模仿微信更改头像，图片局部放大

代码

#import "ViewController.h"

@interface ViewController (){
    UIImageView *showImageView;
    UIImageView *imageView;
  }
@end

@implementation ViewController

- (void)viewDidLoad {
    [superviewDidLoad];
    self.view.backgroundColor = [UIColorgrayColor];
    //女孩图片
    imageView = [[UIImageViewalloc]initWithFrame:CGRectMake(70, 50,241, 360)];
    //  imageView.layer.contents = (__bridge id)([UIImage imageNamed:@"图片0.jpg"].CGImage);
    imageView.image = [UIImageimageNamed:@"图片0.jpg"];
    imageView.alpha =0.4;    
    imageView.userInteractionEnabled =YES;
    [self.viewaddSubview:imageView];
    
    //显示放大的局部图片
    UIImageView *screenShotView = [[UIImageViewalloc]initWithFrame:CGRectMake(0,0, 80,80)];
    //screenShotView.backgroundColor = [UIColor yellowColor];
    screenShotView.backgroundColor = [UIColorclearColor];
    screenShotView.userInteractionEnabled =YES;
    screenShotView.layer.borderColor = [UIColorredColor].CGColor;
    screenShotView.layer.borderWidth =1.0f;
    [imageViewaddSubview:screenShotView];
    // 手势拖动
    UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizeralloc]initWithTarget:self action:@selector(panGestureRecognizer:)];
    [screenShotView addGestureRecognizer:panGesture];
     showImageView = [[UIImageViewalloc]initWithFrame:CGRectMake(100,440, 190,190)];
    showImageView.backgroundColor = [UIColorredColor];
    [self.viewaddSubview:showImageView];
    // Do any additional setup after loading the view, typically from a nib.

}

//移动手势的回调方法
- (void)panGestureRecognizer:(UIPanGestureRecognizer*)panGesture{
    CGPoint point = [panGesturelocationInView:imageView];
    panGesture.view.center =  point;
    CGRect rect = panGesture.view.frame;
    UIImage *newImage = [selfInterceptionUIImageWithImage: imageView.image andRect:rect];
    showImageView.image = newImage;
    // ((UIImageView*)panGesture.view).image = newImage;
}
//截取图片的某一部分
- (UIImage*)InterceptionUIImageWithImage:(UIImage*)image andRect:(CGRect)rect{
    CGImageRef imageRef = image.CGImage;
    CGImageRef imageRefRect =CGImageCreateWithImageInRect(imageRef, rect);
    UIImage *imageRect = [[UIImagealloc] initWithCGImage:imageRefRect];
    return imageRect;   
}
- (void)didReceiveMemoryWarning {
    [superdidReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

效果

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