quaggaJS/README.md

quaggaJS

• Changelog (2015-03-12)

QuaggaJS is a barcode-scanner entirely written in JavaScript supporting real-time localization and decoding of various types of barcodes such as EAN and CODE128. The library is also capable of using getUserMedia to get direct access to the user's camera stream. Although the code relies on heavy image-processing even recent smartphones are capable of locating and decoding barcodes in real-time.

Try some examples and check out the blog post (How barcode-localization works in QuaggaJS) if you want to dive deeper into this topic.

Yet another barcode library?

This is not yet another port of the great zxing library, but more of an extension to it. This implementation features a barcode locator which is capable of finding a barcode-like pattern in an image resulting in an estimated bounding box including the rotation. Simply speaking, this reader is invariant to scale and rotation, whereas other libraries require the barcode to be aligned with the viewport.

Requirements

In order to take full advantage of quaggaJS, the browser needs to support the getUserMedia API which is already implemented in recent versions of Firefox, Chrome and Opera. The API is also available on their mobile counterparts installed on Android. Safari and IE do not allow the access to the camera yet, neither on desktop, nor on mobile. You can check caniuse for updates.

In cases where real-time decoding is not needed, or the platform does not support getUserMedia QuaggaJS is also capable of decoding image-files using the File API or other URL sources.

Installation

Just clone the repository and include dist/quagga.js in your project. You can also build the library yourself by simply typing:

> npm install
> grunt

Minification

Currently, I strongly disapprove using grunt uglify since it does not handle asm.js code correctly (see issue). The resulting code still works, but the performance might suffer, especially in Firefox. Additionally it triggers some ugly log-warnings in the console.

This is how you create a minified version of quaggaJS (saved in dist/quagga.min.js):

> grunt uglify

Special care has to be taken if a minimized/uglified version of the code is needed. Basically the grunt task grunt uglify takes the dist/quagga.js as input and saves the minified code in dist/quagga.min.js. Since the introduction of web-workers in quaggaJS, the filename of the script is important, because the instantiation of the workers rely on it. This script-name defaults to quagga.js and can be changed in the config with the key config.scriptName. The supplied string must match the filename of the file being served by the webserver. Now, in the case of a minified version, the config must be adapted so that config.scriptName points to quagga.min.js.

See the config for all supported options.

Usage

You can check out the examples to get an idea of how to use QuaggaJS. Basically the library exposes the following API:

Quagga.init(config, callback)

This method initializes the library for a given configuration config (see below) and invokes the callback when Quagga is ready to start. The initialization process also requests for camera access if real-time detection is configured.

Quagga.init({
    inputStream : {
      name : "Live",
      type : "LiveStream"
    },
    decoder : {
      readers : ["code_128_reader"]
    }
  }, function() {
      console.log("Initialization finished. Ready to start");
      Quagga.start();
  });

Quagga.start()

When the library is initialized, the start() method starts the video-stream and begins locating and decoding the images.

Quagga.stop()

If the decoder is currently running, after calling stop() the decoder does not process any more images. Additionally, if a camera-stream was requested upon initialization, this operation also disconnects the camera.

Quagga.onProcessed(callback)

This method registers a callback(data) function that is called for each frame after the processing is done. The data object contains detailed information about the success/failure of the operation. The output varies, depending whether the detection and/or decoding were successful or not.

Quagga.onDetected(callback)

Registers a callback(data) function which is triggered whenever a barcode-pattern has been located and decoded successfully. The passed data object contains information about the decoding process including the detected code which can be obtained by calling data.codeResult.code.

Quagga.decodeSingle(config, callback)

In contrast to the calls described above, this method does not rely on getUserMedia and operates on a single image instead. The provided callback is the same as in onDetected and contains the result data object.

The result object

The callbacks passed into onProcessed, onDetected and decodeSingle receive a data object upon execution. The data object contains the following information. Depending on the success, some fields may be undefined or just empty.

