在image上切一个透明的圆

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@property(nonatomic ,strong)NSArray *hollowFrames;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self addShadowView];
}
- (void)addShadowView {
    self.hollowFrames = @[[NSValue valueWithCGPoint:CGPointMake(20.0, 20.0)], [NSValue valueWithCGPoint:CGPointMake(120.0, 20.0)]];
    
    int radius = 15.0;
    UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height) cornerRadius:0];
    
    for (NSValue *point in self.hollowFrames) {
        UIBezierPath *circlePath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(point.CGPointValue.x, point.CGPointValue.y, 2.0*radius, 2.0*radius) cornerRadius:radius];
        [path appendPath:circlePath];
    }
    
    [path setUsesEvenOddFillRule:YES];
    
    CAShapeLayer *fillLayer = [CAShapeLayer layer];
    fillLayer.path = path.CGPath;
    fillLayer.fillRule = kCAFillRuleEvenOdd;
    fillLayer.fillColor = [UIColor blackColor].CGColor;
    fillLayer.opacity = 0.5;
    [self.imageView.layer addSublayer:fillLayer];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


@end