How to capture a single frame from the video stream?

[duvix]

I have this code and would like to know how to capture a singe frame and put it in a picture box? The source of the video is a WebCam.

Imports System
Imports System.Diagnostics
Imports System.Drawing
Imports System.Runtime.InteropServices
Imports System.Windows.Forms
Imports DirectShowLib
Imports System.Runtime.InteropServices.ComTypes

Namespace Capture_The_Webcam
    Public Class Form1
        Inherits System.Windows.Forms.Form
        Enum PlayState
            Stopped
            Paused
            Running
            Init
        End Enum
        Dim CurrentState As PlayState = PlayState.Stopped

        Dim D As Integer = Convert.ToInt32("0X8000", 16)
        Public WM_GRAPHNOTIFY As Integer = D + 1

        Dim VideoWindow As IVideoWindow = Nothing
        Dim MediaControl As IMediaControl = Nothing
        Dim MediaEventEx As IMediaEventEx = Nothing
        Dim GraphBuilder As IGraphBuilder = Nothing
        Dim CaptureGraphBuilder As ICaptureGraphBuilder2 = Nothing

        Dim rot As DsROTEntry = Nothing

        <STAThread()> Shared Sub Main()
            Application.Run(New Form1)
        End Sub
        Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
            Form2.Show()

            InitializeComponent()
            CaptureVideo()
        End Sub

        Private Sub InitializeComponent()
            Me.SuspendLayout()
            '
            'Form1
            '
            Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
            Me.ClientSize = New System.Drawing.Size(304, 282)
            Me.Name = "Form1"
            Me.Text = "Video Capture Previewer (PlayCap)"
            Me.ResumeLayout(False)

        End Sub
        Private Sub CaptureVideo()
            Dim hr As Integer = 0
            Dim sourceFilter As IBaseFilter = Nothing
            Try
                GetInterfaces()

                hr = Me.CaptureGraphBuilder.SetFiltergraph(Me.GraphBuilder) 'Specifies filter graph "graphbuilder" for the capture graph builder "captureGraphBuilder" to use.
                Debug.WriteLine("Attach the filter graph to the capture graph : " & DsError.GetErrorText(hr))
                DsError.ThrowExceptionForHR(hr)

                sourceFilter = FindCaptureDevice()

                hr = Me.GraphBuilder.AddFilter(sourceFilter, "Video Capture")
                Debug.WriteLine("Add capture filter to our graph : " & DsError.GetErrorText(hr))
                DsError.ThrowExceptionForHR(hr)

                hr = Me.CaptureGraphBuilder.RenderStream(PinCategory.Preview, MediaType.Video, sourceFilter, Nothing, Nothing)
                Debug.WriteLine("Render the preview pin on the video capture filter : " & DsError.GetErrorText(hr))
                DsError.ThrowExceptionForHR(hr)
               
                Marshal.ReleaseComObject(sourceFilter)

                SetupVideoWindow()

                rot = New DsROTEntry(Me.GraphBuilder)
                Dim hrr As Integer


                hr = Me.MediaControl.Run()
                Debug.WriteLine("Start previewing video data : " & DsError.GetErrorText(hr))
                DsError.ThrowExceptionForHR(hr)
               
                Me.CurrentState = PlayState.Running
                Debug.WriteLine("The currentstate : " & Me.CurrentState.ToString)

            Catch ex As Exception
                MessageBox.Show("An unrecoverable error has occurred.With error : " & ex.ToString)
            End Try
        End Sub

        Private Sub GetInterfaces()
            Dim hr As Integer = 0
            Me.GraphBuilder = CType(New FilterGraph, IGraphBuilder)
            Me.CaptureGraphBuilder = CType(New CaptureGraphBuilder2, ICaptureGraphBuilder2)
            Me.MediaControl = CType(Me.GraphBuilder, IMediaControl)
            Me.VideoWindow = CType(Me.GraphBuilder, IVideoWindow)
            Me.MediaEventEx = CType(Me.GraphBuilder, IMediaEventEx)
            hr = Me.MediaEventEx.SetNotifyWindow(Me.Handle, WM_GRAPHNOTIFY, IntPtr.Zero) 'This method designates a window as the recipient of messages generated by or sent to the current DirectShow object
            DsError.ThrowExceptionForHR(hr) 'ThrowExceptionForHR is a wrapper for Marshal.ThrowExceptionForHR, but additionally provides descriptions for any DirectShow specific error messages.If the hr value is not a fatal error, no exception will be thrown:
            Debug.WriteLine("I started Sub Get interfaces , the result is : " & DsError.GetErrorText(hr))
        End Sub
        Public Function FindCaptureDevice() As IBaseFilter
            Debug.WriteLine("Start the Sub FindCaptureDevice")
            Dim hr As Integer = 0
            Dim classEnum As IEnumMoniker = Nothing
            Dim moniker As IMoniker() = New IMoniker(0) {}
            Dim source As Object = Nothing
            Dim devEnum As ICreateDevEnum = CType(New CreateDevEnum, ICreateDevEnum)
            hr = devEnum.CreateClassEnumerator(FilterCategory.VideoInputDevice, classEnum, 0)
            Debug.WriteLine("Create an enumerator for the video capture devices : " & DsError.GetErrorText(hr))
            DsError.ThrowExceptionForHR(hr)
            Marshal.ReleaseComObject(devEnum)
            If classEnum Is Nothing Then
                Throw New ApplicationException("No video capture device was detected.\r\n\r\n" & _
                               "This sample requires a video capture device, such as a USB WebCam,\r\n" & _
                               "to be installed and working properly.  The sample will now close.")
            End If
            If classEnum.Next(moniker.Length, moniker, IntPtr.Zero) = 0 Then
                Dim iid As Guid = GetType(IBaseFilter).GUID
                moniker(0).BindToObject(Nothing, Nothing, iid, source)
            Else
                Throw New ApplicationException("Unable to access video capture device!")
            End If
            Marshal.ReleaseComObject(moniker(0))
            Marshal.ReleaseComObject(classEnum)
            Return CType(source, IBaseFilter)
        End Function
        Public Sub SetupVideoWindow()
            Dim hr As Integer = 0
            hr = Me.VideoWindow.put_Owner(Me.Handle)
         
