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 matchingScoreThresholdPerRadiusUnit = 0.07f // For a radius of 1. // 0.25
  14 let matchingScorePower = 20.f
  15 let windowSizeRadiusFactor = 1.f / 2.f // Used when searching for neighbor ellipses.
  16 let minimumDistanceFromCenterRadiusFactor = 1.f / 3.f
  17 let minimumAreaFactor = 1.1f;
  18
  19 type private EllipseScoreFlaggedKd (matchingScore: float32, e: Ellipse) =
  20     let mutable matchingScore = matchingScore
  21
  22     member this.Ellipse = e
  23
  24     member this.MatchingScore = matchingScore
  25
  26     member this.AddMatchingScore (score: float32) =
  27         matchingScore <- matchingScore + score
  28
  29     member val Processed = false with get, set
  30     member val Removed = false with get, set
  31
  32     interface KdTree.I2DCoords with
  33         member this.X = this.Ellipse.Cx
  34         member this.Y = this.Ellipse.Cy
  35
  36 type MatchingEllipses (radius: float32) =
  37     let ellipses = List<EllipseScoreFlaggedKd>()
  38
  39     member this.Add (e: Ellipse) =
  40         ellipses.Add(EllipseScoreFlaggedKd(0.f, e))
  41
  42     member this.Ellipses : Ellipse list =
  43         List.ofSeq ellipses |> List.map (fun e -> e.Ellipse)
  44
  45     member this.PrunedEllipses : Ellipse list =
  46         if ellipses.Count = 0
  47         then
  48             []
  49         else
  50             // 1) Create a kd-tree from the ellipses list.
  51             let tree = KdTree.Tree.BuildTree (List.ofSeq ellipses)
  52
  53             // 2) Compute the matching score of each ellipses.
  54             let windowSize = radius * windowSizeRadiusFactor
  55             for e in ellipses do
  56                 e.Processed <- true
  57                 let areaE = e.Ellipse.Area
  58                 let window = { KdTree.minX = e.Ellipse.Cx - windowSize / 2.f
  59                                KdTree.maxX = e.Ellipse.Cx + windowSize / 2.f
  60                                KdTree.minY = e.Ellipse.Cy - windowSize / 2.f
  61                                KdTree.maxY = e.Ellipse.Cy + windowSize / 2.f }
  62                 for other in tree.Search window do
  63                     if not other.Processed
  64                     then
  65                         let areaOther = other.Ellipse.Area
  66                         match EEOver.EEOverlapArea e.Ellipse other.Ellipse with
  67                         | Some (overlapArea, _, _)
  68                             // Because of approximation error, see https://github.com/chraibi/EEOver/issues/4
  69                             when overlapArea - areaE < 1.f && overlapArea - areaOther < 1.f ->
  70                                 let matchingScore = (2.f * overlapArea / (areaE + areaOther)) ** matchingScorePower
  71                                 other.AddMatchingScore(matchingScore)
  72                                 e.AddMatchingScore(matchingScore)
  73                         | _ -> ()
  74
  75             // 3) Remove ellipses whose center is near the center of another ellipse with a better score.
  76             let matchingScoreThreshold = matchingScoreThresholdPerRadiusUnit * radius
  77             for e in ellipses do
  78                 if e.MatchingScore < matchingScoreThreshold
  79                 then
  80                     e.Removed <- true
  81                 else
  82                     let window = { KdTree.minX = e.Ellipse.Cx - e.Ellipse.A
  83                                    KdTree.maxX = e.Ellipse.Cx + e.Ellipse.A
  84                                    KdTree.minY = e.Ellipse.Cy - e.Ellipse.A
  85                                    KdTree.maxY = e.Ellipse.Cy + e.Ellipse.A }
  86                     for other in tree.Search window do
  87                         if not other.Removed && e.MatchingScore > other.MatchingScore
  88                         then
  89                             // Case where ellipses are too close.
  90                             if distanceTwoPoints (PointF(e.Ellipse.Cx, e.Ellipse.Cy)) (PointF(other.Ellipse.Cx, other.Ellipse.Cy)) < minimumDistanceFromCenterRadiusFactor * e.Ellipse.B
  91                             then
  92                                 other.Removed <- true
  93                             else
  94                                 // Case where ellipses are overlapped.
  95                                 match EEOver.EEOverlapArea e.Ellipse other.Ellipse with
  96                                 | Some (overlapArea, _, _) when e.Ellipse.Area < minimumAreaFactor * overlapArea || other.Ellipse.Area < minimumAreaFactor * overlapArea ->
  97                                     other.Removed <- true
  98                                 | _ ->
  99                                     ()
 100             ellipses
 101             |> List.ofSeq
 102             |> List.filter (fun e -> not e.Removed)
 103             |> List.sortWith (fun e1 e2 -> e2.MatchingScore.CompareTo(e1.MatchingScore))
 104             |> List.map (fun e -> e.Ellipse)
 105