anchor.diff:      BottomRight: Point
       BottomLeft: Point }
   
  -//inclusive coordinates,
  -//N.B. OpenCV exludes second range value for matrix operations which isn't currently accounted for
  +(*
  +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))
  
positive.code:             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
      let activeKeys = if activeKeys.Length < 4 then activeKeys |> List.map fst else []
      activeKeys, keyImages
  
  
negative.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
  let THRESHOLD = 130.
  
  type KeyPolygon = {
  