ppu-paddle-ocr — React Native demo

An Expo app that runs the ppu-paddle-ocr/mobile OCR pipeline fully on-device (iOS / Android). Pick an image — the bundled receipt, one from the photo library, or a fresh camera capture — choose a model preset, and recognize the text. The result (text, confidence, timing) can be copied as JSON, and a live process log mirrors the recognition pipeline.

Requirements

ppu-paddle-ocr/mobile pulls in native modules (onnxruntime-react-native, @shopify/react-native-skia), so this needs a dev client or a prebuilt native project — Expo Go will not work.

• Node ≥ 18 and Bun (the repo is pinned with bun.lock)
• Xcode (iOS) and/or Android SDK + an emulator/device (Android)
• JDK 17 for the Android build
• Expo SDK 56 / React Native 0.85, New Architecture enabled (required by Reanimated 4 and Skia 2 — it cannot be turned off)

Run

cd ppu-paddle-ocr-mobile-react-native-demo
bun install

# Build & launch on a running emulator/simulator or device.
# Prebuild runs automatically; the scripts already set the autolinking flag.
bun run android      # or: bun run ios

The first OCR run downloads the PP-OCRv6 small models over the network and caches them for the session.

Native setup notes

These are already wired into the repo — documented here because they are easy to get wrong if you regenerate the native projects or bump versions.

• Community autolinking is forced on. onnxruntime-react-native is a legacy bridge module with no codegenConfig, and Expo's default autolinker only links New-Architecture modules — so it silently skips ONNX Runtime, leaving NativeModules.Onnxruntime null and crashing at startup with Cannot read property 'install' of null. The android / ios / prebuild scripts therefore set EXPO_USE_COMMUNITY_AUTOLINKING=1, which routes React Native modules through @react-native-community/cli (added as a devDependency) while Expo modules keep linking normally. react-native.config.js declares ONNX Runtime explicitly for that autolinker.
• react-native-worklets is a direct dependency. The community autolinker only links direct dependencies, and Reanimated 4 needs the worklets native library; Expo would have picked it up transitively.
• onnxruntime-react-native is patched. Its android/build.gradle calls VersionNumber.parse(...), an internal Gradle API removed in Gradle 9. The patch in patches/ swaps it for the package's own REACT_NATIVE_MINOR_VERSION check (applied automatically via bun's patchedDependencies).

How it works

import { PaddleOcrService } from "ppu-paddle-ocr/mobile";

const service = new PaddleOcrService();
await service.initialize();

const result = await service.recognize(imageBuffer, { flatten: true });
console.log(result.text, result.confidence);

await service.destroy();

• src/hooks/useOcr.ts — owns the service lifecycle and rebuilds it when the selected model preset changes; recognition runs on caller-supplied bytes.
• src/hooks/useImageSource.ts — resolves the bundled receipt, a library pick, or a camera capture (expo-image-picker) to an ArrayBuffer.
• src/ocr/presets.ts — the curated subset of the built-in model catalogue shown in the preset selector.
• src/logging/logStore.ts — mirrors console (including the library's verbose pipeline logs) into the on-screen Process log.
• App.tsx / src/components/* — source selector, model selector, preview, Run button, result card (with Copy JSON), and the log panel.

Notes

• CPU by default. Pass new PaddleOcrService({ session: { executionProviders: ["nnapi"] } }) on Android or ["coreml"] on iOS to opt into hardware acceleration.
• Smaller download. Pass a lighter preset, e.g. new PaddleOcrService({ model: V6_TINY_MODEL }), if app-start latency matters more than accuracy.