UNDER CONTRUCTION

Due for Release on Monday, Oct 3, 2016

Tesseract.js

Installation • Docs • Contributing

Tesseract.js is a pure javascript library that lets you get words written in English, Chinese, Russian, and 60 other languages, out of scanned documents and other images. More specifically, Tesseract.js is a wrapper around an emscripten port of the Tesseract OCR Engine.

Installation

Tesseract.js works with a <script> tag via local copy or cdn, or with npm (if you're using webpack / browserify).

Script Tag

CDN

<script src='https://cdn.rawgit.com/naptha/tesseract.js/a01d2a2/dist/tesseract.js'></script>

<script>
Tesseract.recognize('#my-image')
    .progress(function (p) { console.log('progress', p) })
    .then(function (result) { console.log('result', result) })
</script>

Local

First grab copies of tesseract.js and tesseract.worker.js from the dist folder. Then include tesseract.js on your page, and set Tesseract.workerUrl like this:

<script src='/path/to/tesseract.js'></script>

<script>
Tesseract.workerUrl = 'http://www.absolute-path-to/tesseract.worker.js'

Tesseract.recognize('#my-image')
    .progress(function (p) { console.log('progress', p) })
    .then(function (result) { console.log('result', result) })
</script>

npm

TODO

walp

Docs

• [Tesseract.recognize(image: ImageLike[, options]) -> TesseractJob](#tesseractrecognizeimage-imagelike-options---tesseractjob)
  • Simple Example
  • More Complicated Example
• [Tesseract.detect(image: ImageLike) -> TesseractJob](#tesseractdetectimage-imagelike---tesseractjob)
• ImageLike
• TesseractJob
  • TesseractJob.progress(callback: function) -> TesseractJob
  • TesseractJob.then(callback: function) -> TesseractJob
  • TesseractJob.error(callback: function) -> TesseractJob
• Tesseract Remote File Options
  • Tesseract.coreUrl
  • Tesseract.workerUrl
  • Tesseract.langUrl

Tesseract.recognize(image: ImageLike[, options]) -> TesseractJob

Figures out what words are in image, where the words are in image, etc.

• image is any ImageLike object.
• options is an optional flat json object. options may:
  • include properties that override some subset of the default tesseract parameters
  • include a lang property with a value from the list of lang parameters

Returns a TesseractJob whose then, progress, and error methods can be used to act on the result.

Simple Example:

Tesseract.recognize('#my-image')
.then(function(result){
    console.log(result)
})

More Complicated Example:

// if we know our image is of spanish words without the letter 'e':
Tesseract.recognize('#my-image', {
    lang: 'spa',
    tessedit_char_blacklist: 'e'
})
.then(function(result){
    console.log(result)
})

Tesseract.detect(image: ImageLike) -> TesseractJob

Figures out what script (e.g. 'Latin', 'Chinese') the words in image are written in.

• image is any ImageLike object.

Returns a TesseractJob whose then, progress, and error methods can be used to act on the result of the script.

Tesseract.detect('#my-image')
.then(function(result){
    console.log(result)
})

ImageLike

The main Tesseract.js functions take an image parameter, which should be something that is 'image-like'. That means image should be

• an img element or querySelector that matches an img element
• a video element or querySelector that matches a video element
• a canvas element or querySelector that matches a canvas element
• a CanvasRenderingContext2D (returned by canvas.getContext('2d'))
• the absolute url of an image from the same website that is running your script. Browser security policies don't allow access to the content of images from other websites :(

TesseractJob

A TesseractJob is an an object returned by a call to recognize or detect. All methods of a given TesseractJob return that TesseractJob to enable chaining.

Typical use is:

Tesseract.recognize('#my-image')
    .progress(function(message){console.log(message)})
    .error(function(err){console.error(err)})
    .then(function(result){console.log(result)})

Which is equivalent to:

var job1 = Tesseract.recognize('#my-image');

job1.progress(function(message){console.log(message)});

job1.error(function(err){console.error(err)});

job1.then(function(result){console.log(result)})

TesseractJob.progress(callback: function) -> TesseractJob

Sets callback as the function that will be called every time the job progresses.

