anchor.diff:              findChangedKeyImages keyImages previousKeyImages |> List.ofSeq
           else
               []
  -    //activeKeys |> Seq.iter (fun (key, sum) -> printfn "key: %A, sum: %d" key sum)
  -    //printfn ""
  -
  -    //avoid spamming with cars and crowds of people
  +
  +    //vague attempt to avoid spamming with cars and crowds of people
       let activeKeys = if activeKeys.Length < 4 then activeKeys |> List.map fst else []
       activeKeys, keyImages
  -
  
positive.code: let GRAYSCALE_MODE = true
  let IMAGE_READ_MODE = if GRAYSCALE_MODE then ImreadModes.GrayScale else ImreadModes.Color
  let MAT_TYPE = if GRAYSCALE_MODE then MatType.CV_8UC1 else MatType.CV_8UC3
  
  //thresholding images
  let THRESHOLD = 130.
  
  type KeyPolygon = {
  
negative.code:     BottomRight: Point
      BottomLeft: Point }
  
  (*
  These are inclusive coordinates
  FWIW OpenCV exludes second range value for matrix operations which FWIW isn't currently accounted for, but these are only approximate anyway
  *)
  let coordsTopAndBottom =
      [|
          (Point(310, 200), Point(275, 214))
  