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Expo ImageManipulator iconExpo ImageManipulator

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A library that provides an API for image manipulation on the local file system.

Android
iOS
Web

expo-image-manipulator provides an API to modify images stored on the local file system.

Installation

Terminal
- npx expo install expo-image-manipulator

If you are installing this in an existing React Native app, start by installing expo in your project. Then, follow the additional instructions as mentioned by the library's README under "Installation in bare React Native projects" section.

Usage

This will first rotate the image 90 degrees clockwise, then flip the rotated image vertically and save it as a PNG.

Basic ImageManipulator usage
import { useState, useEffect } from 'react';
import { Button, Image, StyleSheet, View } from 'react-native';
import { Asset } from 'expo-asset';
import { manipulateAsync, FlipType, SaveFormat } from 'expo-image-manipulator';

export default function App() {
  const [ready, setReady] = useState(false);
  const [image, setImage] = useState(null);

  useEffect(() => {
    (async () => {
      const image = Asset.fromModule(require('./assets/snack-icon.png'));
      await image.downloadAsync();
      setImage(image);
      setReady(true);
    })();
  }, []);

  const _rotate90andFlip = async () => {
    const manipResult = await manipulateAsync(
      image.localUri || image.uri,
      [{ rotate: 90 }, { flip: FlipType.Vertical }],
      { compress: 1, format: SaveFormat.PNG }
    );
    setImage(manipResult);
  };

  const _renderImage = () => (
    <View style={styles.imageContainer}>
      <Image source={{ uri: image.localUri || image.uri }} style={styles.image} />
    </View>
  );

  return (
    <View style={styles.container}>
      {ready && image && _renderImage()}
      <Button title="Rotate and Flip" onPress={_rotate90andFlip} />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
  },
  imageContainer: {
    marginVertical: 20,
    alignItems: 'center',
    justifyContent: 'center',
  },
  image: {
    width: 300,
    height: 300,
    resizeMode: 'contain',
  },
});

API

import * as ImageManipulator from 'expo-image-manipulator';

Methods

ImageManipulator.manipulateAsync(uri, actions, saveOptions)

ParameterTypeDescription
uristring

URI of the file to manipulate. Should be on the local file system or a base64 data URI.

actions
(optional)		Action[]

An array of objects representing manipulation options. Each object should have only one of the keys that corresponds to specific transformation.

Default:[]
saveOptions
(optional)		SaveOptions

A map defining how modified image should be saved.

Default:{}

Manipulate the image provided via uri. Available modifications are rotating, flipping (mirroring), resizing and cropping. Each invocation results in a new file. With one invocation you can provide a set of actions to perform over the image. Overwriting the source file would not have an effect in displaying the result as images are cached.

Returns:

Promise<ImageResult>

Promise which fulfils with ImageResult object.

Types

Action

Literal Type: multiple types

Acceptable values are: ActionResize | ActionRotate | ActionFlip | ActionCrop | ActionExtent

ActionCrop

NameTypeDescription
crop{ height: number, originX: number, originY: number, width: number }

Fields specify top-left corner and dimensions of a crop rectangle.

ActionExtent

NameTypeDescription
extent{ backgroundColor: string | null, height: number, originX: number, originY: number, width: number }
Only for: 
Web

Set the image size and offset. If the image is enlarged, unfilled areas are set to the backgroundColor. To position the image, use originX and originY.

ActionFlip

NameTypeDescription
flipFlipType

An axis on which image will be flipped. Only one flip per transformation is available. If you want to flip according to both axes then provide two separate transformations.

ActionResize

NameTypeDescription
resize{ height: number, width: number }

Values correspond to the result image dimensions. If you specify only one value, the other will be calculated automatically to preserve image ratio.

ActionRotate

NameTypeDescription
rotatenumber

Degrees to rotate the image. Rotation is clockwise when the value is positive and counter-clockwise when negative.

ImageResult

NameTypeDescription
base64
(optional)		string

It is included if the base64 save option was truthy, and is a string containing the JPEG/PNG (depending on format) data of the image in Base64. Prepend that with 'data:image/xxx;base64,' to get a data URI, which you can use as the source for an Image element for example (where xxx is jpeg or png).

heightnumber

Height of the image or video.

uristring

An URI to the modified image (usable as the source for an Image or Video element).

widthnumber

Width of the image or video.

SaveOptions

A map defining how modified image should be saved.

NameTypeDescription
base64
(optional)		boolean

Whether to also include the image data in Base64 format.

compress
(optional)		number

A value in range 0.0 - 1.0 specifying compression level of the result image. 1 means no compression (highest quality) and 0 the highest compression (lowest quality).

format
(optional)		SaveFormat

Specifies what type of compression should be used and what is the result file extension. SaveFormat.PNG compression is lossless but slower, SaveFormat.JPEG is faster but the image has visible artifacts. Defaults to SaveFormat.JPEG

Enums

FlipType

FlipType Values

Horizontal

FlipType.Horizontal ＝ "horizontal"

Vertical

FlipType.Vertical ＝ "vertical"

SaveFormat

SaveFormat Values

JPEG

SaveFormat.JPEG ＝ "jpeg"

PNG

SaveFormat.PNG ＝ "png"

WEBP

SaveFormat.WEBP ＝ "webp"