iOS 图片浏览的放大缩小

#pragma mark -- UIScrollViewDelegate
//返回需要缩放的视图控件 缩放过程中
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    return self.imageView;
}

//开始缩放
- (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(UIView *)view{
    NSLog(@"开始缩放");
}
//结束缩放
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale{
    NSLog(@"结束缩放");
}

//缩放中
- (void)scrollViewDidZoom:(UIScrollView *)scrollView {
    // 延中心点缩放
    CGFloat imageScaleWidth = scrollView.zoomScale * self.imageNormalWidth;
    CGFloat imageScaleHeight = scrollView.zoomScale * self.imageNormalHeight;
  
    CGFloat imageX = 0;
    CGFloat imageY = 0;
     imageX = floorf((self.frame.size.width - imageScaleWidth) / 2.0);
     imageY = floorf((self.frame.size.height - imageScaleHeight) / 2.0);
     self.imageView.frame = CGRectMake(imageX, imageY, imageScaleWidth, imageScaleHeight);
    
}