DavidStrausz / cordova-plugin-live-ocr

A cordova plugin which provides live ocr scanning capabilities for Android and iOS using Tesseract

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Cordova plugin for live OCR recognition using native Tesseract library - For Android and iOS

Installation:

  • git clone https://github.com/DavidStrausz/cordova-plugin-live-ocr.git
  • ionic plugin add cordova-plugin-live-ocr
  • ionic platform remove <platform>
  • ionic platform add <platform>

Integration in Ionic 2 project

Create a Native Wrapper:

  • Create ionic native wrapper for plugin
import { Cordova, Plugin } from 'ionic-native';

@Plugin({
  pluginName: 'LiveOcrPlugin',
  plugin: 'cordova-plugin-live-ocr',
  pluginRef: 'LiveOcrPlugin',
  repo: 'https://github.com/DavidStrausz/cordova-plugin-live-ocr',
  platforms: ['Android', 'iOS']
})
export class LiveOcrPlugin {
  @Cordova()
  static recognizeText(successCallback, errorCallback): Promise<any> { return; }

  @Cordova()
  static loadLanguage(language, successCallback, errorCallback): any { }
}

Usage in project

  • loadLanguage() is only required in android case, iOS version has a tessdata file integrated
import {LiveOcrPlugin} from 'path/to/native/wrapper/LiveOcrPlugin';
this.platform.ready().then(() => {
    //load language file for android (it is included for ios)
        LiveOcrPlugin.loadLanguage(
    'eng', 
    (success) => {
        //success callback
    },
    (error) => {
        //error callback
    });

    //start recognition process
    LiveOcrPlugin.recognizeText(
    (success) => {
        //success callback
    },
    (error) => {
        //error callback
    });
});

Important Notes:

  • when developing on different environments: remove platforms, remove cordova-plugin-live-ocr, install the plugin again, add platforms - otherwise the dependencies of cordova-plugin-live-ocr will be missing
  • in general: if something unexpected happens - remove plugin, readd plugin, remove platform, readd platform

iOS:

DEV-requirements:

  • Cocoapods must be set up (master repository)

    • TesseractOCRiOS cocoapod is added on plugin installation
  • Since iOS 10 it's mandatory to add a NSCameraUsageDescription and NSPhotoLibraryUsageDescription in the info.plist.

    • NSCameraUsageDescription describes the reason that the app accesses the user’s camera.
    • NSPhotoLibraryUsageDescription describes the reason the app accesses the user's photo library.
    • When the system prompts the user to allow access, this string is displayed as part of the dialog box.
    • This is done automatically when the plugin is installed
  • Optional when errors with bitcode occur while building:

    • Open workspace project in platforms/ios:
    • Project Pods -> Targets TesseractOCRiOS -> Build Settings -> Select All -> Search for bitcode -> Enable Bitcode No

How to modify and build:

Modify and build:

  • Following files, located in cordova-plugin-live-ocr/src/ios can be modified (header and implementation):
    • AROverlayViewController
    • CaptureSessionManager
    • LiveOcrPlugin
  • Readd the plugin
  • Build

Android:

Basic changes can be done in these two files located in cordova-plugin-live-ocr/src/android:

  • LiveOcrPlugin.java
  • OcrActivity.java

Changes which regard the camera view or the tesseract library can be done as follows:

Tess-two library:
  • If you don't want to use precompiled and built tess-two.aar:
    • Download Android NDK and add to Path
    • Download or clone tess-two project (it contains Tesseract library for Android)
    • Compile tess-two using android ndk
      -change to path/to/tess-two in terminal
      -enter ndk-build (this takes a while, go drink a coffee)
    • Add the library to a android studio project
    • Build the project
    • New .aar file can be copied from project-folder/tess-two/build/outputs/aar
Camera view:
  • Download or clone fork of android-ocr
  • Open android project
    • Open Android Studio
    • Select import existing project
    • Select platforms/android
  • Android Studio maybe complains about a few things (deprecated ndk use etc.)
  • Delete the jnilibs included by the plugin in Android Studio: android/jniLibs/* (only needed for builds)
  • Open build.gradle (Module: android)
    • Delete following line: apply from: "cordova-plugin-live-ocr/<appid>-libs.gradle"
  • Include OCRTest (from previously cloned android-ocr fork) project as module in android project (select gradle project)
  • Open OcrActivity.java (android/java/at.ventocom.liveocr.OcrActivity)
  • Click into the red colored CaptureActivity and hit alt + enter to add a dependency on previously included OCRTest project
  • When done modifying, build the project, copy platforms/android/OCRTest/build/outputs/aar/OCRTest-release.aar and replace the existing one in cordova-plugin-live-ocr/lib (don't forget to rename)

Finally:

  • Remove the plugin, readd the plugin, remove android platform, readd platform
  • Rebuild

TODO:

  • Test on different os versions (Android and iOS) - works on android 4.4+ and iOS 9, 10 - iOS 8.4 tested in emulator

Possibly resolved:

About

A cordova plugin which provides live ocr scanning capabilities for Android and iOS using Tesseract


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