field_of_view

A Flutter plugin to get the camera's field of view (FOV) on iOS and Android.

Features

• Get horizontal and vertical field of view angles from the back camera
• No camera permissions required
• Strongly-typed API using Pigeon
• Supports iOS and Android

Installation

Add this to your package's pubspec.yaml file:

dependencies:
  field_of_view: ^0.0.1

Usage

import 'package:field_of_view/field_of_view.dart';

final fov = FieldOfView();

try {
  final response = await fov.getFieldOfView();
  print('Horizontal FOV: ${response.horizontalFov}°');
  print('Vertical FOV: ${response.verticalFov}°');
} on PlatformException catch (e) {
  print('Error: ${e.message}');
}

Response

The FieldOfViewResponse contains:

Property	Type	Description
horizontalFov	double	Horizontal field of view in degrees
verticalFov	double	Vertical field of view in degrees

Note: The FOV values represent the camera sensor's native orientation (landscape), so horizontal FOV will typically be larger than vertical FOV, regardless of device orientation.

Platform-specific notes

iOS

Add the camera usage description to your app's Info.plist:

<key>NSCameraUsageDescription</key>
<string>This app needs camera access to determine the field of view.</string>

The plugin uses AVCaptureDevice to query camera characteristics. No runtime permission prompt is shown, but the usage description key must be present.

Android

No permissions required. The plugin uses Camera2 API's CameraCharacteristics to read static sensor metadata.

Error handling

The plugin throws PlatformException with the following error codes:

Code	Description
CAMERA_UNAVAILABLE	No back camera found on the device
SENSOR_UNAVAILABLE	Could not retrieve sensor size information
FOCAL_LENGTH_UNAVAILABLE	Could not retrieve focal length information

How it works

• iOS: Uses AVCaptureDevice.Format.geometricDistortionCorrectedVideoFieldOfView for horizontal FOV (corrected for lens distortion) and calculates vertical FOV from the aspect ratio. Requires iOS 13.0+.

• Android: Uses Camera2 API to read SENSOR_INFO_PHYSICAL_SIZE and LENS_INFO_AVAILABLE_FOCAL_LENGTHS from CameraCharacteristics, then calculates FOV using the pinhole camera model:

FOV = 2 × atan(sensorSize / (2 × focalLength))