iOS 图片截取

关于图片截取效果
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思路：
1、获取手指触屏的一个点
2、随着手指触屏的移动矩形大小随之变化
3、手指离开的时候绘制图片
4、创建当前矩形的上下文
5、确定裁剪范围
6、获取图片
7、关闭上下文

代码：

@interface DrawPictureVC ()@property (weak, nonatomic) IBOutlet UIView *backView;@property (weak, nonatomic) IBOutlet UIImageView *imageView;@property (nonatomic,strong) UIView *clipView;@property (nonatomic,assign) CGPoint startP;@end@implementation DrawPictureVC- (void)viewDidLoad {    [super viewDidLoad];    self.title = @"draw Picture";    //给view添加一个是手势    UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc]init];    [panGesture addTarget:self action:@selector(pan:)];    [self.backView addGestureRecognizer:panGesture];}-(UIView *)clipView{    if (_clipView == nil) {        _clipView = [[UIView alloc]init];        [_clipView setBackgroundColor:[UIColor grayColor]];        [_clipView setAlpha:0.5];        [self.backView addSubview:_clipView];    }    return _clipView;}-(void)pan:(UIPanGestureRecognizer *)pan{    CGPoint endP = CGPointZero;    if (pan.state == UIGestureRecognizerStateBegan){        //开始拖动的时候，获取开始点        self.startP = [pan locationInView:self.backView];    }else if (pan.state == UIGestureRecognizerStateChanged){        //一直处于拖动的时候，获取变化点        endP = [pan locationInView:self.backView];        CGFloat w = endP.x - self.startP.x;        CGFloat h = endP.y - self.startP.y;        //生成矩形变化范围        [self.clipView setFrame:CGRectMake(self.startP.x, self.startP.y, w, h)];    }else if (pan.state == UIGestureRecognizerStateEnded){        //停止拖动的时候        //创建位图上下文        UIGraphicsBeginImageContextWithOptions(self.backView.bounds.size, NO, 0);        //设置裁剪区域        UIBezierPath *backPath = [UIBezierPath bezierPathWithRect:self.clipView.frame];        [backPath addClip];        //获取当前上下文        CGContextRef ctx = UIGraphicsGetCurrentContext();        //把控件上的内容渲染到上下文        [self.imageView.layer renderInContext:ctx];        //获取图片        self.imageView.image = UIGraphicsGetImageFromCurrentImageContext();       //关闭上下文        UIGraphicsEndImageContext();        //移除置nil        [self.clipView removeFromSuperview];        self.clipView = nil;    }}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end

最后，附上相关的demo,Git：(https://github.com/hejiasu/Drawing)