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QRCode #86

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mcya opened this issue Mar 12, 2020 · 0 comments
Open

QRCode #86

mcya opened this issue Mar 12, 2020 · 0 comments

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@mcya
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mcya commented Mar 12, 2020

node-qrcode

QR code/2d barcode generator.

Travis
npm
npm
npm

Highlights

  • Works on server and client
  • CLI utility
  • Save QR code as image
  • Support for Numeric, Alphanumeric, Kanji and Byte mode
  • Support for mixed modes
  • Support for chinese, cyrillic, greek and japanese characters
  • Support for multibyte characters (like emojis 😄)
  • Auto generates optimized segments for best data compression and smallest QR Code size

Installation

Inside your project folder do:

npm install --save qrcode

or, install it globally to use qrcode from the command line to save qrcode images or generate ones you can view in your terminal.

npm install -g qrcode

Usage

CLI

qrcode <text> [output file]

Output image format is detected from file extension.

Supported format are png, svg and txt.

If no output file is specified, the QR Code will be rendered directly in the terminal.

Example

qrcode "Draw a QR Code in my terminal"
qrcode "I like to save qrs as a PNG" qr.png
qrcode "I also like to save them as a SVG" qr.svg

Browser

node-qrcode can be used in browser through module bundlers like Browserify and Webpack or by including the precompiled bundle present in build/ folder.

Module bundlers

<!-- index.html -->
<html>
  <body>
    <canvas id="canvas"></canvas>
    <script src="bundle.js"></script>
  </body>
</html>
// index.js -> bundle.js
var QRCode = require('qrcode')
var canvas = document.getElementById('canvas')

QRCode.toCanvas(canvas, 'sample text', function (error) {
  if (error) console.error(error)
  console.log('success!');
})

Precompiled bundle

<canvas id="canvas"></canvas>

<script src="/build/qrcode.min.js"></script>
<script>
  qrcodelib.toCanvas(document.getElementById('canvas'), 'sample text', function (error) {
    if (error) console.error(error)
    console.log('success!');
  })
</script>

If you install through npm, precompiled files will be available in node_modules/qrcode/build/ folder.

NodeJS

Simply require the module qrcode

var QRCode = require('qrcode')

QRCode.toDataURL('I am a pony!', function (err, url) {
  console.log(url)
})

Error correction level

Error correction capability allows to successfully scan a QR Code even if the symbol is dirty or damaged.
Four levels are available to choose according to the operating environment.

Higher levels offer a better error resistance but reduce the symbol's capacity.

If the chances that the QR Code symbol may be corrupted are low (for example if it is showed through a monitor)
is possible to safely use a low error level such as Low or Medium.

Possible levels are shown below:

Level Error resistance
L (Low) ~7%
M (Medium) ~15%
Q (Quartile) ~25%
H (High) ~30%

The percentage indicates the maximum amount of damaged surface after which the symbol becomes unreadable.

Error level can be set through options.errorCorrectionLevel property.

If not specified, the default value is M.

QRCode.toDataURL('some text', { errorCorrectionLevel: 'H' }, function (err, url) {
  console.log(url)
})

QR Code capacity

Capacity depends on symbol version and error correction level. Also encoding modes may influence the amount of storable data.

The QR Code versions range from version 1 to version 40.

Each version has a different number of modules (black and white dots), which define the symbol's size.
For version 1 they are 21x21, for version 2 25x25 e so on.
Higher is the version, more are the storable data, and of course bigger will be the QR Code symbol.

The table below shows the maximum number of storable characters in each encoding mode and for each error correction level.

Mode L M Q H
Numeric 7089 5596 3993 3057
Alphanumeric 4296 3391 2420 1852
Byte 2953 2331 1663 1273
Kanji 1817 1435 1024 784

Note: Maximum characters number can be different when using Mixed modes.

QR Code version can be set through options.version property.

If no version is specified, the more suitable value will be used. Unless a specific version is required, this option is not needed.

QRCode.toDataURL('some text', { version: 2 }, function (err, url) {
  console.log(url)
})

Encoding modes

Modes can be used to encode a string in a more efficient way.

A mode may be more suitable than others depending on the string content.
A list of supported modes are shown in the table below:

Mode Characters Compression
Numeric 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 3 characters are represented by 10 bits
Alphanumeric 0–9, A–Z (upper-case only), space, $, %, *, +, -, ., /, : 2 characters are represented by 11 bits
Kanji Characters from the Shift JIS system based on JIS X 0208 2 kanji are represented by 13 bits
Byte Characters from the ISO/IEC 8859-1 character set Each characters are represented by 8 bits

Choose the right mode may be tricky if the input text is unknown.

