Shape Detection

' translated in VB:NET from c#

' by Giuseppe Di Santo - Studio IT

Imports Emgu.CV.UI

Imports Emgu.CV

Imports Emgu.CV.Structure

Imports System

Imports System.ComponentModel

Imports System.Drawing

Imports System.Windows.Forms

Imports System.Collections.Generic

Public Class ShapeDetection

    Private Sub loadImageButton_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles loadImageButton.Click

        Select Case Me.openFileDialog1.ShowDialog

            Case DialogResult.OK, DialogResult.Yes

                Me.fileNameTextBox.Text = Me.openFileDialog1.FileName

                Exit Select

        End Select

    End Sub

    Public Sub PerformShapeDetection()

        If (Me.fileNameTextBox.Text <> String.Empty) Then

            ' Load the image from file and resize it for display

            Dim img As Emgu.CV.Image(Of Emgu.CV.Structure.Bgr, Byte) = New Emgu.CV.Image(Of Emgu.CV.Structure.Bgr, Byte)(fileNameTextBox.Text).Resize(400, 400, Emgu.CV.CvEnum.INTER.CV_INTER_LINEAR, True)

            ' Convert the image to grayscale and filter out the noise

            Dim gray As Emgu.CV.Image(Of Emgu.CV.Structure.Gray, Byte) = img.Convert(Of Gray, Byte).PyrDown.PyrUp()

            Dim cannyThreshold As New Gray(180)

            Dim cannyThresholdLinking As New Gray(120)

            Dim circleAccumulatorThreshold As New Gray(500)

            Dim circles As CircleF() = gray.HoughCircles(cannyThreshold, circleAccumulatorThreshold, 4.0, 15.0, 5, 0)(0) 'Get the circles from the first channel

            Dim cannyEdges As Image(Of Gray, Byte) = gray.Canny(cannyThreshold, cannyThresholdLinking)

            Dim lines As LineSegment2D() = cannyEdges.HoughLinesBinary(1, Math.PI / 45.0, 20, 30, 10)(0)

            Dim triangleList As New List(Of Triangle2DF)()

            Dim boxList As New List(Of MCvBox2D)() 'a box is a rotated rectangle

            Using storage As New MemStorage()

                'allocate storage for contour approximation

                Dim contours As Contour(Of Point) = cannyEdges.FindContours(Emgu.CV.CvEnum.CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE, Emgu.CV.CvEnum.RETR_TYPE.CV_RETR_LIST, storage)

                While contours IsNot Nothing

                    Dim currentContour As Contour(Of Point) = contours.ApproxPoly(contours.Perimeter * 0.05, storage)

                    If currentContour.Area > 250 Then

                        'only consider contours with area greater than 250

                        If currentContour.Total = 3 Then

                            'The contour has 3 vertices, it is a triangle

                            Dim pts As Point() = currentContour.ToArray()

                            triangleList.Add(New Triangle2DF(pts(0), pts(1), pts(2)))

                        ElseIf currentContour.Total = 4 Then

                            'The contour has 4 vertices.

                            ' "determine if all the angles in the contour are within [80, 100] degree"

                            Dim isRectangle As Boolean = True

                            Dim pts As Point() = currentContour.ToArray()

                            Dim edges As LineSegment2D() = PointCollection.PolyLine(pts, True)

                            For i As Integer = 0 To edges.Length - 1

                                Dim angle As Double = Math.Abs(edges((i + 1) Mod edges.Length).GetExteriorAngleDegree(edges(i)))

                                If angle < 80 OrElse angle > 100 Then

                                    isRectangle = False

                                    Exit For

                                End If

                            Next

                            If isRectangle Then

                                boxList.Add(currentContour.GetMinAreaRect())

                            End If

                        End If

                    End If

                    contours = contours.HNext

                End While

            End Using

            originalImageBox.Image = img

            Dim triangleRectangleImage As Image(Of Bgr, Byte) = img.CopyBlank

            Dim triangle As Triangle2DF

            For Each triangle In triangleList

                triangleRectangleImage.Draw(triangle, New Bgr(Color.DarkBlue), 2)

            Next

            Dim box As MCvBox2D

            For Each box In boxList

                triangleRectangleImage.Draw(box, New Bgr(Color.DarkOrange), 2)

            Next

            triangleRectangleImageBox.Image = triangleRectangleImage

            Dim circleImage As Image(Of Bgr, Byte) = img.CopyBlank

            Dim circle As CircleF

            For Each circle In circles

                circleImage.Draw(circle, New Bgr(Color.Brown), 2)

            Next

            circleImageBox.Image = circleImage

            Dim lineImage As Image(Of Bgr, Byte) = img.CopyBlank

            Dim line As LineSegment2D

            For Each line In lines

                lineImage.Draw(line, New Bgr(Color.Green), 2)

            Next

            lineImageBox.Image = lineImage

        End If

    End Sub

    Private Sub fileNameTextBox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles fileNameTextBox.TextChanged

        Me.PerformShapeDetection()

    End Sub

End Class