if (!c || !c.width || !c.height) throw new Error('canvas');
        cv = c;
        /* html2pdf would JPEG-encode the huge canvas again and store it in the PDF; hand it a tiny stand-in instead */
        try {
          var t = document.createElement('canvas');
          t.width = 40; t.height = Math.max(1, Math.round(40 * c.height / c.width));
          if (this && this.prop && 'canvas' in this.prop) this.prop.canvas = t;
        } catch (e) {}
      }).toPdf().get('pdf').then(function(pdf){
        var n = pdf.internal.getNumberOfPages();
        while (n > 1) { pdf.deletePage(n); n--; }
        pdf.setPage(1);
        pdf.addImage(fitJpeg(cv), 'JPEG', 0, 0, 210, 297);
      }).save();
  }
  bPdf.addEventListener('click', function(){
    run(bPdf, function(){
      return exportPdf(5).catch(function(){ return exportPdf(4); }).catch(function(){ return exportPdf(3); }).catch(function(){ return exportPdf(2); });
    });
  });
  bImg.addEventListener('click', function(){
    run(bImg, function(){
      return html2pdf().set(opt).from(page).toCanvas().get('canvas').then(function(c){
        return new Promise(function(res){
          c.toBlob(function(blob){
            var a = document.createElement('a');
            a.href = URL.createObjectURL(blob); a.download = 'Digestion-Notes-A4.png';
            document.body.appendChild(a); a.click(); a.remove();
            setTimeout(function(){ URL.revokeObjectURL(a.href); res(); }, 3000);
          }, 'image/png');
        });
      });
    });
  });
})();
</script>
</body>
</html>