截屏

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, weak) UIView *cover;

@property (nonatomic, assign) CGPoint oriP;

@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@property (weak, nonatomic) IBOutlet UIView *view1;

@end

@implementation ViewController
//- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
//{
//    CGRect frame = _view1.frame;
////    frame.size.width = -100;
////    _view1.frame = frame;
////}
- (UIView *)cover
{
    if (_cover == nil) {
        UIView *view = [[UIView alloc] init];
        
        
        view.backgroundColor = [UIColor blackColor];
        view.alpha = 0.5;
        
        _cover = view;
        
        [self.view addSubview:view];
        
    }
    return _cover;
}

- (IBAction)pan:(UIPanGestureRecognizer *)sender {
    // 获取下当前的触摸
    CGPoint curP = [sender locationInView:_imageView];
    if (sender.state == UIGestureRecognizerStateBegan) {
        // 记录下一开始的位置
        _oriP = curP;
    }
    
    // 计算下黑色蒙版的frame
    CGFloat w = curP.x - _oriP.x;
    CGFloat h = curP.y - _oriP.y;
    
    self.cover.frame = CGRectMake(_oriP.x, _oriP.y, w, h);

    
    if (sender.state == UIGestureRecognizerStateEnded) { // 手指抬起
        
        // 裁剪图片,生成一张新图片
        
        // 开启位图上下文
        UIGraphicsBeginImageContextWithOptions(_imageView.bounds.size, NO, 0);
        
        // 设置裁剪区域
        UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.cover.frame];
        [path addClip];
        
        
        // 绘制图片
        [_imageView.layer renderInContext:UIGraphicsGetCurrentContext()];
        
        // 生成图片
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        
        // 关闭上下文
        UIGraphicsEndImageContext();
        
        _imageView.image = image;
        
        [self.cover removeFromSuperview];
        
        
    }
    
    
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    // 创建拖动手势
//    UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
//    
//    [_imageView addGestureRecognizer:pan];
}

//- (void)pan:(UIPanGestureRecognizer *)pan
//{
//    NSLog(@"%s",__func__);
//}


@end