dni_peru_ocr 0.11.2

Peruvian DNI OCR helpers — ML Kit text recognition denoise, MRZ parsing, address extraction, and surname normalization for the Peruvian Documento Nacional de Identidad.

dni_peru_ocr

Peruvian DNI OCR helpers for Flutter — denoise the Google ML Kit Latin TextRecognizer output against the Documento Nacional de Identidad and recover clean, structured fields with temporal consensus across frames.

Why

A single ML Kit frame on a Peruvian DNI is noisy: Ñ is encoded as NXX on the MRZ line, address labels (DIRECCIÓN) collide with QR artifacts, civic-box content (CONSTANCIA DE SUFRAGIO) drowns the real address, and document tilt skews block geometry. This package solves these problems with a layered, side-by-side strategy pipeline plus a temporal accumulator — no manual cleanup required at the consumer.

Features

• MRZ parsing — ICAO 9303 TD1 with checksum validation via mrz_parser, plus Peruvian-specific Ñ → NXX recovery.
• Strategy decomposition — three independent extractors (MrzFieldStrategy, TextOcrFieldStrategy, AddressFieldStrategy) combined by a thin coordinator. Each strategy is stateless and individually testable.
• Temporal consensus — OcrConsensusAccumulator votes across frames and emits a deterministic winner even under noisy OCR (address vote consolidation tolerates micro-variants; name votes consolidate by strict prefix containment).
• Ubigeo extraction — populates department, province, and district from the back-side administrative line (ANCASH/SANTA/ CHIMBOTE, /CALLAO/VENTANILLA, LIMA/LIMA/VILLA MARIA DEL TRIUNFO).
• Pluggable observability — inject your own OcrLogger (Sentry, Crashlytics, Datadog, custom) at the extractor constructor.
• Production-ready capture widget — DniCameraMask ships with auto-capture, manual fallback, tilt detection, side-toggle seeding, and dispose-safe lifecycle. Pure-Dart DniCameraController is exposed for headless use.

Installation

dependencies:
  dni_peru_ocr: ^0.7.1

Note: as of v0.11.1, dio is a direct runtime dependency of this package (required for pub.dev compliance). You don't need to add it to your own pubspec.yaml.

flutter pub get

Install from source

dependencies:
  dni_peru_ocr:
    git:
      url: https://github.com/DarkCodex29/dni_peru_ocr.git
      ref: v0.7.1

Example

A runnable example app is available under example/. It demonstrates the complete DNI capture flow — front scan, back scan with frontSideFields seeding, and result display with per-field confidence indicators — on a real Android or iOS device. See example/README.md for setup instructions and a walkthrough of the recommended integration pattern.

Quick start — headless extraction

import 'package:dni_peru_ocr/dni_peru_ocr.dart';

// Static entry point — no logger, default strategies.
final fields = OcrFieldExtractor.extract(recognizedText);

print(fields.firstName);      // JUAN CARLOS
print(fields.lastName);       // MUÑOZ
print(fields.secondLastName); // PEREZ
print(fields.address);        // AV. SANTA ROSA 1080 MARIATEGUI
print(fields.department);     // LIMA
print(fields.province);       // LIMA
print(fields.district);       // VILLA MARIA DEL TRIUNFO

To route OCR/MRZ mismatch breadcrumbs through your observability stack, use the instance API:

const extractor = OcrFieldExtractor(logger: SentryOcrLogger());
final fields = extractor.extractWith(recognizedText);

Quick start — capture widget

DniCameraMask is a Flutter widget that owns the full capture flow. The host provides a camera plugin CameraController and listens for the final capture via the onValidCapture callback.

import 'package:dni_peru_ocr/dni_peru_ocr.dart';

DniCameraMask(
  controller: cameraController,
  isBackSide: false,
  onValidCapture: (file, consensus) {
    // consensus is null on the front side, populated on the back.
    if (consensus != null) {
      print(consensus.firstName.value);
      print(consensus.address.value);
    }
  },
  // Required for two-sided scans: persist front OCR into your state
  // holder and feed it back as the back-side seed.
  onFrontSideOcrUpdated: (fields) => myStateHolder.frontSideOcr = fields,
)

// ...later, when mounting the back-side step:
DniCameraMask(
  controller: cameraController,
  isBackSide: true,
  frontSideFields: myStateHolder.frontSideOcr, // ← seed
  onValidCapture: (file, consensus) { /* ... */ },
)

Why the state-holder dance? Flutter destroys widget State when the host swaps from front to back via a switch over an enum step, so the front side's accumulated OCR is lost unless the host persists it. The frontSideFields parameter restores it.

DNI Lookup

Beyond OCR, dni_peru_ocr ships a flexible lookup contract so you can fetch normalized DNI data from any backend. The lookup feature is fully optional — OCR-only consumers compile and run identically to v0.7.x.

