iOS

This quickstart guide shows you how to integrate ImageKit into an iOS application. The code samples covered are available on Github: https://github.com/imagekit-samples/quickstart/tree/master/ios.

This guide walks you through the following topics: ‌

• Clone and run the tutorial app
• Setting up ImageKit iOS SDK
• Rendering images
• Applying common image manipulations
• Adding overlays to images
• Client-side file uploading
• Setting an upload policy
• How to preprocess your files before uploading

For this tutorial, it is recommended to use the sample iOS app, as shown below. If you already have an existing iOS app, it is also possible to use that, which will be explained in the continuation of the sample app.

git clone 
https://github.com/imagekit-samples/quickstart.git

Navigate to the cloned repository and install the dependencies that are needed to run the iOS app:

cd quickstart/ios/
pod install

Once the dependencies have been installed, run the following command to open the Xcode Workspace:

open ImagekitDemo.xcodeworkspace

Select the emulator from the dropdown. Then run the app by clicking on the Run button or by pressing ⌘ + R.

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

We will be installing ImageKit iOS SDK using CocoaPods.

If you are not using CocoaPods in your project, you might need to add it to your project by either running pod init or adding PodFile (see example) in the root directory of your project.

To Install the SDK, add the following to the PodFile.

# Required to enable the use of Dynamic Libraries
use_frameworks!

target 'target_name' do 
    ...
    # Add to your project target
    pod 'ImageKitIO', '~> 3.0.0'
    ...
end

Open the AppDelegate.swift file. This is where we will initialize our SDK with the following parameters.

• urlEndpoint is the required parameter. You can get the value of the URL endpoint from your ImageKit dashboard - https://imagekit.io/dashboard/url-endpoints.
• publicKey is an optional parameter and is only needed if you want to use the SDK for client-side file upload. You can get the public key from the developer section in your ImageKit dashboard - https://imagekit.io/dashboard/developer/api-keys.

ImageKit.init(
    publicKey: "your_public_api_key", 
    urlEndpoint: "https://ik.imagekit.io/your_imagekit_id", 
    transformationPosition: TransformationPosition.PATH
)

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

To render an image using an absolute URL (full image URL), we can instantiate the ImageKitURLConstructor

let urlConstructor = ImageKit.shared.url(
    src: "https://ik.imagekit.io/demo/default-image.jpg"
)

To create a URL from the image path, we can instantiate the ImageKitURLConstructor, which takes the URL endpoint, image path, and transformation position as parameters to create the transformed url.

let urlConstructor = ImageKit.shared.url(
    urlEndpoint: "https://ik.imagekit.io/demo"
    path: "default-image.jpg",
    transformationPosition: TransformationPosition.QUERY
)

The iOS SDK provides a function for each transformation parameter, making the code simpler and readable. To add transformations, the functions can be chained with urlConstructor.

urlConstructor = urlConstructor.height(height: 400)
urlConstructor = urlConstructor.aspectRatio(width: 3, height: 2)

Finally, once all the required transformations are defined, call the create function to get the final transformed URL

let url = urlConstructor.create()
// https://ik.imagekit.io/your_imagekit_id/default-image.jpg?tr=h-400,ar-3-2

It will look like the picture below. The buttons are present in the sample app to demonstrate the use of different transformations.

This section covers the basics:‌

• ​Basic image resizing
• Crop Mode
• ​Aspect Ratio
• ​Chained transformation

ImageKit iOS SDK provides a function for each transformation parameter, e.g., height for h and width for the w parameter. It makes your code more readable. See the full list of supported transformations in iOS SDK on Github.

The complete list of transformations supported and their usage in ImageKit can be found here. If a transformation is supported in ImageKit, but a name for it cannot be found in the SDK, then use the addCustomTransformation function and pass the transformation code from ImageKit docs as the first parameter and value as the second parameter. For example - .addCustomTransformation("w", "400").

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

urlConstructor = urlConstructor.height(height: 150)
urlConstructor = urlConstructor.width(width: 400)
let url = urlConstructor.create()

Output:

Let’s now see how different crop modes 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.

urlConstructor = urlConstructor.width(width: 300)
urlConstructor = urlConstructor.height(height: 200)
urlConstructor = urlConstructor.cropMode(cropMode: CropMode.PAD_RESIZE)
let url = urlConstructor.create()

Output:

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

urlConstructor = urlConstructor.height(height: 400)
urlConstructor = urlConstructor.aspectRatio(width: 3, height: 2)
let url = urlConstructor.create()

Output:

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:

urlConstructor = urlConstructor.height(height: 400)
urlConstructor = urlConstructor.width(width: 300)
urlConstructor = urlConstructor.chainTransformation()
urlConstructor = urlConstructor.rotation(rotation: Rotation.VALUE_90)
let url = urlConstructor.create()

Output:

ImageKit.io allows you to add text and image dynamically using layers.

Text overlay can be used to superimpose text on an image. Try it like so:

urlConstructor = urlConstructor.width(width: "400")
urlConstructor = urlConstructor.raw(params: "l-text,i-Hand%20with%20a%20green%20plant,co-264120,fs-30,lx-10,ly-20,l-end")
let url = urlConstructor.create()

Output:

Image overlay can be used like this:

urlConstructor = urlConstructor.raw(params: "l-image,i-logo-white_SJwqB4Nfe.png,lx-10,ly-20,l-end")
let url = urlConstructor.create()

Output:

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

iOS SDK provides ImageKitUploader, which provides functions to allow files to be uploaded to the ImageKit media library directly from the client side.

To use upload functionality, we need to pass publicKey while initializing the SDK. Replace your_url_endpoint and your_public_key with actual values.

