tesseract.js/docs/api.md

API

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

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

Note: image should be sufficiently high resolution. Often, the same image will get much better results if you upscale it before calling recognize.

• image see Image Format for more details.
• lang property with a value from the list of lang parameters, you can use multiple languages separated by '+', ex. eng+chi_tra
• options a flat json object that may include properties that override some subset of the default tesseract parameters

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

Simple Example:

const worker = new Tessearct.TesseractWorker();
worker
  .recognize(myImage)
  .then(function(result){
    console.log(result);
  });

More Complicated Example:

const worker = new Tessearct.TesseractWorker();
// if we know our image is of spanish words without the letter 'e':
worker
  .recognize(myImage, 'spa', {
    tessedit_char_blacklist: 'e',
  })
  .then(function(result){
    console.log(result);
  });

Tesseract.detect(image) -> TesseractJob

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

• image see Image Format for more details.

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

const worker = new Tessearct.TesseractWorker();
worker
  .detect(myImage)
  .then(function(result){
    console.log(result);
  });

TesseractJob

A TesseractJob is an object returned by a call to recognize or detect. It's inspired by the ES6 Promise interface and provides then and catch methods. It also provides finally method, which will be fired regardless of the job fate. One important difference is that these methods return the job itself (to enable chaining) rather than new.

Typical use is:

const worker = new Tessearct.TesseractWorker();
worker.recognize(myImage)
  .progress(message => console.log(message))
  .catch(err => console.error(err))
  .then(result => console.log(result))
  .finally(resultOrError => console.log(resultOrError));

Which is equivalent to:

const worker = new Tessearct.TesseractWorker();
const job1 = worker.recognize(myImage);

job1.progress(message => console.log(message));

job1.catch(err => console.error(err));

job1.then(result => console.log(result));

job1.finally(resultOrError => console.log(resultOrError));

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:

const worker = new Tessearct.TesseractWorker();
worker.recognize(myImage)
  .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:

const worker = new Tessearct.TesseractWorker();
worker.recognize(myImage)
  .then(function(result){console.log('result is: ', result)});

The console will show something like:

result 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.catch(callback: function) -> TesseractJob

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

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

TesseractJob.finally(callback: function) -> TesseractJob

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

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