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

@property (nonatomic, weak) UIView *clipView;

- (UIView *)clipView{  //如果clipView為被創(chuàng)建，就創(chuàng)建  if (_clipView == nil)  {    UIView *view = [[UIView alloc] init];    _clipView = view;    //設置clipView的背景色和透明度    view.backgroundColor = [UIColor blackColor];    view.alpha = 0.5;    //將clipView添加到控制器的view上，此時的clipView不會顯示（未設置其frame）    [self.view addSubview:_clipView];  }  return _clipView;}

/**創(chuàng)建手勢**/UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];  /**  *每當pan手勢的位置發(fā)生變化，就會調(diào)用pan:方法，并將手勢作為參數(shù)傳遞  *//**添加手勢**/[self.view addGestureRecognizer:pan];

@property (nonatomic, assign) CGPoint startPoint;

- (void)pan:(UIPanGestureRecognizer *)pan{  CGPoint endPoint = CGPointZero;  if (pan.state == UIGestureRecognizerStateBegan)  {    /**開始點擊時，記錄手勢的起點**/    self.startPoint = [pan locationInView:self.view];  }  else if(pan.state == UIGestureRecognizerStateChanged)  {    /**當手勢移動時，動態(tài)改變終點的值，并計算起點與終點之間的矩形區(qū)域**/    endPoint = [pan locationInView:self.view];    //計算矩形區(qū)域的寬高    CGFloat w = endPoint.x - self.startPoint.x;    CGFloat h = endPoint.y - self.startPoint.y;    //計算矩形區(qū)域的frame    CGRect clipRect = CGRectMake(self.startPoint.x, self.startPoint.y, w, h);    //設置剪切區(qū)域的frame    self.clipView.frame = clipRect;  }  else if(pan.state == UIGestureRecognizerStateEnded)  {    /**若手勢停止，將剪切區(qū)域的圖片內(nèi)容繪制到圖形上下文中**/    //開啟位圖上下文    UIGraphicsBeginImageContextWithOptions(self.imageView.bounds.size, NO, 0);    //創(chuàng)建大小等于剪切區(qū)域大小的封閉路徑    UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.clipView.frame];    //設置超出的內(nèi)容不顯示，    [path addClip];    //獲取繪圖上下文    CGContextRef context = UIGraphicsGetCurrentContext();    //將圖片渲染的上下文中    [self.imageView.layer renderInContext:context];    //獲取上下文中的圖片    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();    //關閉位圖上下文    UIGraphicsEndImageContext();    //移除剪切區(qū)域視圖控件，并清空    [self.clipView removeFromSuperview];    self.clipView = nil;    //將圖片顯示到imageView上    self.imageView.image = image;    //通過alertView提示用戶，是否將圖片保存至相冊    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"保存圖片" message:@"是否將圖片保存至相冊？" delegate:self cancelButtonTitle:@"否" otherButtonTitles:@"是", nil];    [alertView show];}}

- (void)alertView:(nonnull UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{  //若點擊了“是”，則保存圖片  if (buttonIndex == 1)  {    UIImageWriteToSavedPhotosAlbum(self.imageView.image, nil, nil, nil);    /**    * 該方法可以設置保存完畢調(diào)用的方法，此處未進行設置    */  }}