React-Native: Convert image url to base64 string

Question

I\'m building a react native app that needs to store images at base64 string format for offline viewing capabilities.

What library / function would give me the best

Answer 1

You can use react-native-image-base64. You have to give image url and it returns the base64 string of image.

ImgToBase64.getBase64String('file://youfileurl')
  .then(base64String => doSomethingWith(base64String))
  .catch(err => doSomethingWith(err));

Answer 2

The standalone expo FileSystem package makes this simple:

const base64 = await FileSystem.readAsStringAsync(photo.uri, { encoding: 'base64' });

• https://docs.expo.io/versions/latest/sdk/filesystem/
• https://github.com/expo/expo/tree/master/packages/expo-file-system

As 2019-09-27 this package handles both file:// and content:// uri's

Answer 3

There is a better way: Install this react-native-fs, IF you don't already have it.

import RNFS from 'react-native-fs';

RNFS.readFile(this.state.imagePath, 'base64')
.then(res =>{
  console.log(res);
});

Answer 4

To convert image to base64 in React native, the FileReader utility is helpful:

const fileReader = new FileReader();
fileReader.onload = fileLoadedEvent => {
  const base64Image = fileLoadedEvent.target.result;
};
fileReader.readAsDataURL(imagepath); 

This requires react-native-file.

Another alternative, and probably the preferred alternative, is to use NativeModules. The Medium article shows how. It requires creating a native module.

NativeModules.ReadImageData.readImage(path, (base64Image) => {
  // Do something here.
});

Answer 5

I use rn-fetch-blob, basically it provides lot of file system and network functions make transferring data pretty easy.

react-native-fetch-blob is deprecated

import RNFetchBlob from "rn-fetch-blob";
const fs = RNFetchBlob.fs;
let imagePath = null;
RNFetchBlob.config({
  fileCache: true
})
  .fetch("GET", "http://www.example.com/image.png")
  // the image is now dowloaded to device's storage
  .then(resp => {
    // the image path you can use it directly with Image component
    imagePath = resp.path();
    return resp.readFile("base64");
  })
  .then(base64Data => {
    // here's base64 encoded image
    console.log(base64Data);
    // remove the file from storage
    return fs.unlink(imagePath);
  });

source Project Wiki

Answer 6

I used another package: react-native-fs

import RNFS from 'react-native-fs';

var data = await RNFS.readFile( "file://path-to-file", 'base64').then(res => { return res });

This works fine.