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 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 =
  58                     {
  59                         KdTree.minX = e.Ellipse.Cx - windowSize / 2.f
  60                         KdTree.maxX = e.Ellipse.Cx + windowSize / 2.f
  61                         KdTree.minY = e.Ellipse.Cy - windowSize / 2.f
  62                         KdTree.maxY = e.Ellipse.Cy + windowSize / 2.f
  63                     }
  64                 for other in tree.Search window do
  65                     if not other.Processed then
  66                         let areaOther = other.Ellipse.Area
  67                         match EEOver.EEOverlapArea e.Ellipse other.Ellipse with
  68                         | Some (overlapArea, _, _)
  69                             // Because of approximation error, see https://github.com/chraibi/EEOver/issues/4
  70                             when overlapArea - areaE < 1.f && overlapArea - areaOther < 1.f ->
  71                                 let matchingScore = (2.f * overlapArea / (areaE + areaOther)) ** matchingScorePower
  72                                 other.AddMatchingScore matchingScore
  73                                 e.AddMatchingScore matchingScore
  74                         | _ -> ()
  75
  76             // 3) Remove ellipses whose center is near the center of another ellipse with a better score.
  77             let matchingScoreThreshold = matchingScoreThresholdPerRadiusUnit * radius
  78             for e in ellipses do
  79                 if e.MatchingScore < matchingScoreThreshold then
  80                     e.Removed <- true
  81                 else
  82                     let window =
  83                         {
  84                             KdTree.minX = e.Ellipse.Cx - e.Ellipse.A
  85                             KdTree.maxX = e.Ellipse.Cx + e.Ellipse.A
  86                             KdTree.minY = e.Ellipse.Cy - e.Ellipse.A
  87                             KdTree.maxY = e.Ellipse.Cy + e.Ellipse.A
  88                         }
  89                     for other in tree.Search window do
  90                         if not other.Removed && e.MatchingScore > other.MatchingScore then
  91                             // Case where ellipses are too close.
  92                             if distanceTwoPoints (PointF (e.Ellipse.Cx, e.Ellipse.Cy)) (PointF (other.Ellipse.Cx, other.Ellipse.Cy)) < minimumDistanceFromCenterRadiusFactor * e.Ellipse.B then
  93                                 other.Removed <- true
  94                             else
  95                                 // Case where ellipses are overlapped.
  96                                 match EEOver.EEOverlapArea e.Ellipse other.Ellipse with
  97                                 | Some (overlapArea, _, _) when e.Ellipse.Area < minimumAreaFactor * overlapArea || other.Ellipse.Area < minimumAreaFactor * overlapArea ->
  98                                     other.Removed <- true
  99                                 | _ ->
 100                                     ()
 101             ellipses
 102             |> List.ofSeq
 103             |> List.filter (fun e -> not e.Removed)
 104             |> List.sortWith (fun e1 e2 -> e2.MatchingScore.CompareTo e1.MatchingScore)
 105             |> List.map (fun e -> e.Ellipse)
 106