# node-qrcode
> QR code/2d barcode generator.
[](http://travis-ci.org/soldair/node-qrcode)
[](https://www.npmjs.com/package/qrcode)
[](https://www.npmjs.com/package/qrcode)
[](https://github.com/soldair/node-qrcode/blob/master/license)
- [Highlights](#highlights)
- [Installation](#installation)
- [Usage](#usage)
- [Error correction level](#error-correction-level)
- [QR Code capacity](#qr-code-capacity)
- [Encoding Modes](#encoding-modes)
- [Binary data](#binary-data)
- [Multibyte characters](#multibyte-characters)
- [API](#api)
- [GS1 QR Codes](#gs1-qr-codes)
- [Credits](#credits)
- [License](#license)
## Highlights
- Works on server and client (and react native with svg)
- 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 :smile:)
- Auto generates optimized segments for best data compression and smallest QR Code size
- App agnostic readability, QR Codes by definition are app agnostic
## Installation
Inside your project folder do:
```shell
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.
```shell
npm install -g qrcode
```
## Usage
### CLI
```
Usage: qrcode [options] <input string>
QR Code options:
-v, --qversion QR Code symbol version (1 - 40) [number]
-e, --error Error correction level [choices: "L", "M", "Q", "H"]
-m, --mask Mask pattern (0 - 7) [number]
Renderer options:
-t, --type Output type [choices: "png", "svg", "utf8"]
-w, --width Image width (px) [number]
-s, --scale Scale factor [number]
-q, --qzone Quiet zone size [number]
-l, --lightcolor Light RGBA hex color
-d, --darkcolor Dark RGBA hex color
--small Output smaller QR code to terminal [boolean]
Options:
-o, --output Output file
-h, --help Show help [boolean]
--version Show version number [boolean]
Examples:
qrcode "some text" Draw in terminal window
qrcode -o out.png "some text" Save as png image
qrcode -d F00 -o out.png "some text" Use red as foreground color
```
If not specified, output type is guessed from file extension.<br>
Recognized extensions are `png`, `svg` and `txt`.
### Browser
`node-qrcode` can be used in browser through module bundlers like [Browserify](https://github.com/substack/node-browserify) and [Webpack](https://github.com/webpack/webpack) or by including the precompiled bundle present in `build/` folder.
#### Module bundlers
```html
<!-- index.html -->
<html>
<body>
<canvas id="canvas"></canvas>
<script src="bundle.js"></script>
</body>
</html>
```
```javascript
// 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
```html
<canvas id="canvas"></canvas>
<script src="/build/qrcode.js"></script>
<script>
QRCode.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.
The precompiled bundle have support for [Internet Explorer 10+, Safari 5.1+, and all evergreen browsers](https://browserl.ist/?q=defaults%2C+IE+%3E%3D+10%2C+Safari+%3E%3D+5.1).
### NodeJS
Require the module `qrcode`
```javascript
var QRCode = require('qrcode')
QRCode.toDataURL('I am a pony!', function (err, url) {
console.log(url)
})
```
render a qrcode for the terminal
```js
var QRCode = require('qrcode')
QRCode.toString('I am a pony!',{type:'terminal'}, function (err, url) {
console.log(url)
})
```
### ES6/ES7
Promises and Async/Await can be used in place of callback function.
```javascript
import QRCode from 'qrcode'
// With promises
QRCode.toDataURL('I am a pony!')
.then(url => {
console.log(url)
})
.catch(err => {
console.error(err)
})
// With async/await
const generateQR = async text => {
try {
console.log(await QRCode.toDataURL(text))
} catch (err) {
console.error(err)
}
}
```
## 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.<br>
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.<br>
If not specified, the default value is `M`.
```javascript
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**.<br>
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](#mixed-modes).
QR Code version can be set through `options.version` property.<br>
If no version is specified, the more suitable value will be used. Unless a specific version is required, this option is not needed.
```javascript
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.<br>
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, $, %, *, +, -, ., /, : |
win10系统 64位 ffmpeg、node等技术 实现视频的转换
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