expo-camera

What is expo-camera?

The expo-camera package is a part of the Expo ecosystem and provides a comprehensive API for accessing and using the device's camera in React Native applications. It allows developers to capture photos, record videos, and access various camera settings and features.

What are expo-camera's main functionalities?

Capture Photos

This feature allows you to capture photos using the device's camera. The code sample demonstrates how to set up the Camera component and take a picture when a button is pressed.

```javascript
import React, { useRef } from 'react';
import { View, Button } from 'react-native';
import { Camera } from 'expo-camera';

export default function App() {
  const cameraRef = useRef(null);

  const takePicture = async () => {
    if (cameraRef.current) {
      const photo = await cameraRef.current.takePictureAsync();
      console.log(photo);
    }
  };

  return (
    <View style={{ flex: 1 }}>
      <Camera style={{ flex: 1 }} ref={cameraRef} />
      <Button title="Take Picture" onPress={takePicture} />
    </View>
  );
}
```

Record Videos

This feature allows you to record videos using the device's camera. The code sample demonstrates how to set up the Camera component and start/stop video recording when a button is pressed.

```javascript
import React, { useRef, useState } from 'react';
import { View, Button } from 'react-native';
import { Camera } from 'expo-camera';

export default function App() {
  const cameraRef = useRef(null);
  const [isRecording, setIsRecording] = useState(false);

  const recordVideo = async () => {
    if (cameraRef.current) {
      if (isRecording) {
        cameraRef.current.stopRecording();
      } else {
        setIsRecording(true);
        const video = await cameraRef.current.recordAsync();
        console.log(video);
        setIsRecording(false);
      }
    }
  };

  return (
    <View style={{ flex: 1 }}>
      <Camera style={{ flex: 1 }} ref={cameraRef} />
      <Button title={isRecording ? "Stop Recording" : "Record Video"} onPress={recordVideo} />
    </View>
  );
}
```

Access Camera Settings

This feature allows you to access and modify camera settings such as switching between the front and back cameras. The code sample demonstrates how to request camera permissions and toggle the camera type.

```javascript
import React, { useState, useEffect } from 'react';
import { View, Text } from 'react-native';
import { Camera } from 'expo-camera';

export default function App() {
  const [hasPermission, setHasPermission] = useState(null);
  const [cameraType, setCameraType] = useState(Camera.Constants.Type.back);

  useEffect(() => {
    (async () => {
      const { status } = await Camera.requestPermissionsAsync();
      setHasPermission(status === 'granted');
    })();
  }, []);

  if (hasPermission === null) {
    return <View />;
  }
  if (hasPermission === false) {
    return <Text>No access to camera</Text>;
  }

  return (
    <View style={{ flex: 1 }}>
      <Camera style={{ flex: 1 }} type={cameraType} />
      <Button
        title="Flip Camera"
        onPress={() => {
          setCameraType(
            cameraType === Camera.Constants.Type.back
              ? Camera.Constants.Type.front
              : Camera.Constants.Type.back
          );
        }}
      />
    </View>
  );
}
```

Other packages similar to expo-camera

react-native-camera

The react-native-camera package is a popular alternative to expo-camera. It provides similar functionalities such as capturing photos, recording videos, and accessing camera settings. However, it requires linking and additional setup compared to the more streamlined experience of expo-camera within the Expo ecosystem.

react-native-vision-camera

The react-native-vision-camera package offers advanced camera functionalities, including frame processing and integration with machine learning models. It is more feature-rich compared to expo-camera but also requires more complex setup and configuration.

README

expo-camera

Installation

iOS (Cocoapods)

If you're using Cocoapods, add the dependency to your Podfile:

pod 'EXCamera'

and run pod install.

iOS (no Cocoapods)

1. In XCode, in the project navigator, right click Libraries ➜ Add Files to [your project's name]
2. Go to node_modules ➜ expo-camera and add EXCamera.xcodeproj
3. In XCode, in the project navigator, select your project. Add libEXCamera.a to your project's Build Phases ➜ Link Binary With Libraries
4. Run your project (Cmd+R).

Android

1. Append the following lines to android/settings.gradle:

   include ':expo-camera'
   project(':expo-camera').projectDir = new File(rootProject.projectDir, '../node_modules/expo-camera/android')
   

   and if not already included

   include ':expo-permissions-interface'
   project(':expo-permissions-interface').projectDir = new File(rootProject.projectDir, '../node_modules/expo-permissions-interface/android')
   

2. Insert the following lines inside the dependencies block in android/app/build.gradle:

   compile project(':expo-camera')
   

   and if not already included

   compile project(':expo-permissions-interface')
   

Introduction

A React component that renders a preview for the device's either front or back camera. Camera's parameters like zoom, auto focus, white balance and flash mode are adjustable. With use of Camera one can also take photos and record videos that are saved to the app's cache. Morever, the component is also capable of detecting faces and bar codes appearing on the preview.

Note: Only one Camera preview is supported by this library right now. When using navigation, the best practice is to unmount previously rendered Camera component so next screens can use camera without issues.

