NodeJS + Express + PDFKit + node-qrcode: Not able to add QR code to PDF

Question

I am trying to implement a QR code in a PDF document using PDFkit (https://github.com/foliojs/pdfkit) and node-qrcode (https://github.com/soldair/node-qrcode).

Implementing PDF document:

  const doc = new PDFDocument({
    margin: 0,
    size: 'LETTER'
  })

  doc.pipe(fs.createWriteStream('/files/result.pdf'))
  doc.pipe(res)

Creating QR code and adding it to the PDF:

  var opts = {
    errorCorrectionLevel: 'H',
    type: 'image/png',
    quality: 0.9,
    margin: 1,
    color: {
      dark:"#000000",
      light:"#FFFFFF"
    }
  }
  QRCode.toDataURL('http://link.to.website', function (err, url) {
    if (err) throw err
    doc.image(url, 50, 45, { width: 50 })
    console.log(url)
  })

Close the PDF:

doc.end()

Console output of the url from QRCode is correctly formatted and no error messages from PDFKit:

data:image/png;base64,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

The problem is that no image is displayed in the produced PDF. If I use any other functions (than doc.image), e.g. doc.text(), doc.circle() all elements works fine and added to the PDF.

Any idea how to solve this?

Answer 1

toDataURL() is a asynchronous method. I didn't wait for it to complete. Closed the PDF document after it completed, and that worked.