rn-ocr-lib
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0.2.4 • Public • Published

rn-ocr-lib

React native library to perform OCR on images. This library uses Tesseract library for image processing in android and vision library for iOS.

Npm package version Npm package monthly downloads License: MIT

React Native Android iOS

Showcase

Demo

Installation

npm install rn-ocr-lib
# or
yarn add rn-ocr-lib

Setup

Android

Create folder app/src/main/assets/tessdata. Inside tessdata place ${lang}.traineddata. You can get the train data files from here.

iOS

Vision library is present in iOS from version 13 or above. So update ios/Podfile.

platform :ios, '13.0'

Usage

Kindly refer the example project for usage for Android and iOS.

API Reference

Methods

import { getText, useOCREventListener } from 'rn-ocr-lib';

getText

Call this method to initiate image processing

getText(data: string, dataInputType: DataInputType, options?: Partial<OCROptions>): void;

useOCREventListener

Call this hook to setup listener to listen to progress, result and error.

useOCREventListener(
  (event: OCREventType, ocrEventResponse: OCREventResponse) => {
    switch (event) {
      case OCREvent.FINISHED:
        return;
      case OCREvent.PROGRESS:
        return;
      case OCREvent.ERROR:
        return;
      default:
        return;
    }
  }
);

Parameters

dataInputType

Input type Value Description
file FILE Path to image file
base64 BASE64 Base64 string


options

Option Type iOS Android Default Description
ocrEngineMode OCREngineMode Yes Yes FAST Type of mode between fast or accurate recognization
pageSegMode PageSegMode No Yes PSM_OSD_ONLY Page seg mode of tesseract
lang string[] Yes Yes ["eng"] Languages for which recognization is needed


ocrEngineMode

Engine Mode Value Description
FAST 0 Fast mode where recognization will be faster but mismatch of words is possible
ACCURATE 1 Accurate mode where time to process is more but more accurate text will be obtained
FAST_ACCURATE 2 Relavant for android tesseract where train data is provided for accurate and fast results but traindata file may be bigger compared to previous modes


pageSegMode (Android)

By default Tesseract expects a page of text when it segments an image. If you’re just seeking to OCR a small region, try a different segmentation mode.

Segmentation Mode Value Description
PSM_OSD_ONLY 0 Orientation and script detection (OSD) only.
PSM_AUTO_OSD 1 Automatic page segmentation with OSD.
PSM_AUTO_ONLY 2 Automatic page segmentation, but no OSD, or OCR.
PSM_AUTO 3 Fully automatic page segmentation, but no OSD. (Default)
PSM_SINGLE_COLUMN 4 Assume a single column of text of variable sizes.
PSM_SINGLE_BLOCK_VERT_TEXT 5 Assume a single uniform block of vertically aligned text.
PSM_SINGLE_BLOCK 6 Assume a single uniform block of text.
PSM_SINGLE_LINE 7 Treat the image as a single text line.
PSM_SINGLE_WORD 8 Treat the image as a single word.
PSM_CIRCLE_WORD 9 Treat the image as a single word in a circle.
PSM_SINGLE_CHAR 10 Treat the image as a single character.
PSM_SPARSE_TEXT 11 Sparse text. Find as much text as possible in no particular order.
PSM_SPARSE_TEXT_OSD 12 Sparse text with OSD.
PSM_RAW_LINE 13 Raw line. Treat the image as a single text line, bypassing hacks that are Tesseract-specific.


event

Event type Value Description
FINISHED finished Event when OCR completes
PROGRESS progress Progress event when OCR is processing
ERROR error Error event OCR fails and some error is being thrown


ocrEventResponse

Key Type Description
text string Result text
progress number Progress percent
error string Error message

Language Support

Android

Here is the list of supported languages for android.

iOS

Vision library currently has limited language support. It supports the following languages.

Language Code
English eng
France fra
Italian ita
German deu
Spanish spa
Portuguese por
Chinese Simplified chi_sim
Chinese Traditional chi_tra

Contributing

See the contributing guide to learn how to contribute to the repository and the development workflow.

License

MIT


Made with create-react-native-library

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Install

npm i rn-ocr-lib

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Version

0.2.4

License

MIT

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