Note: Android devices can use one of two available Camera apis underneath. This was previously chosen automatically, based on the device's Android system version and camera hardware capabilities. As we experienced some issues with Android's Camera2 API, we decided to choose the older API as a default. However, using the newer one is still possible through setting useCamera2Api prop to true. The change we made should be barely visible - the only thing that is not supported using the old Android's API is setting focus depth.

Requires Permissions.CAMERA. Video recording requires Permissions.AUDIO_RECORDING. (See expo-permissions package).

Basic Example

import React from 'react';
import { Text, View, TouchableOpacity } from 'react-native';
import { Permissions } from 'expo-permissions';
import { Camera } from 'expo-camera';

export default class CameraExample extends React.Component {
  state = {
    hasCameraPermission: null,
    type: Camera.Constants.Type.back,
  };

  async componentWillMount() {
    const { status } = await Permissions.askAsync(Permissions.CAMERA);
    this.setState({ hasCameraPermission: status === 'granted' });
  }

  render() {
    const { hasCameraPermission } = this.state;
    if (hasCameraPermission === null) {
      return <View />;
    } else if (hasCameraPermission === false) {
      return <Text>No access to camera</Text>;
    } else {
      return (
        <View style={{ flex: 1 }}>
          <Camera style={{ flex: 1 }} type={this.state.type}>
            <View
              style={{
                flex: 1,
                backgroundColor: 'transparent',
                flexDirection: 'row',
              }}>
              <TouchableOpacity
                style={{
                  flex: 0.1,
                  alignSelf: 'flex-end',
                  alignItems: 'center',
                }}
                onPress={() => {
                  this.setState({
                    type:
                      this.state.type === Camera.Constants.Type.back
                        ? Camera.Constants.Type.front
                        : Camera.Constants.Type.back,
                  });
                }}>
                <Text style={{ fontSize: 18, marginBottom: 10, color: 'white' }}> Flip </Text>
              </TouchableOpacity>
            </View>
          </Camera>
        </View>
      );
    }
  }
}

props

• type

Camera facing. Use one of Camera.Constants.Type. When Type.front, use the front-facing camera. When Type.back, use the back-facing camera. Default: Type.back.

• flashMode

Camera flash mode. Use one of Camera.Constants.FlashMode. When on, the flash on your device will turn on when taking a picture, when off, it won't. Setting to auto will fire flash if required, torch turns on flash during the preview. Default: off.

• autoFocus

State of camera auto focus. Use one of Camera.Constants.AutoFocus. When on, auto focus will be enabled, when off, it wont't and focus will lock as it was in the moment of change but it can be adjusted on some devices via focusDepth prop.

• zoom (float)

A value between 0 and 1 being a percentage of device's max zoom. 0 - not zoomed, 1 - maximum zoom. Default: 0.

• whiteBalance

Camera white balance. Use one of Camera.Constants.WhiteBalance: auto, sunny, cloudy, shadow, fluorescent, incandescent. If a device does not support any of these values previous one is used.

• focusDepth (float)

Distance to plane of sharpest focus. A value between 0 and 1: 0 - infinity focus, 1 - focus as close as possible. Default: 0. For Android this is available only for some devices and when useCamera2Api is set to true.

• ratio (string)

Android only. A string representing aspect ratio of the preview, eg. 4:3, 16:9, 1:1. To check if a ratio is supported by the device use getSupportedRatiosAsync. Default: 4:3.

• onCameraReady (function)

Callback invoked when camera preview has been set.

• onFacesDetected (function)

Callback invoked with results of face detection on the preview. It will receive an object containing:

• faces (array) - array of faces objects:
  • faceID (number) -- a face identifier (used for tracking, if the same face appears on consecutive frames it will have the same faceID).
  • bounds (object) -- an object containing:
    • origin ({ x: number, y: number }) -- position of the top left corner of a square containing the face in view coordinates,
    • size ({ width: number, height: number }) -- size of the square containing the face in view coordinates,
  • rollAngle (number) -- roll angle of the face (bank),
  • yawAngle (number) -- yaw angle of the face (heading, turning head left or right),
  • smilingProbability (number) -- probability that the face is smiling,
  • leftEarPosition ({ x: number, y: number}) -- position of the left ear in view coordinates,
  • rightEarPosition ({ x: number, y: number}) -- position of the right ear in view coordinates,
  • leftEyePosition ({ x: number, y: number}) -- position of the left eye in view coordinates,
  • leftEyeOpenProbability (number) -- probability that the left eye is open,
  • rightEyePosition ({ x: number, y: number}) -- position of the right eye in view coordinates,
  • rightEyeOpenProbability (number) -- probability that the right eye is open,
  • leftCheekPosition ({ x: number, y: number}) -- position of the left cheek in view coordinates,
  • rightCheekPosition ({ x: number, y: number}) -- position of the right cheek in view coordinates,
  • mouthPosition ({ x: number, y: number}) -- position of the center of the mouth in view coordinates,
  • leftMouthPosition ({ x: number, y: number}) -- position of the left edge of the mouth in view coordinates,
  • rightMouthPosition ({ x: number, y: number}) -- position of the right edge of the mouth in view coordinates,
  • noseBasePosition ({ x: number, y: number}) -- position of the nose base in view coordinates.

smilingProbability, leftEyeOpenProbability and rightEyeOpenProbability are returned only if faceDetectionClassifications property is set to .all.

