Split the module 'ImgTools' in many modules.

[master-thesis.git] / Parasitemia / ParasitemiaCore / ImgTools / Edges.fs

diff --git a/Parasitemia/ParasitemiaCore/ImgTools/Edges.fs b/Parasitemia/ParasitemiaCore/ImgTools/Edges.fs
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+++ b/Parasitemia/ParasitemiaCore/ImgTools/Edges.fs
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+module ParasitemiaCore.Edges
+
+open System
+open System.Drawing
+open System.Collections.Generic
+
+open Emgu.CV
+open Emgu.CV.Structure
+
+open Const
+open Histogram
+open Otsu
+
+/// <summary>
+/// Find edges of an image by using the Canny approach.
+/// The thresholds are automatically defined with otsu on gradient magnitudes.
+/// </summary>
+/// <param name="img"></param>
+let find (img: Image<Gray, float32>) : Matrix<byte> * Matrix<float32> * Matrix<float32> =
+    let w = img.Width
+    let h = img.Height
+
+    use sobelKernel =
+        new Matrix<float32>(array2D [[ 1.0f; 0.0f; -1.0f ]
+                                     [ 2.0f; 0.0f; -2.0f ]
+                                     [ 1.0f; 0.0f; -1.0f ]])
+
+    let xGradient = new Matrix<float32>(img.Size)
+    let yGradient = new Matrix<float32>(img.Size)
+    CvInvoke.Filter2D(img, xGradient, sobelKernel, Point(1, 1))
+    CvInvoke.Filter2D(img, yGradient, sobelKernel.Transpose(), Point(1, 1))
+
+    use magnitudes = new Matrix<float32>(xGradient.Size)
+    use angles = new Matrix<float32>(xGradient.Size)
+    CvInvoke.CartToPolar(xGradient, yGradient, magnitudes, angles) // Compute the magnitudes and angles.
+
+    let thresholdHigh, thresholdLow =
+        let sensibilityHigh = 0.1f
+        let sensibilityLow = 0.0f
+        let threshold, _, _ = otsu (histogramMat magnitudes 300)
+        threshold + (sensibilityHigh * threshold), threshold - (sensibilityLow * threshold)
+
+    // Non-maximum suppression.
+    use nms = new Matrix<byte>(xGradient.Size)
+
+    let nmsData = nms.Data
+    let anglesData = angles.Data
+    let magnitudesData = magnitudes.Data
+    let xGradientData = xGradient.Data
+    let yGradientData = yGradient.Data
+
+    for i in 0 .. h - 1 do
+        nmsData.[i, 0] <- 0uy
+        nmsData.[i, w - 1] <- 0uy
+
+    for j in 0 .. w - 1 do
+        nmsData.[0, j] <- 0uy
+        nmsData.[h - 1, j] <- 0uy
+
+    for i in 1 .. h - 2 do
+        for j in 1 .. w - 2 do
+            let vx = xGradientData.[i, j]
+            let vy = yGradientData.[i, j]
+            if vx <> 0.f || vy <> 0.f
+            then
+                let angle = anglesData.[i, j]
+
+                let vx', vy' = abs vx, abs vy
+                let ratio2 = if vx' > vy' then vy' / vx' else vx' / vy'
+                let ratio1 = 1.f - ratio2
+
+                let mNeigbors (sign: int) : float32 =
+                    if angle < PI / 4.f
+                    then ratio1 * magnitudesData.[i, j + sign] + ratio2 * magnitudesData.[i + sign, j + sign]
+                    elif angle < PI / 2.f
+                    then ratio2 * magnitudesData.[i + sign, j + sign] + ratio1 * magnitudesData.[i + sign, j]
+                    elif angle < 3.f * PI / 4.f
+                    then ratio1 * magnitudesData.[i + sign, j] + ratio2 * magnitudesData.[i + sign, j - sign]
+                    elif angle < PI
+                    then ratio2 * magnitudesData.[i + sign, j - sign] + ratio1 * magnitudesData.[i, j - sign]
+                    elif angle < 5.f * PI / 4.f
+                    then ratio1 * magnitudesData.[i, j - sign] + ratio2 * magnitudesData.[i - sign, j - sign]
+                    elif angle < 3.f * PI / 2.f
+                    then ratio2 * magnitudesData.[i - sign, j - sign] + ratio1 * magnitudesData.[i - sign, j]
+                    elif angle < 7.f * PI / 4.f
+                    then ratio1 * magnitudesData.[i - sign, j] + ratio2 * magnitudesData.[i - sign, j + sign]
+                    else ratio2 * magnitudesData.[i - sign, j + sign] + ratio1 * magnitudesData.[i, j + sign]
+
+                let m = magnitudesData.[i, j]
+                if m >= thresholdLow && m > mNeigbors 1 && m > mNeigbors -1
+                then
+                    nmsData.[i, j] <- 1uy
+
+    // suppressMConnections nms // It's not helpful for the rest of the process (ellipse detection).
+
+    let edges = new Matrix<byte>(xGradient.Size)
+    let edgesData = edges.Data
+
+    // Hysteresis thresholding.
+    let toVisit = Stack<Point>()
+    for i in 0 .. h - 1 do
+        for j in 0 .. w - 1 do
+            if nmsData.[i, j] = 1uy && magnitudesData.[i, j] >= thresholdHigh
+            then
+                nmsData.[i, j] <- 0uy
+                toVisit.Push(Point(j, i))
+                while toVisit.Count > 0 do
+                    let p = toVisit.Pop()
+                    edgesData.[p.Y, p.X] <- 1uy
+                    for i' in -1 .. 1  do
+                        for j' in -1 .. 1 do
+                            if i' <> 0 || j' <> 0
+                            then
+                                let ni = p.Y + i'
+                                let nj = p.X + j'
+                                if ni >= 0 && ni < h && nj >= 0 && nj < w && nmsData.[ni, nj] = 1uy
+                                then
+                                    nmsData.[ni, nj] <- 0uy
+                                    toVisit.Push(Point(nj, ni))
+
+    edges, xGradient, yGradient
\ No newline at end of file