@juit/qrcode

Juit GmbH's Own QR Code Generator

First of all, kudos are due to Alexey Ten who wrote the original qr-image package. Without his incredible work this project would not exist.

This package simply generate QR codes, using modern web standards like CompressionStreams, Promises (with async/await) and has zero dependencies on NodeJS or other frameworks (therefore making it suitable for inclusion in runtimes like Cloudflare Workers).

• Main API
  • Arguments
  • Options
• Bundler-friendly API
• Low-level API
  • The QRCode object
  • SVG paths (and PDFKit integration)
• Copyright Notice
• License

Main API

To generate a QR code simply use the generate(...) async function:

import { generate } from `@juit/qrcode`

const image = await generate('https://www.juit.com/', 'png')
// `image` here is a Uint8Array containing the PDF data

Arguments

• message: a string or Uint8Array containing the data to be included in the generated QR code
• format: the format of the QR code to generate, that is:
  • png: a PNG image (as a Uint8Array)
  • pdf: a PDF document (as a Uint8Array - uses compression)
  • svg: a SVG image (as a string)
  • pngData: the data URL (as a string) of a PNG image
  • pdfData: the data URL (as a string) of a PDF document
  • svgData: the data URL (as a string) of a SVG image
• options: an optional object containing encoding options

Options

• ecLevel: the error correction level for the QR code (default: M)
  • L: approximately 7% of error correction capability
  • M: approximately 15% of error correction capability
  • Q: approximately 25% of error correction capability
  • H: approximately 30% of error correction capability
• url: whether to optimize URLs in QR codes or not (default: false)
• scale: the number of pixels used for each dot in the matrix (default: 1 for PNG/SVG and 9 for PDF)
• margin: the size of the margin around the QR code in matrix modules (default: 4 as per the QR code specification - the quiet area)

Bundler-friendly API

If final bundle sizes are important for you, we also offer individual APIs for each format we generate. The bundler's own tree shaking algorithm should be able to then remove all irrelevant code.

The main functions are:

• generatePngQrCode(message, options?):
  asynchronously generates a QR code in PNG format (as a Promise<Uint8Array>)
• generatePdfQrCode(message, options?):
  asynchronously generates a QR code in PDF format (as a Promise<Uint8Array>)
• generateSvgQrCode(message, options?):
  synchronously generates a QR code in SVG format (as a string)

To generate data URLs on the other hand:

• generatePngDataQrCode(message, options?):
  asynchronously generates a QR code as a data URL in PNG format (as a Promise<string>)
• generatePdfDataQrCode(message, options?):
  asynchronously generates a QR code as a data URL in PDF format (as a Promise<string>)
• generateSvgDataQrCode(message, options?):
  synchronously generates a QR code as a data URL in PDF format (as a string)

The message and options consumed by these functions are the same ones described in the main api.

Low-level API

The low-level API splits the generation of a QR code from its rendering as an image.

• generateQrCode(message, options?):
  generates a QRCode object from the given message
• generatePng(qrcode, options?):
  asynchronously renders a previously generated QRCode as a PNG image (as a Promise<Uint8Array>)
• generatePdf(qrcode, options?):
  asynchronously renders a previously generated QRCode as a PDF document (as a Promise<Uint8Array>)
• generateSvg(qrcode, options?):
  synchronously renders a previously generated QRCode as a SVG image (as a string)

You can combine those APIs to (for example) generate a single QR code for a message, and then render it in multiple formats.

The message and options consumed by these functions are the same ones described in the main api.

The QRCode object

The object returned by generateQrCode(...) contains the following properties:

• version: the version of the QR code (1...40)
• ecLevel: the error correction level for the QR code (L, M, Q or H)
• size: The size (in pixels, or QR code blokcs) of the QR code
• matrix: The QR code matrix (where true is black, false is white)

SVG paths

The generateSvgPath(qrcode) function generate a SVG path for a QR code.

The returned SVG path will be a simple conversion of the QR code's own matrix into a square path of N "pixels" (where N is the size of the QR code's size of the matrix).

This can be scaled and positioned into a final SVG using the scale(...) and translate(...) basic SVG transformations.

This is also particulary useful with PDFKit's own implementation of SVG paths.

We can use it together with translate(...) and scale(...) to draw our QR code anywhere on the page, in any size. For example, to prepare a simple A4 document with a 10cm QR code smack in the middle we can:

// generate the QR code _structure_ for our message
const code = generateQrCode('https://www.juit.com/')

// generate the SVG path for our QR code
const path = generateSvgPath(code)

// calculate how to translate and scale our QR code in the page
const dpcm = 72 / 2.54             // PDFKit uses 72dpi (inches) we want metric!
const size = 10 * dpcm             // 10 cm (size of our QR code) in dots
const scale = size / code.size     // scale factor for our QR code to be 10 cm
const x = ((21 - 10) / 2) * dpcm   // center horizontally
const y = ((29.7 - 10) / 2) * dpcm // center vertically

// create a new A4 document, and stream it to "test.pdf"
const document = new PDFDocument({ size: 'A4' })
const stream = createWriteStream('test.pdf')
document.pipe(stream)

// draw our 10cm QR code right in the middle of the page
document
  .translate(x, y) // move to x = 5.5cm, y = 9.85cm
  .scale(scale)    // scale our QR code to 10cm width and height
  .path(path)      // draw our QR code smack in the middle of the page
  .fill('black')   // fill our QR code in black
  .end()           // finish up and close the document

// wait for the stream to finish
stream.on('finish', () => {
  // your PDF file is ready!
})