• callback is a function with the signature callback(progress) where progress is a json object.

For example:

Tesseract.recognize('#my-image')
    .progress(function(message){console.log('progress is: 'message)})

The console will show something like:

progress is: {loaded_lang_model: "eng", from_cache: true}
progress is: {initialized_with_lang: "eng"}
progress is: {set_variable: Object}
progress is: {set_variable: Object}
progress is: {recognized: 0}
progress is: {recognized: 0.3}
progress is: {recognized: 0.6}
progress is: {recognized: 0.9}
progress is: {recognized: 1}

TesseractJob.then(callback: function) -> TesseractJob

Sets callback as the function that will be called if and when the job successfully completes.

• callback is a function with the signature callback(result) where result is a json object.

For example:

Tesseract.recognize('#my-image')
    .then(function(result){console.log('result is: 'result)})

The console will show something like:

progress is: {
    blocks: Array[1]
    confidence: 87
    html: "<div class='ocr_page' id='page_1' ..."
    lines: Array[3]
    oem: "DEFAULT"
    paragraphs: Array[1]
    psm: "SINGLE_BLOCK"
    symbols: Array[33]
    text: "Hello World↵from beyond↵the Cosmic Void↵↵"
    version: "3.04.00"
    words: Array[7]
}

TesseractJob.error(callback: function) -> TesseractJob

Sets callback as the function that will be called if the job fails.

• callback is a function with the signature callback(erros) where error is a json object.

Tesseract Remote File Options

Tesseract.coreUrl

A string specifying the location of the tesseract.js-core library, with default value 'https://cdn.rawgit.com/naptha/tesseract.js-core/master/index.js'. Set this string before calling Tesseract.recognize and Tesseract.detect if you want Tesseract.js to use a different file.

For example:

Tesseract.coreUrl = 'https://absolute-path-to/tesseract.js-core/index.js'

Tesseract.workerUrl

A string specifying the location of the tesseract.worker.js file, with default value 'https://cdn.rawgit.com/naptha/tesseract.js/8b915dc/dist/tesseract.worker.js'. Set this string before calling Tesseract.recognize and Tesseract.detect if you want Tesseract.js to use a different file.

For example:

Tesseract.workerUrl = 'https://absolute-path-to/tesseract.worker.js'

Tesseract.langUrl

A string specifying the location of the tesseract language files, with default value 'https://cdn.rawgit.com/naptha/tessdata/gh-pages/3.02/'. Language file urls are calculated according to the formula Tesseract.langUrl + lang + '.traineddata.gz'. Set this string before calling Tesseract.recognize and Tesseract.detect if you want Tesseract.js to use different language files.

In the following exampple, Tesseract.js will download the language file from 'https://absolute-path-to/lang/folder/rus.traineddata.gz':

Tesseract.langUrl = 'https://absolute-path-to/lang/folder/'

Tesseract.recognize('#my-im', {
    lang: 'rus'
})

Contributing

Development

To run a development copy of tesseract.js, first clone this repo.

> git clone https://github.com/naptha/tesseract.js.git

Then, cd in to the folder, npm install, and npm start

> cd tesseract.js
> npm install && npm start

  ... a bunch of npm stuff ... 

  tesseract.js@1.0.0 start /Users/guillermo/Desktop/code_static/tesseract.js
  node devServer.js

Listening at http://localhost:7355

Then open http://localhost:7355 in your favorite browser. The devServer automatically rebuilds tesseract.js and tesseract.worker.js when you change files in the src folder.

Building Static Files

After you've cloned the repo and run npm install as described in the Development Section, you can build static library files in the dist folder with

> npm run build

Send us a Pull Request!

Thanks :)