Recommended composition — caching + service

Implement DniCache for your storage layer (Hive, Isar, SharedPreferences, or just in-memory), then compose with a concrete service:

import 'package:dio/dio.dart';
import 'package:dni_peru_ocr/dni_peru_ocr.dart';

// Minimal in-memory cache — replace with Hive / Isar in production.
class InMemoryDniCache implements DniCache {
  final Map<String, DniData> _store = {};

  @override
  Future<DniData?> get(String dni) async => _store[dni];

  @override
  Future<void> set(String dni, DniData data) async => _store[dni] = data;

  @override
  Future<void> evict(String dni) async => _store.remove(dni);
}

final lookup = CachingDniLookupService(
  delegate: ReniecSunatLookupService(
    httpClient: DioDniHttpClient(Dio()),
    baseUrl: 'https://your-reniec-sunat-backend.example.com',
  ),
  cache: InMemoryDniCache(),
  ttl: const Duration(minutes: 5),
);

final result = await lookup.lookup('43005787');
switch (result) {
  case DniLookupSuccess(:final data):
    print(data.nombreCompleto);
  case DniLookupNotFound():
    print('DNI not found');
  case _:
    print('Lookup failed');
}

Multi-backend fallback

For setups where you want to try a primary service and fall back to a secondary, use FallbackDniLookupService. It stops the chain on DniLookupInvalidToken by default so you do not hammer a service with bad credentials:

final lookup = FallbackDniLookupService(
  services: [primaryService, secondaryService],
);

final result = await lookup.lookup('43005787');

The retry predicate is configurable — pass retryOn to override which result types allow the chain to continue.

Field Selection

If your app only needs a subset of fields, configure the scanner with a DniFields to reduce CPU usage.

final scanner = DniScanner(
  controller: cameraController,
  fields: DniFields.kyc(),
  onScanComplete: (result) { ... },
);

Built-in presets:

• DniFields.minimal() — 4 fields (dni, firstName, lastName, secondLastName)
• DniFields.kyc() — 7 fields for KYC flows
• DniFields.full() — all 19 fields (default behavior when omitted)

Or define a custom set: DniFields.required({DniField.documentNumber, DniField.firstName, DniField.address}).

Public API

Type	Purpose
OcrFieldExtractor	Static + instance extraction coordinator.
OcrExtractedFields	Mutable field bag (document number, names, address, ubigeo).
OcrConsensusAccumulator	Per-field vote accumulator across frames.
OcrConsensusResult	Immutable snapshot of the accumulator.
MrzFieldStrategy	MRZ-only extractor (checksum-valid).
TextOcrFieldStrategy	Label-anchored text extractor.
AddressFieldStrategy	Address + ubigeo extractor with multi-line stitching.
OcrFieldStrategy	Interface for custom strategies.
OcrFieldNormalizer	Pure normalization helpers (Ñ recovery, document, date).
AddressNoiseFilter	Peruvian address vocabulary + noise-token filter.
StringSimilarity	Levenshtein utilities.
OcrLogger / NoOpOcrLogger	Observability hook (default no-op).
DniCameraMask	Production capture widget.
DniCameraController	Pure-Dart capture state machine.
DniCaptureOrchestrator	Auto-capture countdown logic.
DniCaptureState (sealed)	Capture state hierarchy.
DocumentValidationResult	Geometric + OCR validation gate.
ValidationGate (enum)	Exhaustive failing-gate cases.
ValidationGateColors	Presentation-side gate → color mapping.
KycTheme / KycThemeProvider	Inject visual identity into the capture widget.
UserVerificationData	Pre-scan user context for OCR-vs-user matching.

Logging adapter example

import 'package:dni_peru_ocr/dni_peru_ocr.dart';
import 'package:sentry_flutter/sentry_flutter.dart';

class SentryOcrLogger implements OcrLogger {
  const SentryOcrLogger();

  @override
  void breadcrumb(String category, String message, {Map<String, Object?>? data}) {
    Sentry.addBreadcrumb(
      Breadcrumb(
        category: category,
        message: message,
        data: data,
        level: SentryLevel.info,
      ),
    );
  }
}

Architecture

lib/src/
├── domain/           — entities + interfaces, pure Dart
│   ├── entities/     (UserVerificationData, ValidationGate)
│   └── interfaces/   (OcrLogger)
├── data/             — extraction strategies + accumulator
│   ├── strategies/   (Mrz / TextOcr / Address)
│   ├── ocr_consensus.dart
│   ├── ocr_field_extractor.dart
│   ├── ocr_field_normalizer.dart
│   ├── address_noise_filter.dart
│   └── string_similarity.dart
├── infrastructure/   — ML Kit / camera lifecycle utilities
└── presentation/     — Flutter widgets + controllers
    ├── controllers/  (DniCameraController)
    ├── orchestrators/(DniCaptureOrchestrator + sealed state)
    ├── widgets/      (DniCameraMask + sub-widgets)
    └── theme/        (KycTheme + provider)

Follows Clean Architecture (domain has no Flutter import). Each layer depends only on its inner neighbours. Strategies follow the Strategy pattern; consensus follows the Accumulator pattern.

Roadmap

v0.7.0 (current)

• Ubigeo fields (department, province, district).
• Name vote consolidation by strict prefix containment.
• Address locked flag requires ≥ 2 corroborating frames.
• tiltCalculator becomes a constructor parameter (last global mutable static removed from the public surface).
• Deprecated aliases removed: OcrConsensusBuilder typedef, OcrFieldExtractor.extractStatic, evaluate(theme:).
• Property-based shuffle tests + WidgetTester E2E state-lifecycle tests.

v0.6.x — bug-fix cycle on top of v0.6.0

Nine patch releases addressing real-world DNI OCR cases. See CHANGELOG.md.

v0.6.0

• Clean Architecture refactor (5 PRs).
• Strategy + Accumulator decomposition.
• DniCameraMask God Object split into widget + controller + orchestrator.
• GitHub Actions CI on every PR / push to main.

Planned — sibling library

face_validator_peru: extract face validation + selfie capture into a separate package mirroring this one's structure. Face logic currently lives in the consumer app.

Testing

flutter test                # 529 tests
flutter analyze             # 0 issues on a clean checkout

CI runs both on every push and PR (see .github/workflows/ci.yaml).

License

MIT — see LICENSE.