face_detection_tflite

A pure Dart/Flutter implementation of Google's MediaPipe face detection and facial landmark models using TensorFlow Lite. This package provides on-device face and landmark detection with minimal dependencies, just TensorFlow Lite and image.

Bounding Box Example:

Mesh (468-Point) Example:

Landmark Example:

Iris Example:

Features

• On-device face detection, runs fully offline
• 468 point mesh, face landmarks, iris landmarks and bounding boxes
• All coordinates are in absolute pixel coordinates
• Truly cross-platform: compatible with Android, iOS, macOS, Windows, and Linux
• The example app illustrates how to detect and render results on images
  • Includes demo for bounding boxes, the 468-point mesh, facial landmarks and iris landmarks.

Quick Start

import 'dart:io';
import 'dart:math'; // Required to work with Point<double> coordinates
import 'package:face_detection_tflite/face_detection_tflite.dart';

Future main() async {
  // Initialize & set model
  FaceDetector detector = FaceDetector();
  await detector.initialize(model: FaceDetectionModel.backCamera);

  // Detect faces
  final imageBytes = await File('path/to/image.jpg').readAsBytes();
  List<Face> faces = await detector.detectFaces(imageBytes);

  // Access results
  for (Face face in faces) {
    final landmarks = face.landmarks;
    final bbox = face.bbox;
    final mesh = face.mesh;
    final irises = face.irises;

    // FaceLandmarkType can be any of these:
    // leftEye, rightEye, noseTip, mouth, leftEyeTragion, or rightEyeTragion
    final leftEye = landmarks[FaceLandmarkType.leftEye];
    print('Left eye: (${leftEye?.x}, ${leftEye?.y})');
  }

  // Don't forget to clean-up when you're done!
  detector.dispose();
}

Bounding Boxes

The bbox property returns a BoundingBox object representing the face bounding box in absolute pixel coordinates. The BoundingBox provides convenient access to corner points, dimensions (width and height), and the center point.

Accessing Corners

import 'dart:math'; // Required for Point<double>

final BoundingBox bbox = face.bbox;

// Access individual corners by name (each is a Point<double> with x and y)
final Point<double> topLeft     = bbox.topLeft;       // Top-left corner
final Point<double> topRight    = bbox.topRight;      // Top-right corner
final Point<double> bottomRight = bbox.bottomRight;   // Bottom-right corner
final Point<double> bottomLeft  = bbox.bottomLeft;    // Bottom-left corner

// Access dimensions and center
final double width  = bbox.width;     // Width in pixels
final double height = bbox.height;    // Height in pixels
final Point<double> center = bbox.center;  // Center point

// Access all corners as a list (order: top-left, top-right, bottom-right, bottom-left)
final List<Point<double>> allCorners = bbox.corners;

// Access coordinates
print('Top-left: (${topLeft.x}, ${topLeft.y})');
print('Size: ${width} x ${height}');
print('Center: (${center.x}, ${center.y})');

Landmarks

The landmarks property returns a FaceLandmarks object with 6 key facial feature points in absolute pixel coordinates. These landmarks provide quick access to common facial features with convenient named properties.

Accessing Landmarks

import 'dart:math'; // Required for Point<double>

final FaceLandmarks landmarks = face.landmarks;

// Access individual landmarks using named properties
final Point<double>? leftEye  = landmarks.leftEye;
final Point<double>? rightEye = landmarks.rightEye;
final Point<double>? noseTip  = landmarks.noseTip;
final Point<double>? mouth    = landmarks.mouth;
final Point<double>? leftEyeTragion  = landmarks.leftEyeTragion;
final Point<double>? rightEyeTragion = landmarks.rightEyeTragion;

// Access coordinates
print('Left eye: (${leftEye?.x}, ${leftEye?.y})');
print('Nose tip: (${noseTip?.x}, ${noseTip?.y})');

// Backwards compatible: map-like access still works
final Point<double>? leftEyeAlt = landmarks[FaceLandmarkType.leftEye];

// Iterate through all landmarks
for (final point in landmarks.values) {
  print('Landmark: (${point.x}, ${point.y})');
}

Face Mesh

The mesh property returns a list of 468 facial landmark points that form a detailed 3D face mesh in absolute pixel coordinates. These points map to specific facial features and can be used for precise face tracking and rendering.

