// 导出页面为PDF格式
import html2Canvas from "html2canvas";
import JsPDF from "jspdf";
export default {
  install(Vue, options) {
    Vue.prototype.getPdf = function() {
      var title = this.htmlTitle;
      html2Canvas(document.querySelector("#pdfDom"), {
        allowTaint: true
      }).then(function(canvas) {
        var pdf = new JsPDF("p", "mm", "a4"); // A4纸，纵向

        var ctx = canvas.getContext("2d");

        var a4w = 210;
        var a4h = 297; // A4大小，210mm x 297mm，四边不保留边距，显示区域210x297 (四边各保留20mm的边距，显示区域170x257)(pass)

        var imgHeight = Math.floor((a4h * canvas.width) / a4w); // 按A4显示比例换算一页图像的像素高度

        var renderedHeight = 0;

        while (renderedHeight < canvas.height) {
          var 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，并画到前面建立的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",
            0,
            0,
            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();
          } // 若是后面还有内容，添加一个空页
          // delete page;
        }
        pdf.save(title + ".pdf");
      });
    };
  }
};