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React Native

Real-time image & video resizing, automatic optimization, and file uploading in React Native using ImageKit.io.

This is a quick start guide to show you how to integrate ImageKit in a React Native app. The code samples covered here are hosted on Github - https://github.com/imagekit-samples/quickstart/tree/master/react-native.

This guide walks you through the following topics:

If you are new to React Native app development, you can learn about setting up the development environment and creating a new project here https://reactnative.dev/docs/environment-setup.

Setting up React Native app

For this tutorial, it is recommended to use the sample React Native app as shown below. If you already have an existing React Native app, it is also possible to use that, although you would need to modify the terminal commands and configurations in this tutorial as applicable.

Let's use the react-native-cli package to build a new project:

npx react-native@latest init imagekitReactNative

Navigate to the project directory:

cd imagekitReactNative/

Start the metro server.

npx react-native start

And now to run the app in the iOS simulator (you should have Xcode installed)

npm run ios

Or to run the app in the android simulator (you should have android studio installed)

npm run android

You should see the following screen. This means the sample app has been set up correctly.

Let's configure the components required for the application.

Execute the provided command to install the packages required for the application.

npm install @react-navigation/native @react-navigation/stack react-native-gesture-handler react-native-safe-area-context react-native-screens

In the sample app, we are using our own custom Button component created using React Native's components to ensure consistency.

app/components/Button/index.js
import React from 'react';
import {Text, TouchableOpacity} from 'react-native';
import getStyleSheet from './styles';

function Button(props) {
  let styleSheet = getStyleSheet(props.cssProps || {});
  return (
    <TouchableOpacity onPress={props.onPress} style={styleSheet.button}>
      <Text style={styleSheet.text}>{props.children}</Text>
    </TouchableOpacity>
  );
}

export default Button;

Create index.js and styles.js files within the app/screens/Main directory. These files will render & style buttons facilitating navigation to different screens, which will be developed in the subsequent sections. This configuration serves as our home screen.

app/screens/Main/index.js
import React from 'react';
import {View, Text} from 'react-native';
import Button from '../../components/Button/';
import getStyleSheet from './styles';

function Main({navigation}) {
  let styleSheet = getStyleSheet({});

  return (
    <>
      <View style={styleSheet.headContainer}>
        <Text style={styleSheet.text}>Imagekit Demo</Text>
      </View>
      <View style={styleSheet.btnContainer}>
        <View style={styleSheet.btnView}>
          <Button
            cssProps={styleSheet.buttonCssProps}
            onPress={() => navigation.navigate('Upload File')}>
            Upload File
          </Button>
        </View>
        <View style={styleSheet.btnView}>
          <Button
            cssProps={styleSheet.buttonCssProps}
            onPress={() => navigation.navigate('Fetch Images')}>
            Fetch Images
          </Button>
        </View>
        <View style={styleSheet.btnView}>
          <Button
            cssProps={styleSheet.buttonCssProps}
            onPress={() => navigation.navigate('Fetch Videos')}>
            Fetch Videos
          </Button>
        </View>
      </View>
    </>
  );
}

export default Main;

Create the AppComponent.js file within the app directory which will contain the screens. Add the home screen. Open the App.tsx file and add the provided code to render the AppComponent.

app/AppComponent.js
import React from 'react';
import {createStackNavigator} from '@react-navigation/stack';
import Main from './screens/Main';

const Stack = createStackNavigator();

function AppComponent() {
  return (
    <Stack.Navigator>
      <Stack.Screen name="Home" component={Main} />
    </Stack.Navigator>
  );
}
export default AppComponent;

It will look as shown below.

Setting up ImageKit JavaScript SDK

We will be using ImageKit JavaScript SDK. So let's install it.

npm install imagekit-javascript

imagekit-javascript SDK uses URL API to parse the URL internally. In React 16 and above, this API was removed, so if you are using React 16 or above, you will have to implement a small patch with these steps.

  1. Install the package with npm install react-native-url-polyfill

  2. Import the package in your app's entry point i.e. App.js like this import 'react-native-url-polyfill/auto'

Initializing the SDK

Create app/lib/imagekit.js file, this is where we will initialize our SDK and create helper functions that will be used in the app.

Also initialize the SDK with parameters set in the config file app/config/imagekit.js

app/config/imagekit.js
module.exports.urlEndpoint = ''; //insert your own url end point here
module.exports.publicKey = ''; //insert your own public key here
module.exports.authenticationEndpoint = ''; //your auth api path

Rendering Images

Image URL can be created from an image path or using the absolute image URL. You can learn more about it in docs.

