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@zhanziyang/expo-text-extractor
@zhanziyang/expo-text-extractor/build/index.js

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Readme

Expo Text Extractor

Fork Notice: This is a fork of pchalupa/expo-text-extractor with added multi-language support for Chinese, Japanese, Korean, and Devanagari scripts.

Expo Text Extractor is a library that enables text recognition (OCR) using Google ML Kit on Android and Apple Vision on iOS.

Platform Compatibility

Android Device	Android Emulator	iOS Device	iOS Simulator	Web
✅	✅	✅	✅	❌

Supported Languages

The library supports multiple scripts and languages:

Script	Languages	Android	iOS
Latin	English, Spanish, French, German, Italian, etc.	✅	✅
Chinese	Simplified Chinese, Traditional Chinese	✅	✅
Japanese	Japanese (Hiragana, Katakana, Kanji)	✅	✅
Korean	Korean (Hangul)	✅	✅
Devanagari	Hindi, Sanskrit, Marathi, Nepali, etc.	✅	✅

Demo

demo

Installation

To get started, install the library:

npx expo install @zhanziyang/expo-text-extractor

Or with npm/yarn:

npm install @zhanziyang/expo-text-extractor
# or
yarn add @zhanziyang/expo-text-extractor

Ensure your project is running Expo SDK 52+.

API Documentation

Check the example app for more details.

`isSupported`

A boolean value indicating whether the current device supports text extraction.

import { isSupported } from '@zhanziyang/expo-text-extractor';

if (isSupported) {
  console.log('Text extraction is supported on this device.');
}

`extractTextFromImage(uri, options?)`

Extracts text from an image and returns the recognized text as an array.

import { extractTextFromImage, TextRecognitionScript } from '@zhanziyang/expo-text-extractor';

// Basic usage (Latin script by default)
const texts = await extractTextFromImage('file:///path/to/image.jpg');

// With a specific script (Android)
const chineseTexts = await extractTextFromImage('file:///path/to/image.jpg', {
  script: TextRecognitionScript.CHINESE,
});

// With specific languages (iOS)
const japaneseTexts = await extractTextFromImage('file:///path/to/image.jpg', {
  languages: ['ja-JP', 'en-US'],
});

Parameters

Parameter	Type	Description
`uri`	`string`	The URI of the image to extract text from.
`options`	`RecognitionOptions`	Optional. Recognition options (see below).

Recognition Options

Property	Type	Platform	Default	Description
`script`	`TextRecognitionScript`	Android	`LATIN`	The script type to use for recognition.
`languages`	`string[]`	iOS	-	Array of BCP-47 language codes (e.g., `'en-US'`, `'zh-Hans'`, `'ja-JP'`).
`automaticallyDetectsLanguage`	`boolean`	iOS 16+	`false`	Automatically detect language without specifying `languages`.
`usesLanguageCorrection`	`boolean`	iOS	`true`	Apply language correction to improve recognition accuracy.
`customWords`	`string[]`	iOS	-	Custom words (proper nouns, technical terms) to help with recognition.
`minimumTextHeight`	`number`	iOS	~0.03	Minimum text height as fraction of image height (0-1). Lower values detect smaller text.
`recognitionLevel`	`RecognitionLevel`	iOS	`ACCURATE`	Recognition level: `ACCURATE` (slower, better) or `FAST` (faster, less accurate).

TextRecognitionScript Enum (Android)

Value	Description
`LATIN`	Latin script - English, Spanish, French, German, Italian, etc.
`CHINESE`	Chinese script - Simplified and Traditional Chinese
`DEVANAGARI`	Devanagari script - Hindi, Sanskrit, Marathi, Nepali, etc.
`JAPANESE`	Japanese script - Hiragana, Katakana, Kanji
`KOREAN`	Korean script - Hangul

RecognitionLevel Enum (iOS)

Value	Description
`ACCURATE`	Slower but more accurate recognition (default).
`FAST`	Faster but less accurate recognition.

