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iOS development
Swift programming
image editing
text overlay
app development

How do I add text to an image in iOS Swift?

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Introduction

To add text to an image in Swift, the standard approach is to draw the original image and the text into a new graphics context, then return the rendered result as a UIImage. That gives you a new image with the text permanently baked into the pixels. If you only need a caption on screen, an overlay UILabel is often a better design than modifying the image itself.

Draw Into a New Image

UIGraphicsImageRenderer is the clean UIKit API for this job.

swift
1import UIKit
2
3func imageByAddingText(_ text: String, to image: UIImage) -> UIImage {
4    let renderer = UIGraphicsImageRenderer(size: image.size)
5
6    return renderer.image { _ in
7        image.draw(in: CGRect(origin: .zero, size: image.size))
8
9        let attributes: [NSAttributedString.Key: Any] = [
10            .font: UIFont.boldSystemFont(ofSize: 32),
11            .foregroundColor: UIColor.white
12        ]
13
14        text.draw(at: CGPoint(x: 20, y: 20), withAttributes: attributes)
15    }
16}

This creates a brand-new UIImage. The original image remains unchanged.

Measure Before Positioning

Hardcoded coordinates are fine for a quick demo, but real apps usually need placement that adapts to image size and text length.

swift
1import UIKit
2
3func watermarkedImage(text: String, image: UIImage) -> UIImage {
4    let renderer = UIGraphicsImageRenderer(size: image.size)
5
6    return renderer.image { _ in
7        image.draw(in: CGRect(origin: .zero, size: image.size))
8
9        let attributes: [NSAttributedString.Key: Any] = [
10            .font: UIFont.systemFont(ofSize: 28, weight: .semibold),
11            .foregroundColor: UIColor.white,
12            .backgroundColor: UIColor.black.withAlphaComponent(0.35)
13        ]
14
15        let textSize = text.size(withAttributes: attributes)
16        let origin = CGPoint(
17            x: image.size.width - textSize.width - 20,
18            y: image.size.height - textSize.height - 20
19        )
20
21        text.draw(at: origin, withAttributes: attributes)
22    }
23}

This pattern works well for captions and watermarks in the lower-right corner.

Use Attributed Text for Better Styling

If you need richer typography, use NSAttributedString.

swift
1import UIKit
2
3func imageWithStyledText(image: UIImage) -> UIImage {
4    let renderer = UIGraphicsImageRenderer(size: image.size)
5
6    return renderer.image { _ in
7        image.draw(at: .zero)
8
9        let text = NSAttributedString(
10            string: "Hello iOS",
11            attributes: [
12                .font: UIFont.italicSystemFont(ofSize: 30),
13                .foregroundColor: UIColor.yellow,
14                .strokeColor: UIColor.black,
15                .strokeWidth: -2
16            ]
17        )
18
19        text.draw(at: CGPoint(x: 24, y: 24))
20    }
21}

That gives you control over color, font, stroke, paragraph style, and other formatting details.

Overlaying Text in the UI Is a Different Problem

Sometimes developers say they want to add text to an image, but they really want text displayed on top of an image view. In that case, do not redraw the image at all.

swift
1import UIKit
2
3let imageView = UIImageView(image: UIImage(named: "photo"))
4let label = UILabel(frame: CGRect(x: 20, y: 20, width: 120, height: 32))
5label.text = "Preview"
6label.textColor = .white
7label.backgroundColor = UIColor.black.withAlphaComponent(0.5)
8
9imageView.addSubview(label)

This keeps the text editable and avoids generating a new bitmap every time the caption changes.

A Reusable UIImage Extension

If the operation appears often in your codebase, a UIImage extension keeps the call site clean.

swift
1import UIKit
2
3extension UIImage {
4    func adding(text: String) -> UIImage {
5        let renderer = UIGraphicsImageRenderer(size: size)
6        return renderer.image { _ in
7            draw(at: .zero)
8            text.draw(at: CGPoint(x: 16, y: 16), withAttributes: [
9                .font: UIFont.systemFont(ofSize: 24),
10                .foregroundColor: UIColor.white
11            ])
12        }
13    }
14}

Then use it like this:

swift
let output = inputImage.adding(text: "Sample")

Think About Scale and Contrast

Images with very high resolution can make a fixed font size look tiny. Busy photos can also make white text unreadable. A semitransparent background, shadow, or stroke is often necessary if the text must remain legible across different images.

Common Pitfalls

  • Baking text into the image when a simple UI overlay would have been more flexible.
  • Hardcoding positions without measuring the rendered text first.
  • Ignoring image size and scale, which makes the text look too small or too large.
  • Choosing colors that disappear against the photo background.
  • Reaching for older graphics APIs when UIGraphicsImageRenderer is the clearer modern UIKit option.

Summary

  • To permanently add text, draw the image and text into a new graphics context.
  • 'UIGraphicsImageRenderer is the standard UIKit tool for this work.'
  • Measure the text before positioning it if placement must adapt to different images.
  • Use attributed text when you need richer styling.
  • If the text is only for display, overlay a label instead of modifying the image pixels.
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