// 创建一个view
 UIView *showView = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
 [self.view addSubview:showView];
 showView.backgroundColor = [UIColor whiteColor];
 showView.alpha = 0.5;
 
 // 贝塞尔曲线(创建一个圆)
 UIBezierPath *path = [UIBezierPath  bezierPathWithArcCenter:CGPointMake(100 / 2.f, 100 / 2.f)
              radius:100 / 2.f
              startAngle:0 
              endAngle:M_PI * 2
              clockwise:YES];
 
  CAShapeLayer *layer = [CAShapeLayer layer];
  layer.frame = showView.bounds;
  layer.path = path.CGPath;
  [showView.layer addSublayer:layer];

 - (UIImageView *)avatarImage { 

  if (!_avatarImage) { 
  
  _avatarImage = [[UIImageView alloc] initWithFrame:CGRectMake(20,10, avatarDiameter, avatarDiameter)];
  _avatarImage.backgroundColor = [UIColor grayColor];
  _avatarImage.contentMode = UIViewContentModeScaleAspectFit;
  _avatarImage.layer.cornerRadius = avatarDiameter/2.0;
  _avatarImage.layer.masksToBounds = YES;
  [_avatarImage setImage:[UIImage imageNamed:@"test.jpg"]];
  }
 return _avatarImage;
}

- (instancetype)initWithFrame:(CGRect)frame {
 
 if (self = [super initWithFrame:frame]) {
  
 }
 return self;
}
- (void)drawRect:(CGRect)rect { 
  // Drawing code 
 CGRect bounds = self.bounds;
 [[UIColor whiteColor] set];
 UIRectFill(bounds);

 [[UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:CGRectGetWidth(bounds)/2.0] addClip];
 [self.image drawInRect:bounds];
} 

- (instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {
 
  if (self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]) {
  
   [self.contentView addSubview:self.avatarImage];
   [self.contentView addSubview:self.maskImage];
  }
  return self;
 }

- (UIImageView *)avatarImage {
 
  if (!_avatarImage) { 
  
  _avatarImage = [[UIImageView alloc] initWithFrame:CGRectMake(20,10, avatarDiameter, avatarDiameter)];
  _avatarImage.backgroundColor = [UIColor grayColor];
  _avatarImage.contentMode = UIViewContentModeScaleAspectFit;
   [_avatarImage setImage:[UIImage imageNamed:@"test.jpg"]];
  }
  return _avatarImage;
 }

 //中心镂空的图
 - (UIImageView *)maskImage { 
 
  if (!_maskImage) { 
  
  _maskImage = [[UIImageView alloc] initWithFrame:CGRectMake(20,10, avatarDiameter, avatarDiameter)]; 
  _maskImage.contentMode = UIViewContentModeScaleAspectFit; 
  [_maskImage setImage:[UIImage imageNamed:@"corner_circle.png"]]; 
  }
  return _maskImage;
}