.h文件

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface XQAvatarBrowser : NSObject
/**
 *  @brief  浏览头像
 *
 *  @param  oldImageView    头像所在的imageView
 */
+(void)showImage:(UIImageView*)avatarImageView; 
@end

.m文件

#import "XQAvatarBrowser.h"
static CGRect oldframe;
@implementation XQAvatarBrowser
+(void)showImage:(UIImageView *)avatarImageView{
    UIImage *image=avatarImageView.image;
    UIWindow *window=[UIApplication sharedApplication].keyWindow;
    UIView *backgroundView=[[UIView alloc]initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height)];
    oldframe=[avatarImageView convertRect:avatarImageView.bounds toView:window];
    backgroundView.backgroundColor=[UIColor blackColor];
    backgroundView.alpha=0;
    UIImageView *imageView=[[UIImageView alloc]initWithFrame:oldframe];
    imageView.image=image;
    imageView.tag=1;
    [backgroundView addSubview:imageView];
    [window addSubview:backgroundView];
    
    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;
    } completion:^(BOOL finished) {
        
    }];
}

+(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];
    }];
}
@end

用法

[XQAvatarBrowser showImage:imgView];