79-图片擦除(纯代码)

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// ViewController.m
// 图片擦除(纯代码)

// 如果想要要通过storyboard拖拽方式操作，拖两个imageview

// 其中用于做擦除操作的要连线，并给其拖一个手指移动的手势
#import "ViewController.h"

@interface ViewController ()
//保存用于做擦除操作的图片
@property (nonatomic,weak) UIImageView *imageView;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //1.创建两个imageview

    //用于显示擦除后的图片
    UIImageView *imageView1=[[UIImageView alloc] init];
    imageView1.image=[UIImage imageNamed:@"2B"];
    //设置ImageView可以和用户交互
    imageView1.userInteractionEnabled=NO;
    imageView1.frame=self.view.bounds;
    [self.view addSubview:imageView1];

    //用于做擦除操作的图片
    UIImageView *imageView2=[[UIImageView alloc] init];
    imageView2.image=[UIImage imageNamed:@"2A"];
    imageView2.frame=self.view.bounds;
    imageView2.userInteractionEnabled=YES;
    _imageView=imageView2;
    [self.view addSubview:imageView2];

    //2.给用于做擦除操作的imageView添加手指移动手势
    UIPanGestureRecognizer *pan=[[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
    [_imageView addGestureRecognizer:pan];
}

//3.监听手指移动事件
-(void) pan:(UIPanGestureRecognizer *)pan
{
    //获取当前手指位置
    CGPoint curP=[pan locationInView:_imageView];

    //开启位图上下文
    UIGraphicsBeginImageContextWithOptions(_imageView.bounds.size,NO, 0);

    //绘制图片
    [_imageView.image drawInRect:_imageView.bounds];

    //获取当前上下文
    CGContextRef ctx=UIGraphicsGetCurrentContext();

    //擦除范围大小
    CGFloat wh=20;
    CGRect clearRect= CGRectMake(curP.x, curP.y, wh, wh);

    //擦除图片
    CGContextClearRect(ctx, clearRect);

    //生成新的图片
    UIImage *image=UIGraphicsGetImageFromCurrentImageContext();

    //关闭上下文
    UIGraphicsEndImageContext();

    //给imageView赋值
    _imageView.image=image;
}
@end

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