ECG/src/utils/htmlPdf.js

import html2Canvas from 'html2canvas';
import jsPDF from 'jspdf';

const htmlToPdf = {
  getPdfBase64(title, id) {
    return new Promise((resolve) => {
      html2Canvas(document.querySelector(id), {
        allowTaint: false,
        taintTest: false,
        logging: false,
        useCORS: true,
        dpi: window.devicePixelRatio * 4, // 将分辨率提高到特定的DPI 提高四倍
        scale: 4, // 按比例增加分辨率
      }).then((canvas) => {
        const pdf = new jsPDF('p', 'mm', 'a4'); // A4纸，纵向
        const ctx = canvas.getContext('2d'),
          a4w = 190,
          a4h = 272; // A4大小，210mm x 297mm，四边各保留10mm的边距，显示区域190x277
        let 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) {
          const page = document.createElement('canvas');
          page.width = canvas.width;
          const pageHeight = Math.min(imgHeight, canvas.height - renderedHeight); // 可能内容不足一页
          page.height = pageHeight;

          // 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,
                pageHeight,
              ),
              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 += pageHeight;
          if (renderedHeight < canvas.height) {
            pdf.addPage(); // 如果后面还有内容，添加一个空页
          }
        }
        const pdfBase64String = pdf.output('datauristring'); // 获取 base64 编码的 PDF 文件
        resolve(pdfBase64String); // 解析 base64 字符串
      });
    });
  },

  getPdf(title, id) {
    html2Canvas(document.querySelector(id), {
      allowTaint: false,
      taintTest: false,
      logging: false,
      useCORS: true,
      dpi: window.devicePixelRatio * 4, // 将分辨率提高到特定的DPI 提高四倍
      scale: 4, // 按比例增加分辨率
    }).then((canvas) => {
      const pdf = new jsPDF('p', 'mm', 'a4'); // A4纸，纵向
      const ctx = canvas.getContext('2d'),
        a4w = 190,
        a4h = 272; // A4大小，210mm x 297mm，四边各保留10mm的边距，显示区域190x277
      let 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) {
        const page = document.createElement('canvas');
        page.width = canvas.width;
        const pageHeight = Math.min(imgHeight, canvas.height - renderedHeight); // 可能内容不足一页
        page.height = pageHeight;

        // 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,
              pageHeight,
            ),
            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 += pageHeight;
        if (renderedHeight < canvas.height) {
          pdf.addPage(); // 如果后面还有内容，添加一个空页
        }
      }
      pdf.save(title + '.pdf'); // 保存 PDF 文件
    });
  },
};

export default htmlToPdf;