MJPhotoBrowser 图片放大时，图片太靠下修改

在MJPhotoView.m里面添加如下代码：

- (void)scrollViewDidZoom:(UIScrollView *)scrollView {

CGRect imageViewFrame = _imageView.frame;

CGRect screenBounds = [UIScreen mainScreen].bounds;

if (imageViewFrame.size.height > screenBounds.size.height)

{ imageViewFrame.origin.y = 0.0f; }

else { imageViewFrame.origin.y = (screenBounds.size.height - imageViewFrame.size.height) / 2.0; }

_imageView.frame = imageViewFrame;

}