UIImage+roundCorner.swift

public extension UIImage {
    /// 圆角图片
    func roundCornerImage(withCornerRadius cornerRadius: CGFloat) -> UIImage? {
        // 开关图形上下文
        UIGraphicsBeginImageContext(size)
        defer { UIGraphicsEndImageContext() }
        // 获取图形上下文
        let context = UIGraphicsGetCurrentContext()
        // 带圆角的长方形贝塞尔曲线
        let roundedRect = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        let path = UIBezierPath(roundedRect: roundedRect, cornerRadius: cornerRadius)
        // 在图形上下文中添加贝塞尔曲线
        context?.addPath(path.cgPath)
        // 在上下文中沿贝塞尔曲线切出圆角
        context?.clip()
        // 将图片画在上下文中
        draw(in: roundedRect)
        // 最后返回上下文中图片
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}