To create a URL from the image source (full image URL), we can create a function like this, which takes the image source and a transformation array and returns the transformed image URL.

app/lib/imagekit.js
module.exports.getImagekitUrlFromSrc = function (imageSrc, transformationArray) {
  const ikOptions = {
    src: imageSrc,
    transformation: transformationArray,
  };
  const imageURL = imagekit.url(ikOptions);

  return imageURL;
};

To create a URL from the image path, we can create a helper function like this below.

app/lib/imagekit.js
module.exports.getImagekitUrlFromPath = function (
  imagePath,
  transformationArray,
  transformationPostion,
) {
  const ikOptions = {
    urlEndpoint,
    path: imagePath,
    transformation: transformationArray,
  };
  if (transformationPostion)
    ikOptions.transformationPostion = transformationPostion;

  const imageURL = imagekit.url(ikOptions);

  return imageURL;
};

The transformation position (path or query) is only valid when creating a URL from the image path. Transformations are always added as query parameters if the URL is created from an absolute image path using src.

Now, let's create app/screens/Fetch/index.js to fetch an image. Also, update app/AppComponent.js to include the fetch image screen.

app/AppComponent.js
import React from 'react';
import {createStackNavigator} from '@react-navigation/stack';

import Main from './screens/Main';
import Fetch from './screens/Fetch';

const Stack = createStackNavigator();

function AppComponent() {
  return (
    <Stack.Navigator>
      <Stack.Screen name="Home" component={Main} />
      <Stack.Screen name="Fetch Images" component={Fetch} />
    </Stack.Navigator>
  );
}

export default AppComponent;

It will look as shown below. In the sample app, the buttons are present to demonstrate the use of different transformations. You can see the full list of supported transformations here.

Common Image Manipulation

This section covers the basics:‌

ImageKit JavaScript SDK gives a name to each transformation parameter e.g. height for h and width for w parameter. It makes your code more readable. If the property does not match any of the available options, it is added as it is. See the full list of supported transformations in Javascript SDK on Github.

You can also use h and w parameter instead of height and width. See the complete list of transformations supported in ImageKit here.

Basic Image Resizing

Let's resize the image to a height of 150 and a width of 150.

Note: You'll need to specify height and width in the Image component of react-native accordingly as we are fetching the image from a remote url.

app/screens/Fetch/index.js
function showTransformedImage() {
  let transformedImageUrl = getImagekitUrlFromSrc(imageSrc, [
    {
      height: 150,
      width: 150,
    },
  ]);
  setImageUrl(transformedImageUrl);
}

Output :

Crop Mode

Let’s now see how crop mode work. We will try the pad_resize crop strategy.

In this strategy, the output image's dimension (height and width) is the same as requested, no cropping occurs, and the aspect ratio is preserved. This is accomplished by adding padding around the output image to get it to match the exact dimension as requested. You can read more about this here.

app/screens/Fetch/index.js
function showTransformedImage() {
  let transformedImageUrl = getImagekitUrlFromSrc(imageSrc, [
    {
      height: 200,
      width: 300,
      cropMode: 'pad_resize',
      background: 'F3F3F3',
    },
  ]);
  setImageUrl(transformedImageUrl);
}

Output :

Aspect Ratio

You can use the ar parameter to change the aspect ratio like this

app/screens/Fetch/index.js
function showTransformedImage() {
  let transformedImageUrl = getImagekitUrlFromSrc(imageSrc, [
    {
      height: 400,
      aspectRatio: '3-2',
    },
  ]);
  setImageUrl(transformedImageUrl);
}

Output :

Chained Transformation

Chained transformations provide a simple way to control the sequence in which transformations are applied.

Let’s try it out by resizing an image, then rotating it:

app/screens/Fetch/index.js
function showTransformedImage() {
  let transformedImageUrl = getImagekitUrlFromSrc(imageSrc, [
    {
      height: 300,
      width: 300,
    },
    {
      rotation: '90',
    },
  ]);
  setImageUrl(transformedImageUrl);
}

Output :

Adding overlays

ImageKit.io enables you to apply overlays to images and videos using the raw parameter with the concept of layers. The raw parameter facilitates incorporating transformations directly in the URL. A layer is a distinct type of transformation that allows you to define an asset to serve as an overlay, along with its positioning and additional transformations.