In these cases Byte mode is the best choice since all characters can be encoded with it. (See Multibyte characters)

However, if the QR Code reader supports mixed modes, using Auto mode may produce better results.

Mixed modes

Mixed modes are also possible. A QR code can be generated from a series of segments having different encoding modes to optimize the data compression.

However, switching from a mode to another has a cost which may lead to a worst result if it's not taken into account.
See Manual mode for an example of how to specify segments with different encoding modes.

Auto mode

By default, automatic mode selection is used.

The input string is automatically splitted in various segments optimized to produce the shortest possible bitstream using mixed modes.

This is the preferred way to generate the QR Code.

For example, the string ABCDE12345678?A1A will be splitted in 3 segments with the following modes:

Segment Mode
ABCDE Alphanumeric
12345678 Numeric
?A1A Byte

Any other combinations of segments and modes will result in a longer bitstream.

If you need to keep the QR Code size small, this mode will produce the best results.

Manual mode

If auto mode doesn't work for you or you have specific needs, is also possible to manually specify each segment with the relative mode.
In this way no segment optimizations will be applied under the hood.

Segments list can be passed as an array of object:

  var QRCode = require('qrcode')

  var segs = [
    { data: 'ABCDEFG', mode: 'alphanumeric' },
    { data: '0123456', mode: 'numeric' }
  ]

  QRCode.toDataURL(segs, function (err, url) {
    console.log(url)
  })

Kanji mode

With kanji mode is possible to encode characters from the Shift JIS system in an optimized way.

Unfortunately, there isn't a way to calculate a Shifted JIS values from, for example, a character encoded in UTF-8, for this reason a conversion table from the input characters to the SJIS values is needed.

This table is not included by default in the bundle to keep the size as small as possible.

If your application requires kanji support, you will need to pass a function that will take care of converting the input characters to appropriate values.

An helper method is provided by the lib through an optional file that you can include as shown in the example below.

Note: Support for Kanji mode is only needed if you want to benefit of the data compression, otherwise is still possible to encode kanji using Byte mode (See Multibyte characters).

  var QRCode = require('qrcode')
  var toSJIS = require('qrcode/helper/to-sjis')

  QRCode.toDataURL(kanjiString, { toSJISFunc: toSJIS }, function (err, url) {
    console.log(url)
  })

With precompiled bundle:

<canvas id="canvas"></canvas>

<script src="/build/qrcode.min.js"></script>
<script src="/build/qrcode.tosjis.min.js"></script>
<script>
  qrcodelib.toCanvas(document.getElementById('canvas'),
    'sample text', { toSJISFunc: qrcodelib.toSJIS }, function (error) {
    if (error) console.error(error)
    console.log('success!')
  })
</script>

Multibyte characters

Support for multibyte characters isn't present in the initial QR Code standard, but is possible to encode UTF-8 characters in Byte mode.

QR Codes provide a way to specify a different type of character set through ECI (Extended Channel Interpretation), but it's not fully implemented in this lib yet.

Most QR Code readers, however, are able to recognize multibyte characters even without ECI.

Note that a single Kanji/Kana or Emoji can take up to 4 bytes.

API

Browser:

Server:

Browser API

create(text, [options])

Creates QR Code symbol and returns a qrcode object.

text

Type: String|Array

Text to encode or a list of objects describing segments.

options

See QR Code options.

returns

Type: Object

// QRCode object
{
  modules,              // Bitmatrix class with modules data
  version,              // Calculated QR Code version
  errorCorrectionLevel, // Error Correction Level
  maskPattern,          // Calculated Mask pattern
  segments              // Generated segments
}

toCanvas(canvasElement, text, [options], cb(error))

toCanvas(text, [options], cb(error, canvas))

Draws qr code symbol to canvas.

If canvasElement is omitted a new canvas is returned.

canvasElement

Type: DOMElement

Canvas where to draw QR Code.

text

Type: String|Array

Text to encode or a list of objects describing segments.

options

See Options.

cb

Type: Function

Callback function called on finish.

Example
QRCode.toCanvas('text', { errorCorrectionLevel: 'H' }, function (err, canvas) {
  if (err) throw err

  var container = document.getElementById('container')
  container.appendChild(canvas)
})

toDataURL(text, [options], cb(error, url))

toDataURL(canvasElement, text, [options], cb(error, url))

Returns a Data URI containing a representation of the QR Code image.