{
  "codeResult": {
    "code": "FANAVF1461710",
    "start": 355,
    "end": 26,
    "codeset": 100,
    "startInfo": {
      "error": 1.0000000000000002,
      "code": 104,
      "start": 21,
      "end": 41
    },
    "decodedCodes": [{
      "code": 104,
      "start": 21,
      "end": 41
    },
    // stripped for brevity
    {
      "error": 0.8888888888888893,
      "code": 106,
      "start": 328,
      "end": 350
    }],
    "endInfo": {
      "error": 0.8888888888888893,
      "code": 106,
      "start": 328,
      "end": 350
    },
    "direction": -1
  },
  "line": [{
    "x": 25.97278706156836,
    "y": 360.5616435369468
  }, {
    "x": 401.9220519377024,
    "y": 70.87524989906444
  }],
  "angle": -0.6565217179979483,
  "pattern": [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, /* ... */ 1],
  "box": [
    [77.4074243622672, 410.9288668804402],
    [0.050203235235130705, 310.53619724086366],
    [360.15706727788256, 33.05711026051813],
    [437.5142884049146, 133.44977990009465]
  ],
  "boxes": [
    [
      [77.4074243622672, 410.9288668804402],
      [0.050203235235130705, 310.53619724086366],
      [360.15706727788256, 33.05711026051813],
      [437.5142884049146, 133.44977990009465]
    ],
    [
      [248.90769330706507, 415.2041489551161],
      [198.9532321622869, 352.62160512937635],
      [339.546160777576, 240.3979259789976],
      [389.5006219223542, 302.98046980473737]
    ]
  ]
}

Config

The default config object is set as followed:

{
  inputStream: { name: "Live",
       type: "LiveStream",
       constraints: {
         width: 640,
         height: 480,
         facing: "environment"
       }
  },
  tracking: false,
  debug: false,
  controls: false,
  locate: true,
  numOfWorkers: 4,
  scriptName: 'quagga.js',
  visual: {
    show: true
  },
  decoder:{
    drawBoundingBox: false,
    showFrequency: false,
    drawScanline: true,
    showPattern: false,
    readers: [
      'code_128_reader'
    ]
  },
  locator: {
    halfSample: true,
    showCanvas: false,
    showPatches: false,
    showFoundPatches: false,
    showSkeleton: false,
    showLabels: false,
    showPatchLabels: false,
    showRemainingPatchLabels: false,
    boxFromPatches: {
      showTransformed: false,
      showTransformedBox: false,
      showBB: false
    }
  }
}

Examples

The following example takes an image src as input and prints the result on the console. The decoder is configured to detect Code128 barcodes and enables the locating-mechanism for more robust results.

Quagga.decodeSingle({
  readers: ['code_128_reader'],
  locate: true, // try to locate the barcode in the image
  src: '/test/fixtures/code_128/image-001.jpg' // or 'data:image/jpg;base64,' + data
}, function(result){
  console.log(result);
});

Tests

Unit Tests can be run with Karma and written using Mocha, Chai and SinonJS. Coverage reports are automatically generated in the coverage/ folder.

> npm install
> grunt test

Image Debugging

In case you want to take a deeper dive into the inner workings of Quagga, get to know the debugging capabilities of the current implementation. The various flags exposed through the config object give you the abilily to visualize almost every step in the processing. Because of the introduction of the web-workers, and their restriction not to have access to the DOM, the configuration must be explicitly set to config.numOfWorkers = 0 in order to work.

Changelog

2015-03-12

• Improvements
  • removed dependency on async.js

2015-03-04

• Features
  • Added support for Code 39 barcodes

2015-01-21

• Features
  • Added support for web-worker (using 4 workers as default, can be changed through config.numOfWorkers)
  • Due to the way how web-workers are created, the name of the script file (config.scriptName) should be kept in sync with your actual filename
  • Removed canvas-overlay for decoding (boxes & scanline) which can now be easily implemented using the existing API (see example)
• API Changes In the course of implementing web-workers some breaking changes were introduced to the API.
  • The Quagga.init function no longer receives the callback as part of the config but rather as a second argument: Quagga.init(config, cb)
  • The callback to Quagga.onDetected now receives an object containing much more information in addition to the decoded code. (see data)
  • Added Quagga.onProcessed(callback) which provides a way to get information for each image processed. The callback receives the same data object as Quagga.onDetected does. Depending on the success of the process the data object might not contain any resultCode and/or box properties.