react-native-vision-camera/docs/docs/guides/ZOOMING.mdx

---
id: zooming
title: Zooming
sidebar_label: Zooming
---

import useBaseUrl from '@docusaurus/useBaseUrl';

<div>
  <svg xmlns="http://www.w3.org/2000/svg" width="283" height="535" style={{ float: 'right' }}>
    <image href={useBaseUrl("img/demo.gif")} x="18" y="33" width="247" height="469"  />
    <image href={useBaseUrl("img/frame.png")} width="283" height="535" />
  </svg>
</div>

The `<Camera>` component already provides a natively implemented zoom gesture which you can enable with the [`enableZoomGesture`](/docs/api/interfaces/CameraProps#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.

### Animation libraries

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.

### Implementation

#### Overview

1. Make the Camera View animatable using `createAnimatedComponent`
2. Make the Camera's `zoom` property animatable using `addWhitelistedNativeProps`
3. Create a SharedValue using [`useSharedValue`](https://docs.swmansion.com/react-native-reanimated/docs/api/useSharedValue) which represents the zoom state (from `0` to `1`)
4. Use [`useAnimatedProps`](https://docs.swmansion.com/react-native-reanimated/docs/api/useAnimatedProps) to map the zoom SharedValue to the zoom property.
5. We apply the animated props to the `ReanimatedCamera` component's `animatedProps` property.

#### Code

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):

```tsx
import Reanimated, {
  useAnimatedProps,
  useSharedValue,
  withSpring,
} from "react-native-reanimated"

const ReanimatedCamera = Reanimated.createAnimatedComponent(Camera)
Reanimated.addWhitelistedNativeProps({
  zoom: true,
})

export function App() {
  const devices = useCameraDevices()
  const device = devices.back
  const zoom = useSharedValue(0)

  const onRandomZoomPress = useCallback(() => {
    zoom.value = withSpring(Math.random())
  }, [])

  const animatedProps = useAnimatedProps<Partial<CameraProps>>(
    () => ({ zoom: zoom.value }),
    [zoom]
  )

  if (device == null) return <LoadingView />
  return (
    <>
      <ReanimatedCamera
        style={StyleSheet.absoluteFill}
        device={device}
        isActive={true}
        animatedProps={animatedProps}
      />
      <TouchableOpacity
        style={styles.zoomButton}
        onPress={onRandomZoomPress}>
        <Text>Zoom randomly!</Text>
      </TouchableOpacity>
    </>
  )
}
```

### Min, Max and Neutral Zoom

A Camera device has different minimum, maximum and neutral zoom values. Those values are expressed through the `CameraDevice`'s [`minZoom`](/docs/api/interfaces/CameraDevice#minzoom), [`maxZoom`](/docs/api/interfaces/CameraDevice#maxzoom) and [`neutralZoom`](/docs/api/interfaces/CameraDevice#neutralzoom) props, and are represented in "scale". So if the `maxZoom` property of a device is `2`, that means the view can be enlarged by twice it's zoom, aka the viewport halves.

* The `minZoom` value is always `1`.
* The `maxZoom` value can have very high values (such as `128`), but often you want to clamp this value to something realistic like `16`.
* The `neutralZoom` value is often `1`, but can be larger than `1` for devices with "fish-eye" (ultra-wide-angle) cameras. In those cases, the user expects to be at whatever zoom value `neutralZoom` is (e.g. `2`) per default, and if he tries to zoom out even more, he goes to `minZoom` (`1`), which switches over to the "fish-eye" (ultra-wide-angle) camera as seen in this GIF:

<div align="center">
  <img src="https://developer.android.com/images/training/camera/multi-camera-4.gif" width="45%" />
</div>

The Camera's `zoom` property expects values to be in the same "factor" scale as the `minZoom`, `neutralZoom` and `maxZoom` values - so if you pass `zoom={device.minZoom}` it is at the minimum available zoom, where as if you pass `zoom={device.maxZoom}` the maximum zoom value possible is zoomed in. It is recommended that you start at `device.neutralZoom` and let the user manually zoom out to the fish-eye camera on demand (if available).

### Logarithmic scale

A Camera's `zoom` property is represented in a **logarithmic scale**. That means, increasing from `1` to `2` will appear to be a much larger offset than increasing from `127` to `128`. 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`)

### Pinch-to-zoom

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/mrousavy/react-native-vision-camera/tree/main/example), the pinch-to-zoom gesture can be found [here](https://github.com/mrousavy/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/mrousavy/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.

<br />

#### 🚀 Next section: [Focusing](focusing)