vue将html页面生成高清晰pdf文件的方法

 createImage(){//生成图片->pdf
        let _this = this;
        
        //----此处是解决页面带滚动条的时候截图不全问题
        window.pageYoffset = 0;
        document.documentElement.scrollTop = 0;
        document.body.scrollTop = 0;'
        //----------------------------------------
        
        let canvas = document.createElement("canvas");
        let context = canvas.getContext("2d");
        let _articleHtml = document.getElementById('imageTofile');
        let _w = _articleHtml.clientWidth;
        let _h = _articleHtml.clientHeight;
        
        //-----这里解决生成的pdf不清晰的问题 先放大3倍----后面再缩小3倍
        let scale = 3;
        canvas.width = _w * scale;
        canvas.height = _h * scale;
        context.scale(scale, scale);
        
        
        let opts = {
            scale: 1,
            width: _w,
            height: _h,
            canvas: canvas,
            useCORS: true
        };  
          (window.html2canvas || html2canvas)(_articleHtml, opts).then(canvas => {//IOS13.4无效解决 和{(intermediate value)(intermediate value)} is not a function+;
            _this.createPdfAll(canvas, scale);
           });
      },

        createPdfAll (canvas, scale) {//生成图片->pdf
        //-----------宽高缩小3倍---------------------
        let contentWidth = canvas.width / scale
        let contentHeight = canvas.height / scale
        //--------------------
        let pdf = new jsPDF('', 'pt', [contentWidth, contentHeight+50]) //此处加50是pdf最后离底部的空白距离。根据需要自行调节
        let pageData = canvas.toDataURL('image/jpeg', 1.0);
        //这里只生成了一页的pdf，并未截断，需要截断的话在此处操作
        pdf.addImage(pageData, 'JPEG', 0, 0, contentWidth, contentHeight)
        
        //这里是将pdf的流文件---》file文件
        let filename = 'question.pdf' ;
        let datauri = pdf.output('dataurlstring');
        let file = this.dataURLtoFile(datauri,filename);
        
        // 以文件的形式上传给服务器
        this.uploadImg(file)
      },

 dataURLtoFile(dataurl, filename) {
            var arr = dataurl.split(',');
            var mime = arr[0].match(/:(.*?);/)[1];
            var bstr = atob(arr[1]);
            var n = bstr.length; 
            var u8arr = new Uint8Array(n);
            while(n--){undefined
                u8arr[n] = bstr.charCodeAt(n);
            }
            //转换成file对象
            return new File([u8arr], filename, {type:mime});
            //转换成成blob对象
            //return new Blob([u8arr],{type:mime});
        },