This is documentation for the next SDK version. For up-to-date documentation, see the latest version (SDK 51).

Expo FaceDetector

A library that uses Google Mobile Vision to detect faces on images.

Deprecated: This library will no longer be available from SDK 51. We recommend react-native-vision-camera if you require this functionality.

expo-face-detector lets you use the power of the Google's ML Kit framework to detect faces on images.

Known issues
Android

Face detector does not recognize faces that aren't aligned with the interface (top of the interface matches top of the head).

Installation

This module is not available in the Expo Go app because it has dependencies that break builds for iOS Simulators.

You can create a development build to work with this package.

Terminal

- npx expo install expo-face-detector

If you are installing this in an existing React Native app (bare workflow), start by installing expo in your project. Then, follow the additional instructions as mentioned by library's README under "Installation in bare React Native projects" section.

Usage

Settings

To configure detector's behavior modules pass a DetectionOptions object which is then interpreted by this module.

Example

You can use the following snippet to detect faces in a fast mode without detecting landmarks or whether a face is smiling.

Quick face detection

import * as React from 'react';
import { Camera } from 'expo-camera';
import * as FaceDetector from 'expo-face-detector';

const App = () => (
  <Camera
    // other props
    onFacesDetected={handleFacesDetected}
    faceDetectorSettings={{
      mode: FaceDetector.FaceDetectorMode.fast,
      detectLandmarks: FaceDetector.FaceDetectorLandmarks.none,
      runClassifications: FaceDetector.FaceDetectorClassifications.none,
      minDetectionInterval: 100,
      tracking: true,
    }}
  />
);

const handleFacesDetected = ({ faces }) => {
  console.log(faces);
};

export default App;

API

import * as FaceDetector from 'expo-face-detector';

Methods

Deprecated If you require this functionality, we recommend using react-native-vision-camera

Android

iOS

`FaceDetector.detectFacesAsync(uri, options)`

Name	Type	Description
uri	`string`	`file://` URI to the image.
options (optional)	`DetectionOptions`	A map of detection options. Default: `{}`

Detect faces on a picture.

Returns:

Promise<DetectionResult>

Returns a Promise which fulfils with DetectionResult object.

Types

Android

iOS

`DetectionOptions`

In order to configure detector's behavior modules pass a settings object which is then interpreted by this module.

Name	Type	Description
detectLandmarks (optional)	`FaceDetectorLandmarks`	Whether to detect and return landmarks positions on the face (ears, eyes, mouth, cheeks, nose). Use `FaceDetector.FaceDetectorLandmarks.{all, none}`.
minDetectionInterval (optional)	`number`	Minimal interval in milliseconds between two face detection events being submitted to JS. Use, when you expect lots of faces for long time and are afraid of JS Bridge being overloaded. Default: `0`
mode (optional)	`FaceDetectorMode`	Whether to detect faces in fast or accurate mode. Use `FaceDetector.FaceDetectorMode.{fast, accurate}`.
runClassifications (optional)	`FaceDetectorClassifications`	Whether to run additional classifications on detected faces (smiling probability, open eye probabilities). Use `FaceDetector.FaceDetectorClassifications.{all, none}`.
tracking (optional)	`boolean`	Flag to enable tracking of faces between frames. If true, each face will be returned with `faceID` attribute which should be consistent across frames. Default: `false`

Android

iOS

`DetectionResult`

Name	Type	Description
faces	`FaceFeature[]`	Array of faces objects.
image	`Image`	-

Android

iOS

`FaceFeature`

Name	Type	Description
bottomMouthPosition (optional)	`Point`	Position of the bottom edge of the mouth in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
bounds	`FaceFeatureBounds`	An object containing face bounds.
faceID (optional)	`number`	A face identifier (used for tracking, if the same face appears on consecutive frames it will have the same `faceID`).
leftCheekPosition (optional)	`Point`	Position of the left cheek in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
leftEarPosition (optional)	`Point`	Position of the left ear in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
leftEyeOpenProbability (optional)	`number`	Probability that the left eye is open. Returned only if detection classifications property is set to `FaceDetectorClassifications.all`.
leftEyePosition (optional)	`Point`	Position of the left eye in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
leftMouthPosition (optional)	`Point`	Position of the left edge of the mouth in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
mouthPosition (optional)	`Point`	Position of the center of the mouth in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
noseBasePosition (optional)	`Point`	Position of the nose base in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
rightCheekPosition (optional)	`Point`	Position of the right cheek in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
rightEarPosition (optional)	`Point`	Position of the right ear in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
rightEyeOpenProbability (optional)	`number`	Probability that the right eye is open. Returned only if detection classifications property is set to `FaceDetectorClassifications.all`.
rightEyePosition (optional)	`Point`	Position of the right eye in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
rightMouthPosition (optional)	`Point`	Position of the right edge of the mouth in image coordinates. Returned only if detection classifications property is set to `FaceDetectorLandmarks.all`.
rollAngle (optional)	`number`	Roll angle of the face (bank).
smilingProbability (optional)	`number`	Probability that the face is smiling. Returned only if detection classifications property is set to `FaceDetectorClassifications.all`.
yawAngle (optional)	`number`	Yaw angle of the face (heading, turning head left or right).

Android

iOS

`FaceFeatureBounds`

Name	Type	Description
origin	`Point`	Position of the top left corner of a square containing the face in image coordinates,
size	`{ height: number, width: number }`	Size of the square containing the face in image coordinates,

Android

iOS

`Image`

Name	Type	Description
height	`number`	Height of the image in pixels.
orientation	`number`	Orientation of the image (value conforms to the EXIF orientation tag standard).
uri	`string`	URI of the image.
width	`number`	Width of the image in pixels.

Android

iOS

`Point`

Name	Type	Description
x	`number`	-
y	`number`	-

iOS

Expo FaceDetector

Known issues
Android

Installation

Usage

Settings

Example

API

Methods

`FaceDetector.detectFacesAsync(uri, options)`

Types

`DetectionOptions`

`DetectionResult`

`FaceFeature`

`FaceFeatureBounds`

`Image`

`Point`

Enums

`FaceDetectorClassifications`

`none`

`all`

`FaceDetectorLandmarks`

`none`

`all`

`FaceDetectorMode`

`fast`

`accurate`