使用Core Graphics在UIImageView上绘制矩形

import UIKit

class CustomDrawingView: UIView {
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        
        // 获取当前绘图上下文
        guard let context = UIGraphicsGetCurrentContext() else { return }
        
        // 设置矩形的填充颜色
        context.setFillColor(UIColor.red.cgColor)
        
        // 创建矩形的绘制区域
        let rectangleRect = CGRect(x: 50, y: 50, width: 200, height: 100)
        
        // 在绘图上下文中绘制矩形
        context.fill(rectangleRect)
    }
}

// 在UIImageView上添加自定义的绘图视图
let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 300, height: 200))
let customView = CustomDrawingView(frame: imageView.bounds)
imageView.addSubview(customView)