Parasitemia/ParasitemiaCore/ImgTools/Otsu.fs

   1 module ParasitemiaCore.Otsu
   2
   3 open Histogram
   4
   5 let otsu (hist : Histogram) : float32 * float32 * float32 =
   6     let mutable sumB = 0
   7     let mutable wB = 0
   8     let mutable maximum = 0.0
   9     let mutable level = 0
  10     let sum = hist.data |> Array.mapi (fun i v -> i * v |> float) |> Array.sum
  11
  12     for i = 0 to hist.data.Length - 1 do
  13         wB <- wB + hist.data.[i]
  14         if wB <> 0 then
  15             let wF = hist.total - wB
  16             if wF <> 0 then
  17                 sumB <- sumB + i * hist.data.[i]
  18                 let mB = (float sumB) / (float wB)
  19                 let mF = (sum - float sumB) / (float wF)
  20                 let between = (float wB) * (float wF) * (mB - mF) ** 2.;
  21                 if between >= maximum then
  22                     level <- i
  23                     maximum <- between
  24
  25     let mean1 =
  26         let mutable sum = 0
  27         let mutable nb = 0
  28         for i = 0 to level - 1 do
  29             sum <- sum + i * hist.data.[i]
  30             nb <- nb + hist.data.[i]
  31         (sum + level * hist.data.[level] / 2) / (nb + hist.data.[level] / 2)
  32
  33     let mean2 =
  34         let mutable sum = 0
  35         let mutable nb = 0
  36         for i = level + 1 to hist.data.Length - 1 do
  37             sum <- sum + i * hist.data.[i]
  38             nb <- nb + hist.data.[i]
  39         (sum + level * hist.data.[level] / 2) / (nb + hist.data.[level] / 2)
  40
  41     let toFloat l =
  42         float32 l / float32 hist.data.Length * (hist.max - hist.min) + hist.min
  43
  44     toFloat level, toFloat mean1, toFloat mean2