title: How to read image from in memory buffer (StringIO) or from url with opencv python library
body: <p>Just share a way to create opencv image object from in memory buffer or from url to improve performance.</p>
  
  <p>Sometimes we get image binary from url, to avoid additional file IO, we want to <strong>imread</strong> this image from in memory buffer or from url, but imread only supports read image from file system with path.</p>