Core Graphics is a powerful framework provided by Apple that allows developers to create 2D graphics, handle images, and perform drawing operations. This framework is a part of the Core Graphics framework (also known as Quartz), which is essential for rendering graphics in iOS and macOS applications. In this article, we will explore how to create custom graphics using Core Graphics in Swift, providing practical examples and sample code to illustrate the process.

Introduction to Core Graphics

Core Graphics provides a low-level, lightweight 2D rendering API that is highly efficient and flexible. It is used for drawing shapes, text, images, and more. Core Graphics is integrated into the UIKit and AppKit frameworks, making it an essential tool for iOS and macOS developers.

Setting Up Your Project

To start using Core Graphics in your Swift project, you need to import the Core Graphics framework. Here’s how you can set up a basic project:

1. Open Xcode and create a new project.
2. Choose "App" under the iOS or macOS section.
3. Name your project and ensure the language is set to Swift.
4. Import the Core Graphics framework in your Swift file:

import CoreGraphics
import UIKit // For iOS development
// import AppKit // For macOS development

Drawing Custom Shapes

Let's create a custom UIView subclass to draw a simple rectangle and a circle using Core Graphics.

import UIKit

class CustomView: UIView {
    override func draw(_ rect: CGRect) {
        super.draw(rect)

        guard let context = UIGraphicsGetCurrentContext() else { return }

        // Drawing a rectangle
        context.setFillColor(UIColor.blue.cgColor)
        context.fill(CGRect(x: 50, y: 50, width: 100, height: 100))

        // Drawing a circle
        context.setFillColor(UIColor.red.cgColor)
        context.fillEllipse(in: CGRect(x: 200, y: 50, width: 100, height: 100))
    }
}

In this example, we override the draw(_:) method of UIView to perform custom drawing. We use the UIGraphicsGetCurrentContext() function to get the current graphics context and then use this context to draw a rectangle and a circle.

Drawing Text

Core Graphics also allows you to draw text. Here’s how you can draw text within a custom view:

import UIKit

class CustomTextView: UIView {
    override func draw(_ rect: CGRect) {
        super.draw(rect)

        guard let context = UIGraphicsGetCurrentContext() else { return }

        let text = "Hello, Core Graphics!"
        let attributes: [NSAttributedString.Key: Any] = [
            .font: UIFont.systemFont(ofSize: 24),
            .foregroundColor: UIColor.black
        ]

        let attributedString = NSAttributedString(string: text, attributes: attributes)
        attributedString.draw(at: CGPoint(x: 50, y: 200))
    }
}

In this example, we create an NSAttributedString with specific attributes and draw it at a specified point using the draw(at:) method.

Handling Images

Core Graphics provides robust support for image manipulation. Here’s an example of how to draw an image in a custom view:

import UIKit

class CustomImageView: UIView {
    override func draw(_ rect: CGRect) {
        super.draw(rect)

        guard let context = UIGraphicsGetCurrentContext() else { return }

        if let image = UIImage(named: "example.png")?.cgImage {
            context.draw(image, in: CGRect(x: 50, y: 300, width: 100, height: 100))
        }
    }
}

In this example, we load an image from the app bundle and draw it within the view using the context.draw(_:in:) method.

Conclusion

Core Graphics is a versatile and powerful framework for creating custom graphics in iOS and macOS applications. By understanding the basics of drawing shapes, text, and images, you can create rich and engaging user interfaces. The examples provided in this article should give you a solid foundation to start exploring Core Graphics in your own projects.