UIImage extension for generating two-letter avatars with reproducible color.

UIImage+Avatar, UIFont+Traits

import Foundation
import UIKit

extension UIFont {
    func with(traits: UIFontDescriptor.SymbolicTraits) -> UIFont {
        if let fontDescriptor = self.fontDescriptor.withSymbolicTraits(traits) {
            return UIFont(descriptor: fontDescriptor, size: 0)
        } else {
            return self
        }
    }
    
    func with(weight: UIFont.Weight) -> UIFont {
        let fontDescriptor = self.fontDescriptor.addingAttributes([
            .traits: [
                UIFontDescriptor.TraitKey.weight: weight,
            ],
        ])
        return UIFont(descriptor: fontDescriptor, size: 0)
    }
}

UIImage+Avatar.swift

import Foundation
import UIKit

extension UIImage {
    class func avatar(
        id:          Int = 0,
        text:        String?,
        size:        CGSize,
        saturation:  CGFloat = 0.40,
        brightness:  CGFloat = 0.80,
        font:        UIFont? = nil,
        corners:     CGFloat = 0,
        placeholder: UIImage?
    ) -> UIImage? {
        // есть текст?
        guard let text = text, text.isEmpty == false else {
            return placeholder
        }
        
        // вычислим инициалы
        let words: [String] = text.components(separatedBy: CharacterSet.whitespacesAndNewlines.union(.punctuationCharacters))
        let first: [String] = words.compactMap({ $0.first }).map(String.init)
        
        let initials = { () -> String in
            switch first.count {
            case 2...: return first[0] + first[1]
            case 1:    return String(first[0].prefix(2))
            default:   return ""
            }
        }().uppercased()
        
        // пусто?
        guard initials.isEmpty == false else {
            return placeholder
        }
        
        // хэш
        let hash: UInt = UInt(bitPattern: (String(id) + initials).hashValue)
        
        // оттенок
        let hue = CGFloat(hash % 360) / 360
        
        // цвета
        let backgroundColor =
            UIColor(
                hue: hue,
                saturation: saturation,
                brightness: brightness,
                alpha: 1
            )
        
        let textColor =
            UIColor(
                hue: 0,
                saturation: 0,
                brightness: brightness > 0.8 ? 0.2 : 1.0,
                alpha: 1
            )
        
        // шрифт
        let font: UIFont = font ?? UIFont.systemFont(ofSize: floor(size.height / 2), weight: .regular).with(traits: .traitCondensed)
        
        // нарисуем и отдадим картинку
        return UIGraphicsImageRenderer(size: size).image { context in
            // фон
            backgroundColor.setFill()
            UIBezierPath(roundedRect: CGRect(origin: .zero, size: size), cornerRadius: corners).fill()
            
            // текст
            let attributedText = NSAttributedString(string: initials, attributes: [
                .font: font,
                .foregroundColor: textColor,
            ])
            let options: NSStringDrawingOptions = [.usesLineFragmentOrigin]
            let textSize = attributedText.boundingRect(with: .zero, options: options, context: nil).size
            let textRect = CGRect(x: (size.width - textSize.width) / 2, y: (size.height - textSize.height) / 2, width: textSize.width, height: textSize.height)
            
            attributedText.draw(with: textRect, options: options, context: nil)
        }
    }
}