项目需求：图片浏览器（可以左右切换，需要支持手势缩放的功能）https://github.com/Shannoon/XLPhotoBrowser.git ，网上搜罗了很多框架不合适。感谢魏希的分享http://www.jianshu.com/p/03c81ee888f4 。现在贴出来以后备用

效果图如下：

photoBrowser.gif

Github：https://github.com/briceZhao/ZoomingImageBrowser

代码

• AZCollectionViewCell.m中

- (void)configSubViews{
    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.bounds];
    scrollView.delegate = self;
    scrollView.maximumZoomScale = 3.0;//最大缩放倍数
    scrollView.minimumZoomScale = 1.0;//最小缩放倍数
    scrollView.showsVerticalScrollIndicator = NO;
    scrollView.showsHorizontalScrollIndicator = NO;
    scrollView.backgroundColor = [UIColor blackColor];
    [self addSubview:scrollView];
    self.scrollView = scrollView;
    
    UIImageView *imageView = [[UIImageView alloc] init];
    imageView.userInteractionEnabled = YES;//在UIImageView上加手势识别，打开用户交互
    UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];
    [doubleTap setNumberOfTapsRequired:2];
    [imageView addGestureRecognizer:doubleTap];//添加双击手势
    [scrollView addSubview:imageView];
    self.imageView = imageView;
}

• 属性的setImage方法中重新设置UIImageView的图片和尺寸以及ScrollView的缩放比例

- (void)setImage:(UIImage *)image{
    _image = image;
    self.imageView.image = image;
    CGFloat width = image.size.width;
    CGFloat height = image.size.height;
    CGFloat maxHeight = self.scrollView.bounds.size.height;
    CGFloat maxWidth = self.scrollView.bounds.size.width;
    //如果图片尺寸大于view尺寸，按比例缩放
    if(width > maxWidth || height > width){
        CGFloat ratio = height / width;
        CGFloat maxRatio = maxHeight / maxWidth;
        if(ratio < maxRatio){
            width = maxWidth;
            height = width*ratio;
        }else{
            height = maxHeight;
            width = height / ratio;
        }
    }
    self.scrollView.contentSize = CGSizeMake(width, height);
    [self.scrollView setZoomScale:1.f];
    self.imageView.frame = CGRectMake((maxWidth - width) / 2, (maxHeight - height) / 2, width, height);
    [self.scrollView layoutIfNeeded];
}

• 实现UIScrollViewDelegate，真正的图片缩放处理

#pragma mark UIScrollViewDelegate
//指定缩放UIScrolleView时，缩放UIImageView来适配
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
    return self.imageView;
}

//缩放后让图片显示到屏幕中间
-(void)scrollViewDidZoom:(UIScrollView *)scrollView{
    CGSize originalSize = _scrollView.bounds.size;
    CGSize contentSize = _scrollView.contentSize;
    CGFloat offsetX = originalSize.width > contentSize.width ? (originalSize.width - contentSize.width) / 2 : 0;
    CGFloat offsetY = originalSize.height > contentSize.height ? (originalSize.height - contentSize.height) / 2 : 0;
    self.imageView.center = CGPointMake(contentSize.width / 2 + offsetX, contentSize.height / 2 + offsetY);
}

- (void)handleDoubleTap:(UITapGestureRecognizer *)recongnizer
{
    UIGestureRecognizerState state = recongnizer.state;
    switch (state) {
        case UIGestureRecognizerStateBegan:
            break;
        case UIGestureRecognizerStateChanged:
            break;
        case UIGestureRecognizerStateCancelled:
        case UIGestureRecognizerStateEnded:
        {
            //以点击点为中心，放大图片
            CGPoint touchPoint = [recongnizer locationInView:recongnizer.view];
            BOOL zoomOut = self.scrollView.zoomScale == self.scrollView.minimumZoomScale;
            CGFloat scale = zoomOut?self.scrollView.maximumZoomScale:self.scrollView.minimumZoomScale;
            [UIView animateWithDuration:0.3 animations:^{
                self.scrollView.zoomScale = scale;
                if(zoomOut){
                    CGFloat x = touchPoint.x*scale - self.scrollView.bounds.size.width / 2;
                    CGFloat maxX = self.scrollView.contentSize.width-self.scrollView.bounds.size.width;
                    CGFloat minX = 0;
                    x = x > maxX ? maxX : x;
                    x = x < minX ? minX : x;
                    
                    CGFloat y = touchPoint.y * scale-self.scrollView.bounds.size.height / 2;
                    CGFloat maxY = self.scrollView.contentSize.height-self.scrollView.bounds.size.height;
                    CGFloat minY = 0;
                    y = y > maxY ? maxY : y;
                    y = y < minY ? minY : y;
                    self.scrollView.contentOffset = CGPointMake(x, y);
                }
            }];
            
        }
            break;
        default:break;
    }
}

以上的代码就能实现图片轮播或者图片浏览器/照片查看器等等的浏览图片类，手势缩放的效果了，以上代码参考了魏希的分享http://www.jianshu.com/p/03c81ee888f4 ， 感谢原作者。贴出来希望更多的人能用上这个方法