Merge pull request #87 from Greg-Bush/master

useImageDimensions

Author: LinusU

README.md

@@ -26,6 +26,7 @@ yarn add @react-native-community/hooks
 - [useCameraRoll](https://github.com/react-native-community/hooks#usecameraroll)
 - [useClipboard](https://github.com/react-native-community/hooks#useclipboard)
 - [useDimensions](https://github.com/react-native-community/hooks#usedimensions)
+- [useImageDimensions](https://github.com/react-native-community/hooks#useImageDimensions)
 - [useKeyboard](https://github.com/react-native-community/hooks#usekeyboard)
 - [useInteractionManager](https://github.com/react-native-community/hooks#useinteractionmanager)
 - [useDeviceOrientation](https://github.com/react-native-community/hooks#usedeviceorientation)
@@ -104,6 +105,23 @@ const { width, height } = useDimensions().window
 const screen = useDimensions().screen
 ```
 
+### `useImageDimensions`
+
+```js
+import {useImageDimensions} from '@react-native-community/hooks'
+
+const source = require('./assets/yourImage.png')
+// or
+const source = {uri: 'https://your.image.URI'}
+
+const {dimensions, loading, error} = useImageDimensions(source)
+
+if(loading || error || !dimensions) {
+  return null
+}
+const {width, height, aspectRatio} = dimensions
+```
+
 ### `useKeyboard`
 
 ```js

src/index.ts

@@ -8,6 +8,7 @@ import {useKeyboard} from './useKeyboard'
 import {useInteractionManager} from './useInteractionManager'
 import {useDeviceOrientation} from './useDeviceOrientation'
 import {useLayout} from './useLayout'
+import {useImageDimensions} from './useImageDimensions'
 
 export {
   useDimensions,
@@ -20,4 +21,5 @@ export {
   useInteractionManager,
   useDeviceOrientation,
   useLayout,
+  useImageDimensions,
 }

src/useImageDimensions.ts

@@ -0,0 +1,59 @@
+import {useEffect, useState} from 'react'
+import {Image, ImageRequireSource} from 'react-native'
+
+export interface URISource {
+  uri: string
+}
+
+export type Source = ImageRequireSource | URISource
+
+export interface ImageDimensions {
+  dimensions?: {width: number; height: number; aspectRatio: number}
+  error?: Error
+  loading: boolean
+}
+
+/**
+ * @param source either a remote URL or a local file resource.
+ * @returns original image dimensions (width, height and aspect ratio).
+ */
+export function useImageDimensions(source: Source): ImageDimensions {
+  const [result, setResult] = useState<ImageDimensions>({loading: true})
+
+  useEffect(() => {
+    try {
+      if (typeof source === 'number') {
+        const {width, height} = Image.resolveAssetSource(source)
+
+        setResult({
+          dimensions: {width, height, aspectRatio: width / height},
+          loading: false,
+        })
+
+        return
+      }
+
+      if (typeof source === 'object' && source.uri) {
+        setResult({loading: true})
+
+        Image.getSize(
+          source.uri,
+          (width, height) =>
+            setResult({
+              dimensions: {width, height, aspectRatio: width / height},
+              loading: false,
+            }),
+          (error) => setResult({error, loading: false}),
+        )
+
+        return
+      }
+
+      throw new Error('not implemented')
+    } catch (error) {
+      setResult({error, loading: false})
+    }
+  }, [source])
+
+  return result
+}