OC 版本：
創(chuàng)建UIImageView 分類：

xxx.m
@implementation UIImage (ImageCIr)

/** 設(shè)置圓形圖片(放到分類中使用) */
+ (nullable UIImage *)clipCircleImageWithImage:(nullable UIImage *)image circleRect:(CGRect)rect {
    //1搔耕、開(kāi)啟上下文
    UIGraphicsBeginImageContextWithOptions(image.size, NO, 0);
    
    //2隙袁、設(shè)置裁剪區(qū)域
    UIBezierPath * path = [UIBezierPath bezierPathWithOvalInRect:rect];
    [path addClip];
    
    //3、繪制圖片
    [image drawAtPoint:CGPointZero];
    
    //4弃榨、獲取新圖片
    UIImage * newImage = UIGraphicsGetImageFromCurrentImageContext();
    
    //5菩收、關(guān)閉上下文
    UIGraphicsEndImageContext();
    
    //6、返回新圖片
    return newImage;
}

xxx.h
+ (nullable UIImage *)clipCircleImageWithImage:(nullable UIImage *)image circleRect:(CGRect)rect;

使用:

UIImageView *roundImg = [[UIImageView alloc] initWithFrame:CGRectMake(0, 64, 200, 200)];
 
    UIImage *image = [UIImage imageNamed:@"zzz"];
    roundImg.image = [UIImage clipCircleImageWithImage:image circleRect:roundImg.frame];
    
    [self.view addSubview:roundImg];

Swift版本：

extension UIImageView {

   /// 圖片切成圓形
   ///
   /// - Parameters:
   ///   - image: 傳入處理的圖片
   ///   - rect: 切割的大小
   /// - Returns: 返回切割的t圓形圖片
   func clipCircleImage(with image: UIImage?, circleRect rect: CGRect) -> UIImage? {
       //1鲸睛、開(kāi)啟上下文
       UIGraphicsBeginImageContextWithOptions(image?.size ?? CGSize.zero, false, 0)
       
       //2娜饵、設(shè)置裁剪區(qū)域
       let path = UIBezierPath(ovalIn: rect)
       path.addClip()
       
       //3、繪制圖片
       image?.draw(at: CGPoint.zero)
       
       //4官辈、獲取新圖片
       let newImage: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
       
       //5箱舞、關(guān)閉上下文
       UIGraphicsEndImageContext()
       
       //6、返回新圖片
       return newImage
   }

}

調(diào)用：

let img = UIImageView.init(frame: CGRect.init(x: 0, y: 64, width: 200, height: 200))
        let customImg = UIImage.init(named: "aaa")
        
        img.image = img.clipCircleImage(with: customImg, circleRect: CGRect(x: 0, y: 0, width: img.frame.width, height: img.frame.height))
        view.addSubview(img)