ImageKit.init(
    publicKey: "your_public_api_key", 
    urlEndpoint: "your_url_endpoint", 
    transformationPosition: TransformationPosition.PATH
)

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.

The tutorial repository comes with a sample backend server that we can use.

For this quick start guide, we have provided the sample implementation of the authentication endpoint using jsonwebtoken and Express. Refer this guide to create the token.

In a new terminal window, navigate to the Server folder inside the tutorial project and install its npm packages:

cd Server/
npm install

Let's modify index.js to implement http://localhost:8080/auth, which is our authenticationEndpoint.

/* 
    This is our backend server.
    Replace your_url_endpoint, your_public_key, your_private_key 
    with actual values
*/
const express = require('express');
const jwt = require('jsonwebtoken');
const app = express();
const cors = require('cors');

app.use(cors());
app.use(express.json());

const publicKey = "your_public_key";
const privateKey = "your_private_key";

app.post("/auth", function (req, res) {
  const token = jwt.sign(
    req.body.uploadPayload,
    privateKey,
    {
      expiresIn: req.body.expire,
      header: {
        alg: "HS256",
        typ: "JWT",
        kid: publicKey,
      },
    })
  res.status(200);
  res.send({ token });
});

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

Finally, run the backend app.

node index.js

You should see a log line saying that the app is “Live on port 8080”.

If you run the following command in the terminal

curl -L 'localhost:8080/auth' -H 'Content-Type: application/json' -d '{
    "uploadPayload":{
        "filename": "image.jpg",
        "folder": "/"
    },
    "expire": 60
}'

You should see a JSON response like this, which contains the JWT token. Actual values will vary.

{
    "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCIsImtpZCI6InRlc3QifQ.eyJmaWxlbmFtZSI6ImltYWdlLmpwZyIsImZvbGRlciI6Ii8iLCJpYXQiOjE3MTg2OTUwNzUsImV4cCI6MTcxODY5NTEzNX0.HN_0gHfI26drmFGHmIiZuLnz21nzz6VpTuRWUi4Ljno"
}

You can use JWT Debugger to decode and verify that the token is correctly generated.

Configure the auth endpoint in the frontend app

Head over to Constants.swift and ensure the AUTH_SERVER_API_ENDPOINT is set to http://localhost:8080/auth

To upload an image to the media library, the ImageKit iOS SDK provides ImageKitUploader . For complete API reference for the image upload function, check out the docs on the ImageKit iOS Git Repository.

The ImageKit.shared.uploader().upload function can ingest files through UIImage, NSData or Url of a remote image

ImageKit.shared.uploader().upload(
  file: image,
  token: "your_jwt_token",
  fileName: "sample-image.jpg",
  useUniqueFilename: true,
  tags: ["demo"],
  folder: "/",
  isPrivateFile: false,
  customCoordinates: "",
  responseFields: "",
  overwriteFile: false,
  overwriteAITags: false,
  overwriteTags: false,
  overwriteCustomMetadata: false,
  // Custom metadata must be defined in the Media Library before using it in the upload API
  // customMetadata: "{\"device_name\":\"iPhone 15\",\"location\":\"New York\"}",
  progress: { progress in
  	// Handle Progress
  },
  policy: UploadPolicy,
  preProcessor: UploadPreprocessor,
  completion: { result in 
  	 switch result{
            case .success(let uploadAPIResponse):
                // Handle Success Response
            case .failure(let error as UploadAPIError):
                // Handle Upload Error
            case .failure(let error):
                // Handle Other Errors
      }
  }
)

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 error log.
• Make sure that the private API key has been configured.
• The server app is running.

The UploadPolicy class represents a set of conditions that need to be met for an upload request to be executed. This policy is useful in various cases, like constraining large uploads to be performed only when the specified network and battery conditions are satisfied and controlling the retry mechanism for failed upload requests.

UploadPolicy.Builder class is responsible for building the UploadPolicy instances.

/*
 * Upload policy to upload files only 
 *  - when the network is unmetered
 *  - the device doesn't require charging
 *  - retry 4 times with exponential backoff starting at 500ms
*/

let uploadPolicy = UploadPolicy.Builder()
  .requireNetworkType(.UNMETERED)
  .requiresBatteryCharging(false)
  .maxRetries(4)
  .backoffCriteria(backoffMillis: 500, backoffPolicy: .EXPONENTIAL)
  .build()

The ImageKit iOS SDK provides a way to preprocess files before uploading them to the media library.

The ImageKitUploader can perform the preprocessing of the image/video to modify them before uploading by passing an instance of UploadPreprocessor. For complete API reference for the upload preprocessor, check out the docs

These preprocessors can be useful for certain use cases, e.g:

• Modifying the media size and/or quality to optimize the use of ImageKit storage.
• Apply certain media transformations from within the app, like when using an image editing feature.

The SDK features two built-in preprocessors:

• ImageUploadPreprocessor: This preprocessor is used to apply transformations to images before uploading them to the media library. The transformations that can be applied are:
  • Limiting width & height
  • Rotation
  • Crop
  • Format selection

let preprocessor = ImageUploadPreprocessor.Builder()
   .limit(width: 400, height: 300)
   .rotate(degrees: 45)
   .format(format: .JPEG)
   .build()

• VideoUploadPreprocessor: This preprocessor is used to apply transformations to videos before uploading them to the media library. The transformations that can be applied are:
  • Limiting width & height
  • Frame rate
  • A/V bitrate
  • Keyframes interval

let preprocessor = VideoUploadPreprocessor.Builder()
   .limit(width: 800, height: 600)
   .frameRate(frameRateValue: 60)
   .keyFramesInterval(interval: 6)
   .targetVideoBitrateKbps(targetVideoBitrateKbps: 480)
   .targetAudioBitrateKbps(targetAudioBitrateKbps: 320)
   .build(),