`getSupportedLanguages()`

Returns the list of supported languages on the current platform.

import { getSupportedLanguages } from '@zhanziyang/expo-text-extractor';

const languages = await getSupportedLanguages();
console.log(languages);
// iOS: ['en-US', 'fr-FR', 'de-DE', 'zh-Hans', 'zh-Hant', 'ja-JP', 'ko-KR', ...]
// Android: ['latin', 'chinese', 'devanagari', 'japanese', 'korean']

Platform-Specific Notes

Android (ML Kit)

Each script requires a separate ML Kit model that is downloaded on-demand by Google Play Services.
The first recognition request for a new script may be slower as the model downloads.
All script models are included by default. If you want to reduce app size, you can create a custom build configuration.

iOS (Vision)

The Vision framework automatically detects the script in most cases.
Use the languages option for best results when you know the expected language(s).
Call getSupportedLanguages() to get the full list of available languages for the device.
Language support may vary by iOS version. Korean support was added in iOS 16.

Examples

Recognizing Chinese Text

import { extractTextFromImage, TextRecognitionScript } from '@zhanziyang/expo-text-extractor';

const recognizeChineseText = async (imageUri: string) => {
  const texts = await extractTextFromImage(imageUri, {
    script: TextRecognitionScript.CHINESE,
    // On iOS, you can also specify:
    // languages: ['zh-Hans', 'zh-Hant'],
  });
  
  return texts.join('\n');
};

Recognizing Japanese Text

import { extractTextFromImage, TextRecognitionScript } from '@zhanziyang/expo-text-extractor';

const recognizeJapaneseText = async (imageUri: string) => {
  const texts = await extractTextFromImage(imageUri, {
    script: TextRecognitionScript.JAPANESE,
    // On iOS:
    // languages: ['ja-JP'],
  });
  
  return texts.join('\n');
};

Recognizing Korean Text

import { extractTextFromImage, TextRecognitionScript } from '@zhanziyang/expo-text-extractor';

const recognizeKoreanText = async (imageUri: string) => {
  const texts = await extractTextFromImage(imageUri, {
    script: TextRecognitionScript.KOREAN,
    // On iOS:
    // languages: ['ko-KR'],
  });
  
  return texts.join('\n');
};

Multi-language Recognition (iOS)

On iOS, you can specify multiple preferred languages:

import { extractTextFromImage } from '@zhanziyang/expo-text-extractor';

const recognizeMultiLanguage = async (imageUri: string) => {
  const texts = await extractTextFromImage(imageUri, {
    // Recognize Japanese with English as fallback
    languages: ['ja-JP', 'en-US'],
  });
  
  return texts.join('\n');
};

Advanced iOS Options

Use all available iOS Vision options for fine-tuned recognition:

import { extractTextFromImage, RecognitionLevel } from '@zhanziyang/expo-text-extractor';

const advancedRecognition = async (imageUri: string) => {
  const texts = await extractTextFromImage(imageUri, {
    // Specify preferred languages
    languages: ['en-US'],
    
    // Or let iOS auto-detect (iOS 16+)
    automaticallyDetectsLanguage: true,
    
    // Enable language correction for better accuracy
    usesLanguageCorrection: true,
    
    // Add custom words for better recognition of proper nouns
    customWords: ['iPhone', 'MacBook', 'AirPods', 'WWDC'],
    
    // Ignore very small text (5% of image height)
    minimumTextHeight: 0.05,
    
    // Use accurate mode (default) or fast mode
    recognitionLevel: RecognitionLevel.ACCURATE,
  });
  
  return texts.join('\n');
};

Fast Recognition Mode (iOS)

For real-time processing or when speed is critical:

import { extractTextFromImage, RecognitionLevel } from '@zhanziyang/expo-text-extractor';

const fastRecognition = async (imageUri: string) => {
  const texts = await extractTextFromImage(imageUri, {
    recognitionLevel: RecognitionLevel.FAST,
    usesLanguageCorrection: false, // Disable for extra speed
  });
  
  return texts.join('\n');
};

Credits

License

MIT