title: How can I clean this picture up (opencv-python)?
body: <p>I am really new to opencv. How can I remove the noise in the background without losing info?</p>
  <p>I started with this: and Otsu thresholded it. I've tried erosion, dilation, bilateral filtering. My goal is to get a rectangle on the borders so I can perspective transform the thresholded picture, but it has trouble finding contours. Or maybe is there a different and better approach?</p>