Cordova Tesseract-OCR Plugin - For Android and iOS

This is a Cordova/Ionic plugin for OCR process using Tesseract library for both Android and iOS. Tesseract is an Open Source library for OCR (Optical Character Recognition) process.

This plugin defines a global TesseractPlugin object, which provides an API for recognizing text on images.

  TesseractPlugin.recognizeText(imageData, language, function(recognizedText) {
    deferred.resolve(recognizedText);
  }, function(reason) {
    deferred.reject('Error on recognizing text from image. ' + reason);
  });

Installation

Before installing this plugin, make sure you have added the platform for your app:

$ ionic platform add android

-> substitute android with ios to build for iOS.

1. Download or clone this project, copy it to your app root folder and run ionic command to add the plugin:

$ git clone https://github.com/gustavomazzoni/cordova-plugin-tesseract
$ cp -rf cordova-plugin-tesseract your-project/cordova-plugin-tesseract
$ cd your-project/
$ ionic plugin add cordova-plugin-tesseract

2. For Android platform:

2.1 Download or clone tess-two project (it contains Tesseract library for Android) and copy the 'tess-two' folder inside of it to your android platform:

$ git clone https://github.com/rmtheis/tess-two
$ cp -rf tess-two/tess-two/ your-project/platforms/android/tess-two

2.2 Edit your-project/platforms/android/tess-two/build.gradle and replace all content with:

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.14.0'
    }
}

apply plugin: 'android-library'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.2"

    defaultConfig {
        minSdkVersion 8
        targetSdkVersion 23
    }

    sourceSets.main {
        manifest.srcFile 'AndroidManifest.xml'
        java.srcDirs = ['src']
        resources.srcDirs = ['src']
        res.srcDirs = ['res']
        jniLibs.srcDirs = ['libs']
    }
}

2.3 Edit your-project/platforms/android/build.gradle file and add 'tess-two' as a dependency to your project (after // SUB-PROJECT DEPENDENCIES END line):

dependencies {
    compile fileTree(dir: 'libs', include: '*.jar')
    // SUB-PROJECT DEPENDENCIES START
    debugCompile project(path: "CordovaLib", configuration: "debug")
    releaseCompile project(path: "CordovaLib", configuration: "release")
    // SUB-PROJECT DEPENDENCIES END
    compile project(':tess-two')
}

2.4 Edit your-project/platforms/android/cordova/lib/build.js file that generates settings.gradle file:

• Edit your-project/platforms/android/cordova/lib/builders/GradleBuilder.js and replace the fs.writeFileSync() function call after // Write the settings.gradle file. (at line 101) with:

//##### EDITED - Added tess-two library dependency
fs.writeFileSync(path.join(this.root, 'settings.gradle'),
    '// GENERATED FILE - DO NOT EDIT\n' +
    'include ":"\n' + settingsGradlePaths.join('') +
    'include ":tess-two"');

2.5 Your project is ready to use this plugin on Android platform. Build your project:

$ ionic build android

3. For iOS platform:

3.1 Inside root directory of your ios platform, create Podfile and add Tesseract OCR iOS (Tesseract library for iOS7+) as a dependency:

• Create your-project/platforms/ios/Podfile
• Add 'TesseractOCRiOS' dependency (replace 'ocr-translation' with the name of your project):

source 'https://github.com/CocoaPods/Specs.git'
xcodeproj 'ocr-translation.xcodeproj/'

target 'ocr-translation' do

	pod 'TesseractOCRiOS', '4.0.0'

end

3.2 Still at your ios platform folder, install the dependencies (install the CocoaPods in case you don't have it yet) using the following commands:

$ pod install

3.3 Your project is ready to use this plugin on iOS platform. Build your project:

$ ionic build ios

Your project is ready to use this plugin.

Usage

cordova-plugin-tesseract is designed to recognize text in images in many languages, but for that to work we need to have the tessdata of the language you want the text to be recognized.

To use this plugin and recognize text in images, you need to:

1. Download the language

As soon as you enter on your OCR use case, call TesseractPlugin.loadLanguage function to download the tessdata for your language:

TesseractPlugin.loadLanguage(language, function(response) {
  deferred.resolve(response);
}, function(reason) {
  deferred.reject('Error on loading OCR file for your language. ' + reason);
});

2. Get image data from your photo

Load the image you want the text to be recognized from. On your angular Controller use $cordovaCamera or cordova-plugin-camera plugin to take the photo or load an image:

$cordovaCamera.getPicture(options).then(function(imageData) {
  $scope.image = "data:image/jpeg;base64," + imageData;
  $scope.text = null;

  $timeout(function() {
    // DOM has finished rendering
    // insert here the call to TesseractPlugin.recognizeText function to recognize the text
    
  });
}, function(err) {
  // error
  console.log('ERROR with camera plugin. Error: ' + err);
});

3. Recognize text from image

Then, after loaded the image, just call TesseractPlugin.recognizeText function with the image data, the language of the text in the image and a callback function to be called after the operation is done.

TesseractPlugin.recognizeText(imageData, language, function(recognizedText) {
  $scope.text = recognizedText;
}, function(reason) {
  console.log('Error on recognizing text from image. ' + reason);
});