Positions of face landmarks are returned only if faceDetectionLandmarks property is set to .all.

See also FaceDetector component.

• faceDetectionMode (Camera.Constants.FaceDetection.Mode)

Mode of the face detection. Use one of Camera.Constants.FaceDetection.Mode.{fast, accurate}.

• faceDetectionLandmarks (Camera.Constants.FaceDetection.Landmarks)

Whether to detect landmarks on the faces. Use one of Camera.Constants.FaceDetection.Landmarks.{all, none}. See FaceDetector documentation for details.

• faceDetectionClassifications (Camera.Constants.FaceDetection.Classifications)

Whether to run additional classifications on the faces. Use one of Camera.Constants.FaceDetection.Classifications.{all, none}. See FaceDetector documentation for details.

• onMountError (function)

Callback invoked when camera preview could not been started. It is provided with an error object that contains a message.

• onBarCodeRead (function)

Callback that is invoked when a bar code has been successfully read. The callback is provided with an Object of the shape { type: string, data: string }, where the type refers to the bar code type that was scanned and the data is the information encoded in the bar code (in this case of QR codes, this is often a URL)

• barCodeTypes (Array)

An array of bar code types. Usage: Camera.Constants.BarCodeType.<codeType> where codeType is one of the listed above. Default: all supported bar code types. For example: barCodeTypes={[Camera.Constants.BarCodeType.qr]}

• useCamera2Api (boolean)

Android only. Whether to use Android's Camera2 API. See Note at the top of this page.

Methods

To use methods that Camera exposes one has to create a components ref and invoke them using it.

// ...
<Camera
  ref={ref => {
    this.camera = ref;
  }}
/>;
// ...
snap = async () => {
  if (this.camera) {
    let photo = await this.camera.takePictureAsync();
  }
};

takePictureAsync

Takes a picture and saves it to app's cache directory. Photos are rotated to match device's orientation and scaled to match the preview. Anyway on Android it is essential to set ratio prop to get a picture with correct dimensions.

Arguments

• options (object) --

  A map of options:

  • quality (number) -- Specify the quality of compression, from 0 to 1. 0 means compress for small size, 1 means compress for maximum quality.
  • base64 (boolean) -- Whether to also include the image data in Base64 format.
  • exif (boolean) -- Whether to also include the EXIF data for the image.

Returns

Returns a Promise that resolves to an object: { uri, width, height, exif, base64 } where uri is a URI to the local image file (useable as the source for an Image element) and width, height specify the dimensions of the image. base64 is included if the base64 option was truthy, and is a string containing the JPEG data of the image in Base64--prepend that with 'data:image/jpg;base64,' to get a data URI, which you can use as the source for an Image element for example. exif is included if the exif option was truthy, and is an object containing EXIF data for the image--the names of its properties are EXIF tags and their values are the values for those tags.

The local image URI is temporary. Use Expo.FileSystem.copyAsync to make a permanent copy of the image.

recordAsync

Starts recording a video that will be saved to cache directory. Videos are rotated to match device's orientation. Flipping camera during a recording results in stopping it.

Arguments

• options (object) --

  A map of options:

  • quality (VideoQuality) -- Specify the quality of recorded video. Usage: Camera.Constants.VideoQuality['<value>'], possible values: for 16:9 resolution 2160p, 1080p, 720p, 480p (Android only) and for 4:3 4:3 (the size is 640x480). If the chosen quality is not available for a device, the highest available is chosen.
  • maxDuration (number) -- Maximum video duration in seconds.
  • maxFileSize (number) -- Maximum video file size in bytes.
  • mute (boolean) -- If present, video will be recorded with no sound.

Returns

Returns a Promise that resolves to an object containing video file uri property. The Promise is returned if stopRecording was invoked, one of maxDuration and maxFileSize is reached or camera preview is stopped.

stopRecording

Stops recording if any is in progress.

getSupportedRatiosAsync

Android only. Get aspect ratios that are supported by the device and can be passed via ratio prop.

Returns

Returns a Promise that resolves to an array of strings representing ratios, eg. ['4:3', '1:1'].

Supported bar code formats

Bar code format	iOS	Android
aztec	Yes	Yes
codabar	No	Yes
code39	Yes	Yes
code93	Yes	Yes
code128	Yes	Yes
code138	Yes	No
code39mod43	Yes	No
datamatrix	Yes	Yes
ean13	Yes	Yes
ean8	Yes	Yes
interleaved2of5	Yes	No
itf14	Yes*	Yes
maxicode	No	Yes
pdf417	Yes	Yes
rss14	No	Yes
rssexpanded	No	Yes
upc_a	No	Yes
upc_e	Yes	Yes
upc_ean	No	Yes
qr	Yes	Yes

• sometimes when an ITF-14 barcode is recognized it's type is set to interleaved2of5.