Parasitemia/ParasitemiaCore/MatchingEllipses.fs

   1 module ParasitemiaCore.MatchingEllipses
   2
   3 open System
   4 open System.Drawing
   5 open System.Linq
   6 open System.Collections
   7 open System.Collections.Generic
   8
   9 open Types
  10 open Utils
  11
  12 // All ellipses with a score below this are removed.
  13 let matchingScoreThreshold = 0.4f
  14 let matchingScorePower = 20.f
  15 let windowSizeRadiusFactor = 1.f / 2.f
  16 let minimumDistanceFromCenterRadiusFactor = 1.f / 3.f
  17
  18 type private EllipseScoreFlaggedKd (matchingScore: float32, e: Ellipse) =
  19     let mutable matchingScore = matchingScore
  20
  21     member this.Ellipse = e
  22
  23     member this.MatchingScore = matchingScore
  24
  25     member this.AddMatchingScore (score: float32) =
  26         matchingScore <- matchingScore + score
  27
  28     member val Processed = false with get, set
  29     member val Removed = false with get, set
  30
  31     interface KdTree.I2DCoords with
  32         member this.X = this.Ellipse.Cx
  33         member this.Y = this.Ellipse.Cy
  34
  35 type MatchingEllipses (radius: float32) =
  36     let ellipses = List<EllipseScoreFlaggedKd>()
  37
  38     member this.Add (e: Ellipse) =
  39         ellipses.Add(EllipseScoreFlaggedKd(0.f, e))
  40
  41     member this.Ellipses : Ellipse list =
  42         List.ofSeq ellipses |> List.map (fun e -> e.Ellipse)
  43
  44     member this.PrunedEllipses : Ellipse list =
  45         if ellipses.Count = 0
  46         then
  47             []
  48         else
  49             // 1) Create a kd-tree from the ellipses list.
  50             let tree = KdTree.Tree.BuildTree (List.ofSeq ellipses)
  51
  52             // 2) Compute the matching score of each ellipses.
  53             let windowSize = radius * windowSizeRadiusFactor
  54             for e in ellipses do
  55                 e.Processed <- true
  56                 let areaE = e.Ellipse.Area
  57                 let window = { KdTree.minX = e.Ellipse.Cx - windowSize / 2.f
  58                                KdTree.maxX = e.Ellipse.Cx + windowSize / 2.f
  59                                KdTree.minY = e.Ellipse.Cy - windowSize / 2.f
  60                                KdTree.maxY = e.Ellipse.Cy + windowSize / 2.f }
  61                 for other in tree.Search window do
  62                     if not other.Processed
  63                     then
  64                         let areaOther = other.Ellipse.Area
  65                         match EEOver.EEOverlapArea e.Ellipse other.Ellipse with
  66                         | Some (overlapArea, _, _)
  67                             // Because of approximation error, see https://github.com/chraibi/EEOver/issues/4
  68                             when overlapArea - areaE < 1.f && overlapArea - areaOther < 1.f ->
  69                                 let matchingScore = (2.f * overlapArea / (areaE + areaOther)) ** matchingScorePower
  70                                 other.AddMatchingScore(matchingScore)
  71                                 e.AddMatchingScore(matchingScore)
  72                         | _ -> ()
  73
  74             // 3) Remove ellipses whose center is near the center of another ellipse with a better score.
  75             for e in ellipses do
  76                 if e.MatchingScore < matchingScoreThreshold
  77                 then
  78                     e.Removed <- true
  79                 else
  80                     let window = { KdTree.minX = e.Ellipse.Cx - e.Ellipse.A
  81                                    KdTree.maxX = e.Ellipse.Cx + e.Ellipse.A
  82                                    KdTree.minY = e.Ellipse.Cy - e.Ellipse.A
  83                                    KdTree.maxY = e.Ellipse.Cy + e.Ellipse.A }
  84                     for other in tree.Search window do
  85                         if not other.Removed && e.MatchingScore > other.MatchingScore
  86                         then
  87                             // Case where ellipses are too close.
  88                             if distanceTwoPoints (PointF(e.Ellipse.Cx, e.Ellipse.Cy)) (PointF(other.Ellipse.Cx, other.Ellipse.Cy)) < minimumDistanceFromCenterRadiusFactor * e.Ellipse.B
  89                             then
  90                                 other.Removed <- true
  91                             else
  92                                 // Case where ellipses are overlapped.
  93                                 match EEOver.EEOverlapArea e.Ellipse other.Ellipse with
  94                                 | Some (overlapArea, _, _) when e.Ellipse.Area < 1.1f * overlapArea || other.Ellipse.Area < 1.1f * overlapArea ->
  95                                     other.Removed <- true
  96                                 | _ ->
  97                                     ()
  98             ellipses
  99             |> List.ofSeq
 100             |> List.filter (fun e -> not e.Removed)
 101             |> List.sortWith (fun e1 e2 -> e2.MatchingScore.CompareTo(e1.MatchingScore))
 102             |> List.map (fun e -> e.Ellipse)
 103