127 lines
4.8 KiB
Markdown
127 lines
4.8 KiB
Markdown
<table>
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<tr>
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<th><a href="../README.md">README</a></th>
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<th><a href="./SETUP.md">SETUP</a></th>
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<th>DEVICES</th>
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<th><a href="./FORMATS.md">FORMATS</a></th>
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<th><a href="./FRAME_PROCESSORS.md">FRAME_PROCESSORS</a></th>
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<th><a href="./ANIMATED.md">ANIMATED</a></th>
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<th><a href="./ERRORS.md">ERRORS</a></th>
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</tr>
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</table>
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<br/>
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<h1 align="center">Devices</h1>
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<div>
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<img align="right" width="35%" src="../img/ultra-wide-demo.gif">
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</div>
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### What are camera devices?
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Camera devices are the physical (or "virtual") devices that can be used to record videos or capture photos.
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* **Physical**: A physical camera device is a **camera lens on your phone**. Different physical camera devices have different specifications, such as different capture formats, field of views, focal lengths, and more. Some phones have multiple physical camera devices.
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> Examples: _"Backside Wide-Angle Camera"_, _"Frontside Wide-Angle Camera (FaceTime HD)"_, _"Ultra-Wide-Angle back camera"_.
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* **Virtual**: A virtual camera device is a **combination of one or more physical camera devices**, and provides features such as _virtual-device-switchover_ while zooming or _combined photo delivery_ from all physiscal cameras to produce higher quality images.
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> Examples: _"Triple-Camera"_, _"Dual-Wide-Angle Camera"_
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### Get available camera devices
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To get a list of all available camera devices, use the `getAvailableCameraDevices` function:
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```ts
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const devices = await Camera.getAvailableCameraDevices()
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```
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> [🔗 See the `CameraDevice` type](./../src/CameraDevice.ts)
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A camera device (`CameraDevice`) contains a list of physical device types this camera device consists of.
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Example:
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* For a single Wide-Angle camera, this would be `["wide-angle-camera"]`
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* For a Triple-Camera, this would be `["wide-angle-camera", "ultra-wide-angle-camera", "telephoto-camera"]`
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You can use the helper function `parsePhysicalDeviceTypes` to convert a list of physical devices to a single device descriptor type which can also describe virtual devices:
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```ts
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console.log(device.devices)
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// --> ["wide-angle-camera", "ultra-wide-angle-camera", "telephoto-camera"]
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const deviceType = parsePhysicalDeviceTypes(device.devices)
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console.log(deviceType)
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// --> "triple-camera"
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```
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The `CameraDevice` type also contains other useful information describing a camera device, such as `position` ("front", "back", ...), `hasFlash`, it's `formats` (See [FORMATS.md](./FORMATS.md)), and more.
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Make sure to carefully filter out unneeded camera devices, since not every phone supports all camera device types. Some phones don't even have front-cameras.
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### `useCameraDevices` hook
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The react-native-vision-camera library provides a hook to make camera device selection a lot easier.
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You can specify a device type to only find devices with the given type:
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```tsx
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function App() {
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const devices = useCameraDevices('wide-angle-camera')
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const device = devices.back
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return (
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<Camera
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style={StyleSheet.absoluteFill}
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device={device}
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/>
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)
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}
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```
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Or just return the "best matching camera device". This function prefers camera devices with more physical cameras, and always ranks "wide-angle" physical camera devices first.
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> Example: `triple-camera` > `dual-wide-camera` > `dual-camera` > `wide-angle-camera` > `ultra-wide-angle-camera` > `telephoto-camera` > ...
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```tsx
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function App() {
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const devices = useCameraDevices()
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const device = devices.back
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return (
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<Camera
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style={StyleSheet.absoluteFill}
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device={device}
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/>
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)
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}
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```
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### The `isActive` prop
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The Camera's `isActive` property can be used to _pause_ the session (`isActive={false}`) while still keeping the session "warm". This is more desirable than completely unmounting the camera, since _resuming_ the session (`isActive={true}`) will be **much faster** than re-mounting the camera view.
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For example, you want to **pause the camera** when the user **navigates to another page** or **minimizes the app** since otherwise the camera continues to run in the background without the user seeing it, causing **siginificant battery drain**. Also, on iOS a green dot indicates the user that the camera is still active, possibly causing the user to raise privacy concerns. (🔗 See ["About the orange and green indicators in your iPhone status bar"](https://support.apple.com/en-us/HT211876))
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This example demonstrates how you could pause the camera stream once the app goes into background using a custom `useIsAppForeground` hook:
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```tsx
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function App() {
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const devices = useCameraDevices()
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const device = devices.back
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const isAppForeground = useIsAppForeground()
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return (
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<Camera
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style={StyleSheet.absoluteFill}
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device={device}
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isActive={isAppForeground}
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/>
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)
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}
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```
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> Note: If you don't care about fast resume times you can also fully unmount the `<Camera>` view instead, which will use a lot less memory (RAM).
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