95 lines
4.6 KiB
Plaintext
95 lines
4.6 KiB
Plaintext
---
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id: animated
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title: Zooming with Reanimated
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sidebar_label: Zooming with Reanimated
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---
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import useBaseUrl from '@docusaurus/useBaseUrl';
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<div>
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<svg xmlns="http://www.w3.org/2000/svg" width="283" height="535" style={{ float: 'right' }}>
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<image href={useBaseUrl("img/demo.gif")} x="18" y="33" width="247" height="469" />
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<image href={useBaseUrl("img/frame.png")} width="283" height="535" />
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</svg>
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</div>
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## Animations
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Often you'd want to animate specific props in the Camera. For example, if you'd want to create a custom zoom gesture, you can smoothly animate the Camera's `zoom` property.
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The `<Camera>` component already provides a natively implemented zoom gesture which you can enable with the [`enableZoomGesture`](/docs/api/interfaces/cameraprops.cameraprops-1#enablezoomgesture) prop. This does not require any additional work, but if you want to setup a custom gesture, such as the one in Snapchat or Instagram where you move up your finger while recording, continue reading.
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### Animation libraries
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While you can use any animation library to animate the `zoom` property (or use no animation library at all) it is recommended to use [react-native-reanimated](https://github.com/software-mansion/react-native-reanimated) (v2) to achieve best performance. Head over to their [Installation guide](https://docs.swmansion.com/react-native-reanimated/docs/installation) to install Reanimated if you haven't already.
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### Implementation
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The following example implements a button which smoothly zooms to a random value using [react-native-reanimated](https://github.com/software-mansion/react-native-reanimated):
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```tsx
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import Reanimated, {
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useAnimatedProps,
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useSharedValue,
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withSpring,
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} from "react-native-reanimated"
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const ReanimatedCamera = Reanimated.createAnimatedComponent(Camera)
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Reanimated.addWhitelistedNativeProps({
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zoom: true,
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})
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export function App() {
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const devices = useCameraDevices()
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const device = devices.back
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const zoom = useSharedValue(0)
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const onRandomZoomPress = useCallback(() => {
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zoom.value = withSpring(Math.random())
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}, [])
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const animatedProps = useAnimatedProps<Partial<CameraProps>>(
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() => ({ zoom: zoom.value }),
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[zoom]
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)
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if (device == null) return <LoadingView />
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return (
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<>
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<ReanimatedCamera
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style={StyleSheet.absoluteFill}
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device={device}
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isActive={true}
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animatedProps={animatedProps}
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/>
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<TouchableOpacity
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style={styles.zoomButton}
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onPress={onRandomZoomPress}>
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<Text>Zoom randomly!</Text>
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</TouchableOpacity>
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</>
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)
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}
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```
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### Explanation
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1. The `Camera` was made animatable using `Reanimated.createAnimatedComponent`
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2. The `zoom` property is added to the whitelisted native props to make it animatable.
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> Note that this might not be needed in the future, see: [reanimated#1409](https://github.com/software-mansion/react-native-reanimated/pull/1409)
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3. Using [`useSharedValue`](https://docs.swmansion.com/react-native-reanimated/docs/api/useSharedValue), we're creating a shared value that holds the value for the `zoom` property.
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4. Using the [`useAnimatedProps`](https://docs.swmansion.com/react-native-reanimated/docs/api/useAnimatedProps) hook, we apply the shared value to Camera's `zoom` property.
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5. We apply the animated props to the `ReanimatedCamera` component's `animatedProps` property.
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### Logarithmic scale
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A Camera's `zoom` property is represented in a **logarithmic scale**. That means, increasing from `0` to `0.1` will appear to be a much larger offset than increasing from `0.9` to `1`. If you want to implement a zoom gesture (`<PinchGestureHandler>`, `<PanGestureHandler>`), try to flatten the `zoom` property to a **linear scale** by raising it **exponentially**. (`zoom.value ** 2`)
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### Pinch-to-zoom
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The above example only demonstrates how to animate the `zoom` property. To actually implement pinch-to-zoom or pan-to-zoom, take a look at the [VisionCamera example app](https://github.com/cuvent/react-native-vision-camera/tree/main/example), the pinch-to-zoom gesture can be found [here](https://github.com/cuvent/react-native-vision-camera/blob/d8551792e97eaa6fa768f54059ffce054bf748d9/example/src/CameraPage.tsx#L162-L176), and the pan-to-zoom gesture can be found [here](https://github.com/cuvent/react-native-vision-camera/blob/d8551792e97eaa6fa768f54059ffce054bf748d9/example/src/views/CaptureButton.tsx#L185-L205). They implement a real world use-case, where the maximum zoom value is clamped to a realistic value, and the zoom responds very gracefully by using a logarithmic scale.
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<br />
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#### 🚀 Next section: [Camera Errors](errors)
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