UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
//只需要设置layer层的两个属性
//设置圆角
imageView.layer.cornerRadius = imageView.frame.size.width / 2;
//将多余的部分切掉
imageView.layer.masksToBounds = YES;
[self.view addSubview:imageView];

UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
 imageView.image = [UIImage imageNamed:@"1"];
 //开始对imageView进行画图
 UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, NO, 1.0);
 //使用贝塞尔曲线画出一个圆形图
 [[UIBezierPath bezierPathWithRoundedRect:imageView.bounds cornerRadius:imageView.frame.size.width] addClip];
 [imageView drawRect:imageView.bounds];
 imageView.image = UIGraphicsGetImageFromCurrentImageContext();
 //结束画图
 UIGraphicsEndImageContext();
 [self.view addSubview:imageView];

#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>
@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
  
  [super viewDidLoad];
  
  UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 200, 100)];
  imageView.image = [UIImage imageNamed:@"1"];
  UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:imageView.bounds byRoundingCorners:UIRectCornerBottomLeft | UIRectCornerTopLeft cornerRadii:CGSizeMake(25, 5)];
  CAShapeLayer *maskLayer = [[CAShapeLayer alloc]init];
  maskLayer.frame = imageView.bounds;
  maskLayer.path = maskPath.CGPath;
  imageView.layer.mask = maskLayer;
  [self.view addSubview:imageView];
}