NEW: Learn SwiftUI with my free YouTube video series! >>

< Previous: Transforms and lines   Next: Wrap up >

Images and text

Add one final case to your switch/case statement calling a method drawImagesAndText(), because no discussion of Core Graphics would be useful without telling you how to draw images and text to your context.

If you have an attributed string in Swift, how can you place it into a graphic? The answer is simpler than you think: attributed strings have a built-in method called draw(with:) that draws the string in a rectangle you specify. Even better, your attributed string styles are used to customize the font and size, the formatting, the line wrapping and more all with that one method.

Remarkably, the same is true of UIImage: any image can be drawn straight to a context, and it will even take into account the coordinate reversal of Core Graphics.

To help make the code clearer, here's a bulleted list of all the things the method needs to do:

  1. Create a renderer at the correct size.
  2. Define a paragraph style that aligns text to the center.
  3. Create an attributes dictionary containing that paragraph style, and also a font.
  4. Wrap that attributes dictionary and a string into an instance of NSAttributedString.
  5. Load an image from the project and draw it to the context.
  6. Update the image view with the finished result.

Below is that the same process, now coded in Swift. As per usual, the number comments match the list above:

func drawImagesAndText() {
    // 1
    let renderer = UIGraphicsImageRenderer(size: CGSize(width: 512, height: 512))

    let img = renderer.image { ctx in
        // 2
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.alignment = .center

        // 3
        let attrs: [NSAttributedString.Key: Any] = [
            .font: UIFont.systemFont(ofSize: 36),
            .paragraphStyle: paragraphStyle

        // 4
        let string = "The best-laid schemes o'\nmice an' men gang aft agley"
        let attributedString = NSAttributedString(string: string, attributes: attrs)

        // 5
        attributedString.draw(with: CGRect(x: 32, y: 32, width: 448, height: 448), options: .usesLineFragmentOrigin, context: nil)

        // 5
        let mouse = UIImage(named: "mouse")
        mouse?.draw(at: CGPoint(x: 300, y: 150))

    // 6
    imageView.image = img

That completes our project – good job!

Strings and UIImages have built-in methods that let you draw them to a Core Graphics context.

SPONSOR Meet the new Instabug – more than just bug reporting! We help you build better apps and minimize your debugging time. With each bug report, we automatically capture details like network requests, repro steps, and session details. Get real-time crash reports with stack trace details and session data to help you catch and fix issues easily. And with our customizable in-app surveys, you’ll gather insightful user feedback and much more. Instabug is the fastest and easiest way to release with confidence. Start your free trial now! Start your free trial now!

< Previous: Transforms and lines   Next: Wrap up >
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Average rating: 4.8/5

Click here to visit the Hacking with Swift store >>