https://my.oschina.net/iq19900204/blog/206816
@interface HYShowImageView : UIScrollView <UIScrollViewDelegate>

//显示图像大图
-(void)showImage:(UIImage*)image inView:(UIView *)parentsView fromRect:(CGRect)rect;

@end
先看一下头文件，继承UIScrollView，实现UIScrollViewDelegate协议。

提供了一个方法ShowImage。

接下来看看这个方法是实现

-(void)showImage:(UIImage*)image inView:(UIView *)parentsView fromRect:(CGRect)rect
{
_oldRect = rect;

[self setFrame:CGRectMake(0, 0, PHOTOWIDTH, PHOTOHEIGHT)];
self.showsHorizontalScrollIndicator = NO;
self.showsVerticalScrollIndicator = NO;

UIImageView *showView = [[UIImageView alloc] initWithFrame:_oldRect];
showView.contentMode = UIViewContentModeScaleAspectFit;
[UIView animateWithDuration:0.5f animations:^{
    [showView setFrame:CGRectMake(0, 0, PHOTOWIDTH, PHOTOHEIGHT)];
}];

[self setBackgroundColor:color_with_rgba(0, 0, 0, 1)];
[parentsView addSubview:self];

[showView setTag:'show'];
[showView setImage:image];   //这个地方也可以用网络的图片
[self addSubview:showView];

//增加两个手势
showView.userInteractionEnabled = YES;
UITapGestureRecognizer* singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleSingleViewTap:)];
[self addGestureRecognizer:singleTap];

UIPinchGestureRecognizer* pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinchView:)];
[self addGestureRecognizer:pinchGesture];

}
增加了两个手势，一个点击取消，一个缩放

//移除图片查看视图
-(void)handleSingleViewTap:(UITapGestureRecognizer *)sender
{
[self setZoomScale:1.0 animated:NO];
[UIView animateWithDuration:0.5f animations:^{
UIImageView *showView = (UIImageView *)[self viewWithTag:'show'];
showView.frame = _oldRect;
self.backgroundColor = color_with_rgba(0, 0, 0, 0.0);
} completion:^(BOOL finished){
[self removeFromSuperview];
}];
}
//缩放图片
-(void)handlePinchView:(UIPinchGestureRecognizer *)sender
{
UIImageView *imageView = (UIImageView *)[self viewWithTag:'show'];
if ([sender state] == UIGestureRecognizerStateBegan) {
_imageHWScale = imageView.image.size.height/imageView.image.size.width;
_beganScale = self.zoomScale;
}

[self setZoomScale:_beganScale * sender.scale];

if ([sender state] == UIGestureRecognizerStateEnded) {
    [self scrollViewEnd];
}

}

• (void)scrollViewEnd
  {
  if (self.zoomScale < 1.0) {
  [self setZoomScale:1.0 animated:YES];
  self.contentOffset = CGPointMake(0, 0);
  } else if (self.zoomScale > 3.0) {
  [self setZoomScale:3.0 animated:YES];
  }
  }
  实现委托的方法：

pragma mark - ScrollView delegate

-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
for (UIView *v in scrollView.subviews){
return v;
}
return nil;
}

• (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
  {
  [self scrollViewEnd];
  }·

• (void)scrollViewDidZoom:(UIScrollView *)scrollView
  {
  UIImageView *imageView = (UIImageView *)[self viewWithTag:'show'];
  _imageHWScale = imageView.image.size.height/imageView.image.size.width;
  if (self.contentOffset.x<=0 && self.contentOffset.y<=0) {
  self.contentOffset = CGPointMake((imageView.width - PHOTOWIDTH)/2, (imageView.width - PHOTOWIDTH));
  }
  }
  总结：

优点：这种缩放方式是使用了ScrollView自带的zoom缩放，所有使用简单

缺点：这种缩放方式如果图片高度不符合屏幕的话，放大后上下会有很大的空白部分（待解决）

推荐使用库：MJPhotoBrowse:http://code4app.com/ios/快速集成图片浏览器/525e06116803fa7b0a000001

原版本有一些问题，我修改了bug到了这里:http://git.oschina.net/jonear/MJPhotoBrowser