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README.md

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Draw

Rectangle with border

func drawRectangle() {
    let renderer = UIGraphicsImageRenderer(size: CGSize(width: 300, height: 300))
    
    let img = renderer.image { ctx in
        let rectangle = CGRect(x: 0, y: 0, width: 300, height: 300)
        
        ctx.cgContext.setFillColor(UIColor.red.cgColor)
        ctx.cgContext.setStrokeColor(UIColor.green.cgColor)
        ctx.cgContext.setLineWidth(10)

        ctx.cgContext.addRect(rectangle)
        ctx.cgContext.drawPath(using: .fillStroke)
    }
    
    imageView.image = img
}

Rectangle with no border

func drawRectangle2() {
    let renderer = UIGraphicsImageRenderer(size: CGSize(width: 300, height: 300))
    
    let img = renderer.image { ctx in
        ctx.cgContext.setFillColor(UIColor.red.cgColor)
        ctx.cgContext.fill(CGRect(x: 0, y: 0, width: 300, height: 300))
    }
    
    imageView.image = img
}

Circle

func drawCircle() {
    let renderer = UIGraphicsImageRenderer(size: CGSize(width: 300, height: 300))
    
    let img = renderer.image { ctx in
        ctx.cgContext.setFillColor(UIColor.red.cgColor)
        ctx.cgContext.setStrokeColor(UIColor.green.cgColor)
        ctx.cgContext.setLineWidth(10)

        let rectangle = CGRect(x: 0, y: 0, width: 300, height: 300).inset(by: UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10))
        ctx.cgContext.addEllipse(in: rectangle)
        ctx.cgContext.drawPath(using: .fillStroke)
    }
    
    imageView.image = img
}
> Note: Circles need to be inset because they draw up to rectangle edge

Rotated square

func drawRotatedSquare() {
    let renderer = UIGraphicsImageRenderer(size: CGSize(width: 256, height: 256))
    
    let img = renderer.image { ctx in
        
        ctx.cgContext.translateBy(x: 128, y: 128)
        let rotations = 16
        let amount = Double.pi / Double(rotations)
        
        // add 16 rotated rectangles
        for _ in 0 ..< rotations {
            ctx.cgContext.rotate(by: CGFloat(amount))
            ctx.cgContext.addRect(CGRect(x: -64, y: -64, width: 128, height: 128))
        }
        
        ctx.cgContext.setStrokeColor(UIColor.systemRed.cgColor)
        ctx.cgContext.strokePath()
    }
    
    imageView.image = img
}

Draw lines

func drawLines() {
    let renderer = UIGraphicsImageRenderer(size: CGSize(width: 256, height: 256))
    
    let img = renderer.image { ctx in
        ctx.cgContext.translateBy(x: 128, y: 128)
        
        var first = true
        var length: CGFloat = 128
        
        for _ in 0 ..< 128 {
            ctx.cgContext.rotate(by: .pi / 2)
            if first {
                ctx.cgContext.move(to: CGPoint(x: length, y: 25))
                first = false
            } else {
                ctx.cgContext.addLine(to: CGPoint(x: length, y: 25))
            }
            
            length *= 0.99
        }
        
        ctx.cgContext.setStrokeColor(UIColor.systemRed.cgColor)
        ctx.cgContext.strokePath()
    }
    
    imageView.image = img
}

Text and images

func drawImagesAndText() {
    let renderer = UIGraphicsImageRenderer(size: CGSize(width: 256, height: 256))
    
    let img = renderer.image { ctx in
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.alignment = .center
        
        let attrs: [NSAttributedString.Key: Any] = [
            .font: UIFont.preferredFont(forTextStyle: .title1),
            .paragraphStyle: paragraphStyle
        ]
        
        let string = "The best laid schemes of mince and men"
        
        let attributedString = NSAttributedString(string: string, attributes: attrs)
        attributedString.draw(with: CGRect(x: 32, y: 32, width: 200, height: 200), options: .usesLineFragmentOrigin, context: nil)
        
        let star = UIImage(named: "star")
        star?.draw(at: CGPoint(x: 124, y: 150))
    }
    
    imageView.image = img
}

Auto Layout

import UIKit

class GraphView: UIView {
    
    let imageView = UIImageView()
    
    override init(frame: CGRect) {
        super.init(frame: .zero)
        backgroundColor = .systemYellow
        layout()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func layout() {
        imageView.translatesAutoresizingMaskIntoConstraints = false
        
        drawRectangle()
        
        addSubview(imageView)
        
