Calcultate Optical Flow PyrLK 2
' inspired by Opencv lkdemo.c sample
' by Giuseppe Di Santo - Studio IT
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms
Imports Emgu.CV
Imports Emgu.CV.Structure
Partial Public Class cvCalcOpticalFlowPyrLK2
Inherits Form
Private _capture As Capture
Private ActualFrameNumber As Integer = 0
Private ActualFrame As Image(Of Bgr, Byte), NextFrame As Image(Of Bgr, Byte), OpticalFlowFrame As Image(Of Bgr, Byte)
Private ActualGrayFrame As Image(Of Gray, Byte), NextGrayFrame As Image(Of Gray, Byte)
Private ActualFeature As PointF()()
Private NextFeature As PointF()
Private Status As Byte()
Private TrackError As Single()
Private newPoint As PointF
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
AcquireInputVideo()
AddHandler Application.Idle, New EventHandler(AddressOf Optical_Flow_Worker)
End Sub
Private Sub Optical_Flow_Worker(ByVal sender As Object, ByVal e As EventArgs)
' the actual frame
_capture.SetCaptureProperty(Emgu.CV.CvEnum.CAP_PROP.CV_CAP_PROP_POS_FRAMES, ActualFrameNumber)
ActualFrame = _capture.QueryFrame().Flip(Emgu.CV.CvEnum.FLIP.HORIZONTAL)
ActualGrayFrame = ActualFrame.Convert(Of Gray, [Byte])()
' the next frame
NextFrame = _capture.QueryFrame().Flip(Emgu.CV.CvEnum.FLIP.HORIZONTAL)
NextGrayFrame = NextFrame.Convert(Of Gray, [Byte])()
' We extract some features to be tracked to compute optical flow
If ActualFeature Is Nothing Then
ActualFeature = ActualGrayFrame.GoodFeaturesToTrack(300, 0.01, 10, 5)
ActualGrayFrame.FindCornerSubPix(ActualFeature, New System.Drawing.Size(10, 10), New System.Drawing.Size(-1, -1), New MCvTermCriteria(20, 0.03))
Else
' Compute optical flow using Lukas Kanade Method
ComputeSparseOpticalFlow()
OpticalFlowFrame = New Image(Of Bgr, [Byte])(ActualFrame.Width, ActualFrame.Height)
OpticalFlowFrame = NextFrame.Copy()
For i As Integer = 0 To ActualFeature(0).Length - 1
DrawTrackedFeatures(i)
Next
ActualFeature(0) = NextFeature
End If
ActualFrameNumber += 1
' Frame binding to emguCV imageboxes
Me.imageBox1.Image = OpticalFlowFrame
'this.imageBox1.Image = ActualGrayFrame;
End Sub
Private Sub DrawTrackedFeatures(ByVal i As Integer)
OpticalFlowFrame.Draw(New CircleF(New PointF(ActualFeature(0)(i).X, ActualFeature(0)(i).Y), 1.0F), New Bgr(Color.Red), 2)
End Sub
Private Sub DrawFlowVectors(ByVal i As Integer)
Dim p As System.Drawing.Point = New Point()
Dim q As System.Drawing.Point = New Point()
p.X = CInt(Math.Truncate(ActualFeature(0)(i).X))
p.Y = CInt(Math.Truncate(ActualFeature(0)(i).Y))
q.X = CInt(Math.Truncate(NextFeature(i).X))
q.Y = CInt(Math.Truncate(NextFeature(i).Y))
Dim angle As Double
angle = Math.Atan2(CDbl(p.Y) - q.Y, CDbl(p.X) - q.X)
Dim line As New LineSegment2D(p, q)
OpticalFlowFrame.Draw(line, New Bgr(255, 255, 255), 1)
p.X = CInt(Math.Truncate(q.X + 20 * Math.Cos(angle + Math.PI / 4)))
p.Y = CInt(Math.Truncate(q.Y + 20 * Math.Sin(angle + Math.PI / 4)))
OpticalFlowFrame.Draw(New LineSegment2D(p, q), New Bgr(255, 255, 255), 1)
p.X = CInt(Math.Truncate(q.X + 20 * Math.Cos(angle - Math.PI / 4)))
p.Y = CInt(Math.Truncate(q.Y + 20 * Math.Sin(angle - Math.PI / 4)))
OpticalFlowFrame.Draw(New LineSegment2D(p, q), New Bgr(255, 255, 255), 1)
End Sub
Private Sub AcquireInputVideo()
_capture = New Capture()
_capture.QueryFrame()
End Sub
Private Sub ImageBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ImageBox1.MouseDown
newPoint = New PointF(e.X, e.Y)
Dim temp As PointF() = New PointF(0) {}
temp(0) = newPoint
ActualFeature = New PointF(0)() {}
ActualFeature(0) = temp
ActualGrayFrame.FindCornerSubPix(ActualFeature, New System.Drawing.Size(10, 10), New System.Drawing.Size(-1, -1), New MCvTermCriteria(20, 0.03))
End Sub
'Private Sub imagebox1_MouseClick(ByVal sender As Object, ByVal e As MouseEventArgs) Handles ImageBox1.Click
' newPoint = New PointF(e.X, e.Y)
' Dim temp As PointF() = New PointF(0) {}
' temp(0) = newPoint
' ActualFeature = New PointF(0)() {}
' ActualFeature(0) = temp
' ActualGrayFrame.FindCornerSubPix(ActualFeature, New System.Drawing.Size(10, 10), New System.Drawing.Size(-1, -1), New MCvTermCriteria(20, 0.03))
'End Sub
Private Sub ComputeSparseOpticalFlow()
' Compute optical flow using pyramidal Lukas Kanade Method
OpticalFlow.PyrLK(ActualGrayFrame, NextGrayFrame, ActualFeature(0), New System.Drawing.Size(10, 10), 3, New MCvTermCriteria(20, 0.03), _
NextFeature, Status, TrackError)
End Sub
End Class
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