IOS中实现图片全屏预览的功能

//
// ViewController.m
// XWZoomImageView
//
// Created by xiao on 15/11/13.
// Copyright © 2015年 xiao. All rights reserved.
//

#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;
}

.h文件-----------------------------------------------------------------
#import
@interface ZoomImage : NSObject
/**
 *@brief点击图片放大,再次点击缩小
 *
 *@param oldImageView 头像所在的imageView
 */
+(void)showImage:(UIImageView*)avatarImageView;
@end
.m文件-----------------------------------------------------------------
#import "ZoomImage.h"
static CGRect oldframe;
@implementation ZoomImage
+(void)showImage:(UIImageView*)avatarImageView
{
 UIImage *image =avatarImageView.image;
 // 获得根窗口
 UIWindow *window =[UIApplication sharedApplication].keyWindow;
 UIView *backgroundView =[[UIView alloc]initWithFrame:CGRectMake(0, 0, WIDTH, HEIGHT)];
 oldframe =[avatarImageView convertRect:avatarImageView.bounds toView:window];
 backgroundView.backgroundColor =[UIColor blackColor];
 backgroundView.alpha =0.5;
 UIImageView *imageView =[[UIImageView alloc]initWithFrame:oldframe];
 imageView.image =image;
 imageView.tag =1;
 [backgroundView addSubview:imageView];
 [window addSubview:backgroundView];
 //点击图片缩小的手势
 UITapGestureRecognizer *tap =[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(hideImage:)];
 [backgroundView addGestureRecognizer:tap];
 [UIView animateWithDuration:0.3 animations:^{
  imageView.frame =CGRectMake(0,([UIScreen mainScreen].bounds.size.height-image.size.height*[UIScreen mainScreen].bounds.size.width/image.size.width)/2, [UIScreen mainScreen].bounds.size.width, image.size.height*[UIScreen mainScreen].bounds.size.width/image.size.width);
  backgroundView.alpha =1;
 }];
}
+(void)hideImage:(UITapGestureRecognizer *)tap{
 UIView *backgroundView =tap.view;
 UIImageView *imageView =(UIImageView *)[tap.view viewWithTag:1];
 [UIView animateWithDuration:0.3 animations:^{
  imageView.frame =oldframe;
  backgroundView.alpha =0;  
 } completion:^(BOOL finished) {
  [backgroundView removeFromSuperview];
 }];
}