        NSLayoutConstraint.activate([
            imageView.centerXAnchor.constraint(equalTo: centerXAnchor),
            imageView.centerYAnchor.constraint(equalTo: centerYAnchor),
        ])
    }

    func drawRectangle() { ... }
}

Gradient on Text

import UIKit

class ViewController: UIViewController {

    let label = GradientLabel()

    override func viewDidLoad() {
        super.viewDidLoad()
        style()
        layout()
    }

    func style() {
        label.translatesAutoresizingMaskIntoConstraints = false
        label.font = UIFont.preferredFont(forTextStyle: .title1).bold()
        label.numberOfLines = 0
        label.lineBreakMode = .byWordWrapping

        label.text = "A NEW WAY TO WORK HAS ARRIVED"

        label.gradientColors = [UIColor.blue.cgColor, UIColor.red.cgColor]
    }

    func layout() {
        view.addSubview(label)

        NSLayoutConstraint.activate([
            label.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            label.centerYAnchor.constraint(equalTo: view.centerYAnchor),
            label.widthAnchor.constraint(equalToConstant: 300)
        ])
    }
}


extension UIFont {
    func withTraits(traits: UIFontDescriptor.SymbolicTraits) -> UIFont {
        let descriptor = fontDescriptor.withSymbolicTraits(traits)
        return UIFont(descriptor: descriptor!, size: 0) //size 0 means keep the size as it is
    }
    func bold() -> UIFont {
        return withTraits(traits: .traitBold)
    }
}

class GradientLabel: UILabel {
    var gradientColors: [CGColor] = []

    override func drawText(in rect: CGRect) {
        if let gradientColor = drawGradientColor(in: rect, colors: gradientColors) {
            self.textColor = gradientColor
        }
        super.drawText(in: rect)
    }

    private func drawGradientColor(in rect: CGRect, colors: [CGColor]) -> UIColor? {
        let currentContext = UIGraphicsGetCurrentContext()
        currentContext?.saveGState()
        defer { currentContext?.restoreGState() }

        let size = rect.size
        UIGraphicsBeginImageContextWithOptions(size, false, 0)
        guard let gradient = CGGradient(colorsSpace: CGColorSpaceCreateDeviceRGB(),
                                        colors: colors as CFArray,
                                        locations: nil) else { return nil }

        let context = UIGraphicsGetCurrentContext()
        context?.drawLinearGradient(gradient,
                                    start: CGPoint.zero,
                                    end: CGPoint(x: size.width, y: 0),
                                    options: [])
        let gradientImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        guard let image = gradientImage else { return nil }
        return UIColor(patternImage: image)
    }
}

Two small circles (On/Off)

OnView.swift

import UIKit

class OnView: UIView {
    
    let size: CGFloat = 16
    let lineWidth: CGFloat = 2
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = .white
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func draw(_ rect: CGRect) {
        
        guard let context = UIGraphicsGetCurrentContext() else { return }
        
        // outer
        let outerBounds = CGRect(x: 0, y: 0, width: size, height: size).insetBy(dx: lineWidth/2, dy: lineWidth/2)

        context.setFillColor(UIColor.black.cgColor)
        context.setStrokeColor(UIColor.black.cgColor)
        context.setLineWidth(lineWidth)
        context.addEllipse(in: outerBounds)
        context.drawPath(using: .fillStroke)
        
        // inner
        let shrinkage: CGFloat = 0.6
        let innerBounds = CGRect(x: (size - size*shrinkage)/2,
                                 y: (size - size*shrinkage)/2,
                                 width: size*shrinkage,
                                 height: size*shrinkage)
        
        context.setFillColor(UIColor.black.cgColor)
        context.setStrokeColor(UIColor.white.cgColor)
        context.setLineWidth(lineWidth)
        context.addEllipse(in: innerBounds)
        context.drawPath(using: .fillStroke)
    }
    
    override var intrinsicContentSize: CGSize {
        return CGSize(width: size, height: size)
    }
}

OffView.swift

import Foundation
import UIKit

class OffView: UIView {
    
    let size: CGFloat = 16
    let lineWidth: CGFloat = 2
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = .white
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func draw(_ rect: CGRect) {
        
        guard let context = UIGraphicsGetCurrentContext() else { return }
        
        let rectangle2 = CGRect(x: 0, y: 0, width: size, height: size).insetBy(dx: lineWidth/2, dy: lineWidth/2)
        
        context.setFillColor(UIColor.white.cgColor)
        context.setStrokeColor(UIColor.black.cgColor)
        context.setLineWidth(lineWidth)
        context.addEllipse(in: rectangle2)
        context.drawPath(using: .fillStroke)
    }
    
    override var intrinsicContentSize: CGSize {
        return CGSize(width: size, height: size)
    }
}

Links that help