BLACK FRIDAY: Save 50% on all my Swift books and bundles! >>

How to use Core Image filters the type-safe way

iOS 13 fixed this once and for all

Paul Hudson       @twostraws

iOS 13 introduced new type-safe initializers for Core Image filters that allow us to use them much more easily – and without having to hope that our code works at runtime. Previously much of Core Image was stringly typed, meaning that we would create filters using strings, which in turn meant that Swift couldn't be sure that when we asked for a value to be set that it would actually exist. iOS 13 replaces that with a much better implementation, and you'll never want to go back to the old way.

This functionality is enabled by new protocols that define exactly what each filter can do. For example, CILinearGradient has two points and two colors, while CIBarsSwipeTransition has an angle, a width, and a bar offset. So, while we aren't getting concrete types back, the protocols at least mean we have guaranteed access to all the properties we need.

Start by adding an import to bring in all the new types:

import CoreImage
import CoreImage.CIFilterBuiltins

Now you can go ahead and create filters using static methods on CIFilter. For example, CIFilter.qrCodeGenerator() sends back a filter to generate QR codes. Once you have the type you want, you'll find properties you can set specific to that filter, which is a huge improvement over the old calls to setValue(_forKey:).

For example, we could we create a Gaussian blur effect using CIFilter.gaussianBlur(), set its input image and radius, then read out the result:

let context = CIContext(options: nil)
let blur = CIFilter.gaussianBlur()
blur.inputImage = CIImage(image: exampleImage)
blur.radius = 30

if let output = blur.outputImage {
    if let cgimg = context.createCGImage(output, from: output.extent) {
        let processedImage = UIImage(cgImage: cgimg)
        // use your blurred image here
    }
}
Save 50% in my WWDC sale.

SAVE 50% All our books and bundles are half price for Black Friday, so you can take your Swift knowledge further without spending big! Get the Swift Power Pack to build your iOS career faster, get the Swift Platform Pack to builds apps for macOS, watchOS, and beyond, or get the Swift Plus Pack to learn advanced design patterns, testing skills, and more.

Save 50% on all our books and bundles!

BUY OUR BOOKS
Buy Pro Swift Buy Pro SwiftUI Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let us know!

Average rating: 4.5/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.