UIScrollView做图片缩放

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    UIScrollView * scrollView = [[UIScrollView alloc]initWithFrame:self.view.frame];
    //第一步设置代理
    scrollView.delegate = self;
    [self.view addSubview:scrollView];
    //第二步设置缩放倍数
    scrollView.minimumZoomScale = 1.0;
    scrollView.maximumZoomScale = 3.0;
    
    //图片
    UIImageView * imageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"详细信息"]];
    [scrollView addSubview:imageView];
    self.imageView = imageView;
}

实现代理

//第三步，缩放的view
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
    return self.imageView;
}