tesseract.js/README.md

> # UNDER CONTRUCTION
> ## Due for Release on Monday, Oct 3, 2016

# tesseract.js
Tesseract.js is a pure javascript version of the Tesseract OCR Engine that can recognize English, Chinese, Russian, and 60 other languages.

<!-- ![alt text]( "Logo Title Text 1") -->

# 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

```html
<script src='https://cdn.rawgit.com/naptha/tesseract.js/5ed4c0bc/dist/tesseract.js'></script>

<script>
var worker = createTesseractWorker('https://cdn.rawgit.com/naptha/tesseract.js/5ed4c0bc/dist/tesseract.worker.js')

worker.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](https://github.com/naptha/tesseract.js/tree/master/dist). Then include `tesseract.js` on your page like this:


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

<script>
var worker = createTesseractWorker('/path/to/tesseract.worker.js')

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


## npm
### TODO

<!-- ```shell
> npm install tesseract-js ?
```-->

# Docs
## Tesseract.recognize(image) -> [TesseractJob](#tesseractjob)
Returns a TesseractJob whose `then` method can be used to act on the result of the OCR.

For example:

`image` can 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 :(
 - 

## Tesseract.detect(image) -> [TesseractJob](#tesseractjob)
Returns a TesseractJob whose `then` method can be used to act on the result of the OCR.

For example:

`image` can 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 TesseractJob return itself to enable chaining. 

Typical use is: 
```javascript
var job1 = Tesseract.recognize('#my-image')

job1.progress(function(message){console.log(message)})
    .error(function(err){console.error(err)})
    .then(function(result){console.log(result)})
```

or more concisely:
```javascript
Tesseract.recognize('#my-image')
    .progress(function(message){console.log(message)})
    .error(function(err){console.error(err)})
    .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 json object.

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

The console will show something like: 
```javascript
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. 

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

The console will show something like: 
```javascript
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 and when the job successfully completes. 


# Contributing
## Development
To run a development copy of tesseract.js, first clone this repo.
```shell
> git clone https://github.com/naptha/tesseract.js.git
```

Then, cd in to the folder, `npm install`, and `npm start`
```shell
> 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](#development), you can build static library files in the dist folder with 
```shell
> npm run build
```

## Send us a Pull Request!