Accessing Points

import 'dart:math'; // Required for Point<double>

final List<Point<double>> mesh = face.mesh;

// Total number of points (always 468)
print('Mesh points: ${mesh.length}');

// Iterate through all points
for (int i = 0; i < mesh.length; i++) {
  final Point<double> point = mesh[i];
  print('Point $i: (${point.x}, ${point.y})');
}

// Access individual points (each is a Point<double> with x and y)
final Point<double> noseTip = mesh[1];     // Nose tip point
final Point<double> leftEye = mesh[33];    // Left eye point
final Point<double> rightEye = mesh[263];  // Right eye point

Irises

The irises property returns detailed iris tracking data for both eyes in absolute pixel coordinates. Each iris includes the center point and 5 contour points that outline the iris boundary. Only available in FaceDetectionMode.full.

Accessing Iris Data

import 'dart:math'; // Required for Point<double>

final IrisPair? irises = face.irises;

// Access left and right iris (each is an Iris object)
final Iris? leftIris = irises?.leftIris;
final Iris? rightIris = irises?.rightIris;

// Access iris center
final Point<double>? leftCenter = leftIris?.center;
print('Left iris center: (${leftCenter?.x}, ${leftCenter?.y})');

// Access iris contour points (4 points outlining the iris)
final List<Point<double>>? leftContour = leftIris?.contour;
for (int i = 0; i < (leftContour?.length ?? 0); i++) {
  final Point<double> point = leftContour![i];
  print('Left iris contour $i: (${point.x}, ${point.y})');
}

// Right iris
final Point<double>? rightCenter = rightIris?.center;
final List<Point<double>>? rightContour = rightIris?.contour;
print('Right iris center: (${rightCenter?.x}, ${rightCenter?.y})');

Face Detection Modes

This app supports three detection modes that determine which facial features are detected:

Mode	Features	Est. Time per Face*
Full (default)	Bounding boxes, landmarks, 468-point mesh, iris tracking	~80-120ms
Standard	Bounding boxes, landmarks, 468-point mesh	~60ms
Fast	Bounding boxes, landmarks	~30ms

*Est. times per faces are based on 640x480 resolution on modern hardware. Performance scales with image size and number of faces.

Code Examples

The Face Detection Mode can be set using the mode parameter when detectFaces is called. Defaults to FaceDetectionMode.full.

// Full mode (default): bounding boxes, 6 basic landmarks + mesh + iris
// note: full mode provides superior accuracy for left and right eye landmarks
// compared to fast/standard modes. use full mode when precise eye landmark
// detection is required for your application. trade-off: longer inference
await faceDetector.detectFaces(bytes, mode: FaceDetectionMode.full);

// Standard mode: bounding boxes, 6 basic landmarks + mesh. inference time 
// is faster than full mode, but slower than fast mode.
await faceDetector.detectFaces(bytes, mode: FaceDetectionMode.standard);

// Fast mode: bounding boxes + 6 basic landmarks only. fastest inference
// time of the three modes.
await faceDetector.detectFaces(bytes, mode: FaceDetectionMode.fast);

Try the sample code from the pub.dev example tab to easily compare modes and inferences timing.

Models

This package supports multiple detection models optimized for different use cases:

Model	Best For
backCamera (default)	Group shots, distant faces, rear camera
frontCamera	Selfies, close-up portraits, front camera
shortRange	Close-range faces (within ~2m)
full	Mid-range faces (within ~5m)
fullSparse	Mid-range faces with faster inference (~30% speedup)

Code Examples

The model can be set using the model parameter when initialize is called. Defaults to FaceDetectionModel.backCamera.

FaceDetector faceDetector = FaceDetector();

// backCamera (default): larger model for group shots or images with smaller faces
await faceDetector.initialize(model: FaceDetectionModel.backCamera);

// frontCamera: optimized for selfies and close-up portraits
await faceDetector.initialize(model: FaceDetectionModel.frontCamera);

// shortRange: best for short-range images (faces within ~2m)
await faceDetector.initialize(model: FaceDetectionModel.shortRange);

// full: best for mid-range images (faces within ~5m)
await faceDetector.initialize(model: FaceDetectionModel.full);

// fullSparse: same detection quality as full but runs up to 30% faster on CPU
// (slightly higher precision, slightly lower recall)
await faceDetector.initialize(model: FaceDetectionModel.fullSparse);

Example

The sample code from the pub.dev example tab includes a Flutter app that paints detections onto an image: bounding boxes, landmarks, mesh, and iris. The example code provides inference time, and demonstrates when to use FaceDetectionMode.standard or FaceDetectionMode.fast.

Inspiration

At the time of development, there was no open-source solution for cross-platform, on-device face and landmark detection. This package took inspiration and was ported from the original Python project patlevin/face-detection-tflite. Many thanks to the original author.