rn-ocr-lib

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.

Showcase

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

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