title: Why does imageio.imread sometimes return an `imageio.core.util.Array` instead of a numpy array?
body: <p>In the <a href="https://imageio.readthedocs.io/en/stable/userapi.html#imageio.imread" rel="nofollow noreferrer">docs for imageio</a> it says that <code>imageio.imread</code> returns a numpy array. This has been my experience most of the time, but sometimes it returns an <code>imageio.core.util.Array</code> object. <code>imageio.core.util.array</code> is only mentioned once in the <a href="https://readthedocs.org/projects/imageio/downloads/pdf/stable/" rel="nofollow noreferrer">imageio documentation</a>, and just noted that <code>imageio.core.Image</code> is an alias of it. I don't have a small example to provide because I only see it when I'm loading certain images, but I found that it happens in the <a href="http://scipy-lectures.org/advanced/image_processing/" rel="nofollow noreferrer">scipy image processing guide</a>.</p>