MyImageView

#import "MyImageView.h"

@implementation MyImageView


// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.

/** uiimageview这个类不会自动画线    image更改显示不出 要在控制器里写*/
//- (void)drawRect:(CGRect)rect {
//    // Drawing code
//    UIBezierPath *path = [UIBezierPath bezierPath];
//    [path moveToPoint:CGPointMake(50, 50)];
//    [path addLineToPoint:CGPointMake(100, 100)];
//    path.lineWidth = 20;
//    [path stroke];
//    
//    
//}


@end

MyView.h

#import <UIKit/UIKit.h>
typedef void (^PathBlock)(UIBezierPath *p);
@interface MyView : UIView
@property(nonatomic,copy)PathBlock pb;
@end

MyView.m

#import "MyView.h"

@interface MyView ()

@property(nonatomic,strong)NSMutableArray *pathArray;
@end
@implementation MyView
/** 懒加载pathArray */
- (NSMutableArray *)pathArray{
    if (!_pathArray) {
        _pathArray = [NSMutableArray array];
    }
    return _pathArray;
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    // 1. 获取起始点 并且创建路径
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:[[touches anyObject] locationInView:self]];
    // 2. 装入数组
    [self.pathArray addObject:path];
    
}
-(void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    // 1. 获取终点 (不止一个)
    UIBezierPath *path = [self.pathArray lastObject];
    [path addLineToPoint:[[touches anyObject] locationInView:self]];
    // 2. 调用drawRect(drawrect不会自动调用 需要使用以下方法)
    [self setNeedsDisplay];
 
}
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
   // 封闭路径
    UIBezierPath *path = [self.pathArray lastObject];
    [path closePath];

    [self setNeedsDisplay];
    //调用block传递路径
   self.pb(path);
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
    for (UIBezierPath *path in self.pathArray) {
        path.lineWidth = 2;
        [path stroke];
    }
}


@end

ViewController.m

#import "ViewController.h"
#import "MyImageView.h"
#import "MyView.h"
@interface ViewController ()
@property(nonatomic,strong)UIImageView *imageView;
@property(nonatomic,strong)MyView *mv;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
// 获取图片
   __block UIImage *image = [UIImage imageNamed:@"1.png"];
    
    self.imageView = [[UIImageView alloc]initWithImage:image];
    [self.view addSubview:self.imageView];
    self.mv = [[MyView alloc]initWithFrame:self.imageView.frame];
    self.mv.backgroundColor = [UIColor colorWithRed:1 green:1 blue:1 alpha:0]; //这种透明方式 不会让子视图也变透明(alpha是直接设置会让子视图也透明)
    [self.view addSubview:self.mv
     ];
    //剪切
    __weak typeof(self) weakSelf = self;
    self.mv.pb = ^(UIBezierPath *p){
    
        //获取上下文
        UIGraphicsBeginImageContextWithOptions(image.size, NO, 0);
        //剪切路径
        UIBezierPath *path = p;
        //剪切
        [path addClip];
        //绘制
        [image drawAtPoint:CGPointZero];
        // 4 .需要接收剪切之后的图
        image = UIGraphicsGetImageFromCurrentImageContext();
        // 5. 关闭上下文
        UIGraphicsEndImageContext();
        //显示出来剪切的图
        weakSelf.imageView.image = image;
    
        
        
    };
}



/******** 剪切一张图 ************/
- (void)clipImage{

    // 1. 拥有一张图
    UIImage *image = [UIImage imageNamed:@"1.png"];
    MyImageView *myImageView = [[MyImageView alloc]initWithImage:image];
    
    CGRect rect = CGRectMake(50, 50, 0, 0);
    rect.size = image.size;
    myImageView.frame = rect;
    //以上是剪切之前的图片显示
    //获取上下文
    UIGraphicsBeginImageContextWithOptions(image.size, NO, 0);
    // 2. 需要剪裁的范围
    //    UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(10, 10, 50, 50)];
    //剪切个圆
    UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
    // 3. 剪切 原来的图不变
    [path addClip];
    //绘制
    [image drawAtPoint:CGPointZero];
    // 4 .需要接收剪切之后的图
    UIImage *clipImage = UIGraphicsGetImageFromCurrentImageContext();
    // 5. 关闭上下文
    UIGraphicsEndImageContext();
    //显示出来剪切的图
    myImageView.image = clipImage;
        
    [self.view addSubview:myImageView];
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end