Text Overlay

Text overlay can be used to place text on an image. Here's how:

app/screens/Fetch/index.js
function showTransformedImage() {
  let transformedImageUrl = getImagekitUrlFromSrc(imageSrc, [
    {
      raw: 'l-text,i-Imagekit,co-0651D5,fs-50,l-end',
    },
  ]);
  setImageUrl(transformedImageUrl);
}

Output :

Image Overlay

Image overlay can be used like this:

app/screens/Fetch/index.js
function showTransformedImage() {
  let transformedImageUrl = getImagekitUrlFromSrc(imageSrc, [
    {
      raw: 'l-image,i-plant.jpeg,h-100,b-10_CDDC39,l-end',
    },
  ]);
  setImageUrl(transformedImageUrl);
}

Output :

Client-side file uploading

Let's learn how to upload an image to our media library.

For this, we would need a dummy backend app to authenticate our upload request. API authentication for upload always happens on the backend for security reasons.

In the following section, we will create a backend server that we can use.

Setting up the backend app

For this quickstart guide, we will create a sample Node.js server which will provide an authentication endpoint at http://localhost:8080/auth.

Let's create a file index.js inside server folder in the project root.

mkdir server
touch server/index.js

Install the basic packages needed to create a dummy server for ImageKit backend authentication:

npm install express uuid cors

We will use the ImageKit Node.js SDK to implement http://localhost:8080/auth.

The backend SDK requires your API public key, private key, and URL endpoint. You can obtain them from Developer Options and URL-endpoint pages respectively.

This is how server/index.js file should look now.

server/index.js
const express = require('express');
const router = express.Router();
const cors = require('cors');
const app = express();
app.use(cors());

const uuid = require('uuid');
const crypto = require('crypto');

const privateKey = ''; //insert your own private key here
router.get('/auth', function (req, res) {
  const token = req.query.token || uuid.v4();
  const expire = req.query.expire || parseInt(Date.now() / 1000) + 2400;
  const privateAPIKey = `${privateKey}`;
  const signature = crypto
    .createHmac('sha1', privateAPIKey)
    .update(token + expire)
    .digest('hex');
  res.status(200);
  res.send({
    token,
    expire,
    signature,
  });
});

app.use('/', router);

app.listen(8080, function () {
  console.log('Live at Port 8080');
});

Obtain your API private key from the developer section from the ImageKit dashboard, and paste it in the server index.js file.

Let's run the backend server.

cd server
node index.js

You should see a log saying that the app is 'Live at port 8080'.

If you GET http://localhost:8080/auth, you should see a JSON response like this. Actual values will vary.

{
    token: "5dd0e211-8d67-452e-9acd-954c0bd53a1f",
    expire: 1601047259,
    signature: "dcb8e72e2b6e98186ec56c62c9e62886f40eaa96"
}

Configure the auth endpoint in the frontend app

Head over to app/config/imagekit.js and replace the authenticationEndpoint with http://localhost:8080/auth

Upload an image

Try using react-native v0.73.0 which is the latest version at the time of writing this article, as some of the previous versions have a known issue in uploading files. If you are using a previous version and can't upgrade, you'll have to implement a workaround.

For this, let's create couple of functions in app/lib/imagekit.js file and update app/AppComponent.js to include the upload screen.

app/lib/imagekit.js
const authenticator = async () => {
  try {
    // You can pass headers as well and later validate the request source in the backend, or you can use headers for any other use case.
    const response = await fetch(authenticationEndpoint);
    if (!response.ok) {
      const errorText = await response.text();
      throw new Error(
        `Request failed with status ${response.status}: ${errorText}`,
      );
    }
    const data = await response.json();
    const {signature, expire, token} = data;
    return {signature, expire, token};
  } catch (error) {
    throw new Error(`Authentication request failed: ${error.message}`);
  }
};

module.exports.uploadFile = async function (file) {
  const res = await authenticator();
  return new Promise((resolve, reject) => {
    imagekit.upload(
      {
        file,
        fileName: file.name, //you can change this and generate your own name if required
        tags: ['sample-tag-1', 'sample-tag-2'], //change this or remove it if you want
        ...res,
      },
      function (err, result) {
        if (err) reject(err);
        resolve(result);
      },
    );
  });
};

We are going to use react-native-document-picker to select files.

