title: OpenCV Autocropping a thumb from covered camera
body: <p>Problem: My thumb has partially covered one side of my video/photo. What OpenCV tools can detect the maximum x pixel index of the thumb (x_t) and perform a crop to keep the region: [x_t:W, 0:H]. Basically, remove the entire rectangle where the thumb exists to keep the remaining rectangular video. This can be performed once at the beginning of the video and the parameters can be retained.</p>
  
  <p>Thoughts: The thumb appears blurry up close, so a contrast boundary detector is not as robust as I would like. BackgroundSubtraction over the first few frames seems promising, but I can't guarantee the video will be changing. Any other approaches?</p>