html2canvas + JsPDF.js 导出pdf分页时的问题

问题描述

前一段时间实现了html2canvas + jspdf.js 导出pdf的功能项目当时没有测试做完就先搁置最近项目要上线发现分页时问题这篇文章记录一下之前的bug

import html2canvas from 'html2canvas';
import JsPDF from 'jspdf'
export function savePdf(el,  title) {
    html2canvas(el, {
      useCORS: true,
      allowTaint: true,
      dpi: 192,//导出pdf清晰度
      scale:2,
    })
    .then(async (canvas) => {
       // 新建JsPDF对象
       const pdf = new JsPDF("p", "mm", "a4");
       let ctx = canvas.getContext('2d'),
            a4w = 192, a4h = 277,    //A4大小，210mm x 297mm，四边各保留10mm的边距，显示区域190x277
            imgHeight = Math.floor(a4h * canvas.width / a4w),    //按A4显示比例换算一页图像的像素高度
            renderedHeight = 0;
            while(renderedHeight < canvas.height) {
                let page = document.createElement("canvas");
                page.width = canvas.width;
                page.height = Math.min(imgHeight, canvas.height - renderedHeight);//可能内容不足一页

                //用getImageData剪裁指定区域，并画到前面创建的canvas对象中
                page.getContext('2d').putImageData(ctx.getImageData(0, renderedHeight, canvas.width, Math.min(imgHeight, canvas.height - renderedHeight)), 0, 0);
                pdf.addImage(page.toDataURL('image/jpeg', 1.0), 'JPEG', 10, 10, a4w, Math.min(a4h, a4w * page.height / page.width));    //添加图像到页面，保留10mm边距

                renderedHeight += imgHeight;
                if(renderedHeight < canvas.height)
                    pdf.addPage();//如果后面还有内容，添加一个空页

                page = null
            }
            pdf.save(title + ".pdf");
    }).catch((e) => {
      console.log(e)
    }).finally(() => {});
}