npm install react-native-document-picker

This is how we implement file upload in app/screens/Upload/index.js

app/screens/Upload/index.js
import React, {useState} from 'react';
import {View} from 'react-native';
import DocumentPicker from 'react-native-document-picker';

import Button from '../../components/Button/';
import Text from '../../components/Text/';
import getStyleSheet from './styles';

import {uploadFile} from '../../lib/imagekit';

function Upload() {
  let styleSheet = getStyleSheet({});

  const [uploadFileUrl, setUploadFileUrl] = useState();

  async function openFileSelector() {
    try {
      const res = await DocumentPicker.pick({
        type: [DocumentPicker.types.allFiles],
      });

      uploadFileToImagekit(res);
    } catch (err) {
      if (DocumentPicker.isCancel(err)) {
        // User cancelled the picker, exit any dialogs or menus and move on
      } else {
        throw err;
      }
    }
  }

  async function uploadFileToImagekit(fileData) {
    try {
      const uploadedFile = await uploadFile(fileData);
      setUploadFileUrl(uploadedFile.url);
    } catch (err) {
      //handle error in uploading file
    }
  }

  return (
    <>
      <View style={styleSheet.container}>
        <Button
          cssProps={styleSheet.buttonCssProps}
          onPress={() => openFileSelector()}>
          Upload File
        </Button>
        <View style={styleSheet.captionView}>
          {uploadFileUrl && <Text>Uploaded File - {uploadFileUrl}</Text>}
        </View>
      </View>
    </>
  );
}

export default Upload;

Let’s upload an image by selecting a file using the file input.

The uploader uploads whenever file input changes. You can verify that file was successfully uploaded by checking the browser console. It should print the file URL.

After a successful upload, you should see the newly uploaded file in the Media Library of your ImageKit dashboard.

If you don't see the file, check if there are any errors in the log. Make sure that the private API key has been configured. The server app is running. And the uploaded file type is supported by ImageKit.

Rendering videos

Rendering videos works similarly to rendering images.

We're going to use the react-native-video package to play video files, but you can use any other video player.

npm install react-native-video

Update the app/screens/Videos/index.js and app/AppComponent.js file to fetch video.

app/screens/Videos/index.js
import React from 'react';
import {View, ScrollView, Text} from 'react-native';
import getStyleSheet from './styles';
import {getImagekitUrlFromSrc} from '../../lib/imagekit';
import {urlEndpoint} from '../../config/imagekit';
import Video from 'react-native-video';

function Videos() {
  let styleSheet = getStyleSheet({});

  const videoPath = '/sample-video.mp4';
  let videoSrc = urlEndpoint + videoPath;

  function showTransformedVideo(transformationType) {
    let transformationArray = [];
    let transformedVideoUrl;

    switch (transformationType) {
      case 'Transformation 1': //basic video resizing
        transformationArray = [
          {
            height: 200,
            width: 200,
          },
        ];
        transformedVideoUrl = getImagekitUrlFromSrc(
          videoSrc,
          transformationArray,
        );
        break;

      case 'Transformation 2': //crop mode and url from source
        videoSrc = 'https://ik.imagekit.io/demo/img/sample-video.mp4';
        transformationArray = [
          {
            b: '5_red',
            q: 95,
          },
        ];
        transformedVideoUrl = getImagekitUrlFromSrc(
          videoSrc,
          transformationArray,
        );
        break;

      default:
        transformedVideoUrl = getImagekitUrlFromSrc(videoSrc, []);
        break;
    }

    return transformedVideoUrl;
  }

  return (
    <ScrollView>
      <View style={styleSheet.imgContainer}>
        <>
          <View style={styleSheet.captionView}>
            <Text style={styleSheet.text}>{'Transformation 1'}</Text>
          </View>
          <View style={styleSheet.captionView}>
            <Text style={styleSheet.text}>
              Rendered URL - {showTransformedVideo('Transformation 1')}
            </Text>
          </View>
          <Video
            source={{uri: showTransformedVideo('Transformation 1')}}
            style={{
              width: 200,
              height: 200,
            }}
            controls={true}
          />
        </>
      </View>
      <View style={styleSheet.imgContainer}>
        <>
          <View style={styleSheet.captionView}>
            <Text style={styleSheet.text}>{'Transformation 2'}</Text>
          </View>
          <View style={styleSheet.captionView}>
            <Text style={styleSheet.text}>
              Rendered URL - {showTransformedVideo('Transformation 2')}
            </Text>
          </View>
          <Video
            source={{uri: showTransformedVideo('Transformation 2')}}
            style={{
              width: 300,
              height: 300,
            }}
            controls={true}
          />
        </>
      </View>
    </ScrollView>
  );
}

export default Videos;

It will look as shown below.

What's next

The possibilities for image manipulation and optimization with ImageKit are endless. Learn more about it here:

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