.href = dataURL;// 触发a的单击事件
        a.dispatchEvent(event);a.remove();};},

 

 

照抄的《html元素导出为图片》相关js代码

//获取canvas配置项
    getCanvasOption(shareContent){let canvasEle = document.querySelector('canvas');if(canvasEle){document.getElementById('dialog').removeChild(canvasEle)}let width = shareContent.offsetWidth; //获取dom 宽度let height = shareContent.offsetHeight; //获取dom 高度let canvas = document.createElement("canvas"); //创建一个canvas节点let scale = 2; //定义任意放大倍数 支持小数
canvas.getContext("2d").scale(scale, scale); //获取context,设置scale canvas.width = width * scale; //定义canvas 宽度 * 缩放canvas.height = height * scale; //定义canvas高度 *缩放
canvas.style.cssText = 'width: '+ width +'px; height: '+ height +'px';let opts = {scale: scale, // 添加的scale 参数canvas: canvas, //自定义 canvas// logging: true, //日志开关，便于查看html2canvas的内部执行流程width: width, //dom 原始宽度
          height: height,useCORS: true // 【重要】开启跨域配置
      };return opts;},downloadFile(content, fileName) { //下载base64图片let base64ToBlob = function(code) {let parts = code.split(';base64,');let contentType = parts[0].split(':')[1];let raw = window.atob(parts[1]);let rawLength = raw.length;let uInt8Array = new Uint8Array(rawLength);for(let i = 0; i < rawLength; ++i) {uInt8Array[i] = raw.charCodeAt(i);}return new Blob([uInt8Array], {type: contentType});};let aLink = document.createElement('a');let blob = base64ToBlob(content); //new Blob([content]);let evt = document.createEvent("HTMLEvents");evt.initEvent("click", true, true); //initEvent 不加后两个参数在FF下会报错  事件类型，是否冒泡，是否阻止浏览器的默认行为aLink.download = fileName;aLink.href = URL.createObjectURL(blob);aLink.click();},//下载图片
    downLoadPic() {     let shareContent = document.getElementById('cert');//需要截图的包裹的（原生的）DOM 对象let opts = this.getCanvasOption(shareContent);this.html2canvas(shareContent,opts).then((canvas) =>{// document.getElementById('dialog').appendChild(canvas);let context = canvas.getContext('2d');// 【重要】关闭抗锯齿context.mozImageSmoothingEnabled = false;context.webkitImageSmoothingEnabled = false;context.msImageSmoothingEnabled = false;context.imageSmoothingEnabled = false;let MIME_TYPE = "image/png";let imgURL = canvas.toDataURL(MIME_TYPE);this.downloadFile(imgURL,'文件名')});},//下载pdf
    downLoadPdf() {let shareContent = document.getElementById('cert');//需要截图的包裹的（原生的）DOM 对象let opts = this.getCanvasOption(shareContent);this.html2canvas(shareContent,opts).then((canvas) =>{let contentWidth = canvas.widthlet contentHeight = canvas.heightlet pageHeight = contentWidth / 592.28 * 841.89let leftHeight = contentHeightlet position = 0let imgWidth = 595.28let imgHeight = 592.28 / contentWidth * contentHeightlet pageData = canvas.toDataURL('image/jpeg', 1.0)let PDF = new this.JsPDF('', 'pt', 'a4')if (leftHeight < pageHeight) {PDF.addImage(pageData, 'JPEG', 0, 0, imgWidth, imgHeight)} else {while (leftHeight > 0) {PDF.addImage(pageData, 'JPEG', 0, position, imgWidth, imgHeight)leftHeight -= pageHeightposition -= 841.89if (leftHeight > 0) {PDF.addPage()}}}PDF.save('文件名' + '.pdf')});},