            DsError.ThrowExceptionForHR(hr)

            hr = Me.VideoWindow.put_WindowStyle(WindowStyle.Child Or WindowStyle.ClipChildren)
            DsError.ThrowExceptionForHR(hr)

            ResizeVideoWindow()

            hr = Me.VideoWindow.put_Visible(OABool.True)
            DsError.ThrowExceptionForHR(hr)
        End Sub

        Protected Overloads Sub WndProc(ByRef m As Message)
            Select Case m.Msg
                Case WM_GRAPHNOTIFY
                    HandleGraphEvent()
            End Select
            If Not (Me.VideoWindow Is Nothing) Then
                Me.VideoWindow.NotifyOwnerMessage(m.HWnd, m.Msg, m.WParam.ToInt32, m.LParam.ToInt32)
            End If
            MyBase.WndProc(m)

        End Sub
        Public Sub HandleGraphEvent()
            Dim hr As Integer = 0
            Dim evCode As EventCode
            Dim evParam1 As Integer
            Dim evParam2 As Integer
            If Me.MediaEventEx Is Nothing Then
                Return
            End If
            While Me.MediaEventEx.GetEvent(evCode, evParam1, evParam2, 0) = 0
                hr = Me.MediaEventEx.FreeEventParams(evCode, evParam1, evParam2)
                DsError.ThrowExceptionForHR(hr)

            End While
        End Sub

        Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
            If disposing Then
                closeinterfaces()
            End If
            MyBase.Dispose(disposing)
        End Sub
        Public Sub closeinterfaces()
            If Not (Me.MediaControl Is Nothing) Then
                Me.MediaControl.StopWhenReady()
            End If

            Me.CurrentState = PlayState.Stopped

            If Not (Me.MediaEventEx Is Nothing) Then
                Me.MediaEventEx.SetNotifyWindow(IntPtr.Zero, WM_GRAPHNOTIFY, IntPtr.Zero)
            End If

            If Not (Me.VideoWindow Is Nothing) Then
                Me.VideoWindow.put_Visible(OABool.False)
                Me.VideoWindow.put_Owner(IntPtr.Zero)
            End If

            If Not (rot Is Nothing) Then
                rot.Dispose()
                rot = Nothing
            End If

            Marshal.ReleaseComObject(Me.MediaControl) : Me.MediaControl = Nothing
            Marshal.ReleaseComObject(Me.MediaEventEx) : Me.MediaEventEx = Nothing
            Marshal.ReleaseComObject(Me.VideoWindow) : Me.VideoWindow = Nothing
            Marshal.ReleaseComObject(Me.GraphBuilder) : Me.GraphBuilder = Nothing
            Marshal.ReleaseComObject(Me.CaptureGraphBuilder) : Me.CaptureGraphBuilder = Nothing

        End Sub

        Private Sub Form1_Resize1(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize
            If Me.WindowState = FormWindowState.Minimized Then
                ChangePreviewState(False)
            End If
            If Me.WindowState = FormWindowState.Normal Then
                ChangePreviewState(True)
            End If
            ResizeVideoWindow()
        End Sub
        Public Sub ChangePreviewState(ByVal showVideo As Boolean)
            Dim hr As Integer = 0
            If Me.MediaControl Is Nothing Then
                Debug.WriteLine("MediaControl is nothing")
                Return
            End If
            If showVideo = True Then
                If Not (Me.CurrentState = PlayState.Running) Then
                    Debug.WriteLine("Start previewing video data")
                    hr = Me.MediaControl.Run
                    Me.CurrentState = PlayState.Running
                End If
            Else
                Debug.WriteLine("Stop previewing video data")
                hr = Me.MediaControl.StopWhenReady
                Me.CurrentState = PlayState.Stopped
            End If
        End Sub
        Public Sub ResizeVideoWindow()
            If Not (Me.VideoWindow Is Nothing) Then
                Me.VideoWindow.SetWindowPosition(0, 0, Me.Width, Me.ClientSize.Height)
            End If
        End Sub
    End Class
End Namespace

Any help would be appreciated.