点击单张图片的全屏预览和双指捏合缩小放大

#import "ViewController.h"

@interface ViewController ()<UIScrollViewDelegate>
@property (weak, nonatomic) IBOutlet UIImageView *picView;
@property (weak, nonatomic) UIScrollView *scrollView;
@property (weak, nonatomic) UIImageView *lastImageView;
@property (nonatomic, assign)CGRect originalFrame;
@property (nonatomic, assign)BOOL isDoubleTap;
@end
 
@implementation ViewController
 
- (void)viewDidLoad {
 [super viewDidLoad];
  
 self.picView.userInteractionEnabled = YES;
 //添加单击手势
 UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(showZoomImageView:)];
 
 [self.picView addGestureRecognizer:tap];
  
}
 
-(void)showZoomImageView:(UITapGestureRecognizer *)tap
{
 if (![(UIImageView *)tap.view image]) {
  return;
 }
 //scrollView作为背景
 UIScrollView *bgView = [[UIScrollView alloc] init];
 bgView.frame = [UIScreen mainScreen].bounds;
 bgView.backgroundColor = [UIColor blackColor];
 UITapGestureRecognizer *tapBg = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapBgView:)];
 [bgView addGestureRecognizer:tapBg];
  
 UIImageView *picView = (UIImageView *)tap.view;
  
 UIImageView *imageView = [[UIImageView alloc] init];
 imageView.image = picView.image;
 imageView.frame = [bgView convertRect:picView.frame fromView:self.view];
 [bgView addSubview:imageView];
  
 [[[UIApplication sharedApplication] keyWindow] addSubview:bgView];
  
 self.lastImageView = imageView;
 self.originalFrame = imageView.frame;
 self.scrollView = bgView;
 //最大放大比例
 self.scrollView.maximumZoomScale = 1.5;
 self.scrollView.delegate = self;
  
 [UIView animateWithDuration:0.5 animations:^{
  CGRect frame = imageView.frame;
  frame.size.width = bgView.frame.size.width;
  frame.size.height = frame.size.width * (imageView.image.size.height / imageView.image.size.width);
  frame.origin.x = 0;
  frame.origin.y = (bgView.frame.size.height - frame.size.height) * 0.5;
  imageView.frame = frame;
 }];
}
 
-(void)tapBgView:(UITapGestureRecognizer *)tapBgRecognizer
{
 self.scrollView.contentOffset = CGPointZero;
 [UIView animateWithDuration:0.5 animations:^{
  self.lastImageView.frame = self.originalFrame;
  tapBgRecognizer.view.backgroundColor = [UIColor clearColor];
 } completion:^(BOOL finished) {
  [tapBgRecognizer.view removeFromSuperview];
  self.scrollView = nil;
  self.lastImageView = nil;
 }];
}
 
//返回可缩放的视图
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
 return self.lastImageView;
}