If provided, canvasElement will be used as canvas to generate the data URI.

canvasElement

Type: DOMElement

Canvas where to draw QR Code.

text

Type: String|Array

Text to encode or a list of objects describing segments.

options
  • type

    Type: String

    Default: image/png

    Data URI format.

    Possible values are: image/png, image/jpeg, image/webp.

    Note: image/webp only works in Chrome browser.

  • rendererOpts.quality

    Type: Number

    Default: 0.92

    A Number between 0 and 1 indicating image quality if the requested type is image/jpeg or image/webp.

See Options for other settings.

cb

Type: Function

Callback function called on finish.

Example
var opts = {
  errorCorrectionLevel: 'H',
  type: 'image/jpeg',
  rendererOpts: {
    quality: 0.3
  }
}

QRCode.toDataURL('text', opts, function (err, url) {
  if (err) throw err

  var img = document.getElementById('image')
  img.src = url
})

Server API

create(text, [options])

See create.


toCanvas(canvas, text, [options], cb(error))

Draws qr code symbol to node canvas.

text

Type: String|Array

Text to encode or a list of objects describing segments.

options

See Options.

cb

Type: Function

Callback function called on finish.


toDataURL(text, [options], cb(error, url))

Returns a Data URI containing a representation of the QR Code image.

Only works with image/png type for now.

text

Type: String|Array

Text to encode or a list of objects describing segments.

options

See Options for other settings.

cb

Type: Function

Callback function called on finish.


toString(text, [options], cb(error, string))

Returns a string representation of the QR Code.

If choosen output format is svg it will returns a string containing xml code.

text

Type: String|Array

Text to encode or a list of objects describing segments.

options
  • type

    Type: String

    Default: utf8

    Output format.

    Possible values are: utf8, svg, terminal.

See Options for other settings.

cb

Type: Function

Callback function called on finish.

Example
QRCode.toString('http://www.google.com', function (err, string) {
  if (err) throw err
  console.log(string)
})

toFile(path, text, [options], cb(error))

Saves QR Code to image file.

If options.type is not specified, the format will be guessed from file extension.

Recognized extensions are png, svg, txt.

path

Type: String

Path where to save the file.

text

Type: String|Array

Text to encode or a list of objects describing segments.

options
  • type

    Type: String

    Default: png

    Output format.

    Possible values are: png, svg, utf8.

  • rendererOpts.deflateLevel (png only)

    Type: Number

    Default: 9

    Compression level for deflate.

  • rendererOpts.deflateStrategy (png only)

    Type: Number

    Default: 3

    Compression strategy for deflate.

See Options for other settings.

cb

Type: Function

Callback function called on finish.

Example
QRCode.toFile('path/to/filename.png', 'Some text', {
  color: {
    dark: '#00F',  // Blue dots
    light: '#0000' // Transparent background
  }
}, function (err) {
  if (err) throw err
  console.log('done')
})

toFileStream(stream, text, [options], cb(error))

Writes QR Code image to stream. Only works with png format for now.

stream

Type: stream.Writable

Node stream.

text

Type: String|Array

Text to encode or a list of objects describing segments.

options

See Options.

cb

Type: Function

Callback function called on finish.


Options

QR Code options

version

Type: Number

QR Code version. If not specified the more suitable value will be calculated.

errorCorrectionLevel

Type: String

Default: M

Error correction level.

Possible values are low, medium, quartile, high or L, M, Q, H.

toSJISFunc

Type: Function

Helper function used internally to convert a kanji to its Shift JIS value.

Provide this function if you need support for Kanji mode.

Renderers options

margin

Type: Number

Default: 4

Define how much wide the quiet zone should be.

scale

Type: Number

Default: 4

Scale factor. A value of 1 means 1px per modules (black dots).

color.dark

Type: String

Default: #000000ff

Color of dark module. Value must be in hex format (RGBA).

Note: dark color should always be darker than color.light.

color.light

Type: String

Default: #ffffffff

Color of light module. Value must be in hex format (RGBA).


GS1 QR Codes

There was a real good discussion here about them. but in short any qrcode generator will make gs1 compatible qrcodes, but what defines a gs1 qrcode is a header with metadata that describes your gs1 information.

soldair/node-qrcode#45

Credits

This lib is based on "QRCode for JavaScript" which Kazuhiko Arase thankfully MIT licensed.

License

MIT

The word "QR Code" is registered trademark of:

DENSO WAVE INCORPORATED
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