图片缩放并居中显示

#import "ViewController.h"

@interface ViewController () <UIScrollViewDelegate> // 遵循代理协议
@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
@property (weak, nonatomic) IBOutlet UIImageView *catView;

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
// 设置滚动内容
self.scrollView.contentSize = self.catView.frame.size;

// 设置代理
self.scrollView.delegate = self;

// 设置缩放尺寸
self.scrollView.maximumZoomScale = 2.0;
self.scrollView.minimumZoomScale = 0.2;
}

// 当用户使用捏合手势的时候开始缩放
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return self.catView;
}

// 使图片缩放后保持在屏幕中间
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
CGFloat x = (self.scrollView.frame.size.width - self.catView.frame.size.width) * 0.5;
CGFloat y = (self.scrollView.frame.size.height - self.catView.frame.size.height) * 0.5;

self.scrollView.contentInset = UIEdgeInsetsMake(y,x, 0, 0);
}

@end