could any one explain me this code pls
Imports System.Runtime.InteropServices
Public Class Form1
Inherits System.Windows.Forms.Form
#Region " Windows Form Designer generated code "
Public Sub New()
MyBase.New()
'This call is required by the Windows Form Designer.
InitializeComponent()
'Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents picCapture As System.Windows.Forms.PictureBox
Friend WithEvents lstDevices As System.Windows.Forms.ListBox
Friend WithEvents lblDevice As System.Windows.Forms.Label
Friend WithEvents btnStart As System.Windows.Forms.Button
Friend WithEvents btnSave As System.Windows.Forms.Button
Friend WithEvents btnStop As System.Windows.Forms.Button
Friend WithEvents sfdImage As System.Windows.Forms.SaveFileDialog
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
Me.picCapture = New System.Windows.Forms.PictureBox()
Me.lstDevices = New System.Windows.Forms.ListBox()
Me.lblDevice = New System.Windows.Forms.Label()
Me.btnStart = New System.Windows.Forms.Button()
Me.btnSave = New System.Windows.Forms.Button()
Me.btnStop = New System.Windows.Forms.Button()
Me.sfdImage = New System.Windows.Forms.SaveFileDialog()
Me.SuspendLayout()
'
'picCapture
'
Me.picCapture.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D
Me.picCapture.Location = New System.Drawing.Point(208, 24)
Me.picCapture.Name = "picCapture"
Me.picCapture.Size = New System.Drawing.Size(256, 272)
Me.picCapture.TabIndex = 0
Me.picCapture.TabStop = False
'
'lstDevices
'
Me.lstDevices.Location = New System.Drawing.Point(8, 55)
Me.lstDevices.Name = "lstDevices"
Me.lstDevices.Size = New System.Drawing.Size(184, 238)
Me.lstDevices.TabIndex = 1
'
'lblDevice
'
Me.lblDevice.Location = New System.Drawing.Point(8, 32)
Me.lblDevice.Name = "lblDevice"
Me.lblDevice.Size = New System.Drawing.Size(184, 16)
Me.lblDevice.TabIndex = 2
Me.lblDevice.Text = "Available Devices"
Me.lblDevice.TextAlign = System.Drawing.ContentAlignment.TopCenter
'
'btnStart
'
Me.btnStart.Location = New System.Drawing.Point(20, 320)
Me.btnStart.Name = "btnStart"
Me.btnStart.Size = New System.Drawing.Size(112, 32)
Me.btnStart.TabIndex = 3
Me.btnStart.Text = "Start Preview"
'
'btnSave
'
Me.btnSave.Anchor = (System.Windows.Forms.AnchorStyles.Bottom Or System.Windows.Forms.AnchorStyles.Right)
Me.btnSave.Location = New System.Drawing.Point(348, 320)
Me.btnSave.Name = "btnSave"
Me.btnSave.Size = New System.Drawing.Size(112, 32)
Me.btnSave.TabIndex = 4
Me.btnSave.Text = "Save Image"
'
'btnStop
'
Me.btnStop.Location = New System.Drawing.Point(184, 320)
Me.btnStop.Name = "btnStop"
Me.btnStop.Size = New System.Drawing.Size(112, 32)
Me.btnStop.TabIndex = 5
Me.btnStop.Text = "Stop Preview"
'
'sfdImage
'
Me.sfdImage.FileName = "Webcam1"
Me.sfdImage.Filter = "Bitmap|*.bmp"
'
'Form1
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(480, 382)
Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.btnStop, Me.btnSave, Me.btnStart, Me.lblDevice, Me.lstDevices, Me.picCapture})
Me.Name = "Form1"
Me.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen
Me.Text = "Video Capture"
Me.ResumeLayout(False)
End Sub
#End Region
Const WM_CAP As Short = &H400S
Const WM_CAP_DRIVER_CONNECT As Integer = WM_CAP + 10
Const WM_CAP_DRIVER_DISCONNECT As Integer = WM_CAP + 11
Const WM_CAP_EDIT_COPY As Integer = WM_CAP + 30
Const WM_CAP_SET_PREVIEW As Integer = WM_CAP + 50
Const WM_CAP_SET_PREVIEWRATE As Integer = WM_CAP + 52
Const WM_CAP_SET_SCALE As Integer = WM_CAP + 53
Const WS_CHILD As Integer = &H40000000
Const WS_VISIBLE As Integer = &H10000000
Const SWP_NOMOVE As Short = &H2S
Const SWP_NOSIZE As Short = 1
Const SWP_NOZORDER As Short = &H4S
Const HWND_BOTTOM As Short = 1
Dim iDevice As Integer = 0 ' Current device ID
Dim hHwnd As Integer ' Handle to preview window
Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, _
<MarshalAs(UnmanagedType.AsAny)> ByVal lParam As Object) As Integer
Declare Function SetWindowPos Lib "user32" Alias "SetWindowPos" (ByVal hwnd As Integer, _
ByVal hWndInsertAfter As Integer, ByVal x As Integer, ByVal y As Integer, _
ByVal cx As Integer, ByVal cy As Integer, ByVal wFlags As Integer) As Integer
Declare Function DestroyWindow Lib "user32" (ByVal hndw As Integer) As Boolean
Declare Function capCreateCaptureWindowA Lib "avicap32.dll" _
(ByVal lpszWindowName As String, ByVal dwStyle As Integer, _
ByVal x As Integer, ByVal y As Integer, ByVal nWidth As Integer, _
ByVal nHeight As Short, ByVal hWndParent As Integer, _
ByVal nID As Integer) As Integer
Declare Function capGetDriverDescriptionA Lib "avicap32.dll" (ByVal wDriver As Short, _
ByVal lpszName As String, ByVal cbName As Integer, ByVal lpszVer As String, _
ByVal cbVer As Integer) As Boolean
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
LoadDeviceList()
If lstDevices.Items.Count > 0 Then
btnStart.Enabled = True
lstDevices.SelectedIndex = 0
btnStart.Enabled = True
Else
lstDevices.Items.Add("No Capture Device")
btnStart.Enabled = False
End If
btnStop.Enabled = False
btnSave.Enabled = False
picCapture.SizeMode = PictureBoxSizeMode.StretchImage
End Sub
Private Sub LoadDeviceList()
Dim strName As String = Space(100)
Dim strVer As String = Space(100)
Dim bReturn As Boolean
Dim x As Integer = 0
'
' Load name of all avialable devices into the lstDevices
'
Do
'
' Get Driver name and version
'
bReturn = capGetDriverDescriptionA(x, strName, 100, strVer, 100)
'
' If there was a device add device name to the list
'
If bReturn Then lstDevices.Items.Add(strName.Trim)
x += 1
Loop Until bReturn = False
End Sub
Private Sub OpenPreviewWindow()
Dim iHeight As Integer = picCapture.Height
Dim iWidth As Integer = picCapture.Width
'
' Open Preview window in picturebox
'
hHwnd = capCreateCaptureWindowA(iDevice, WS_VISIBLE Or WS_CHILD, 0, 0, 640, _
480, picCapture.Handle.ToInt32, 0)
'
' Connect to device
'
If SendMessage(hHwnd, WM_CAP_DRIVER_CONNECT, iDevice, 0) Then
'
'Set the preview scale
'
SendMessage(hHwnd, WM_CAP_SET_SCALE, True, 0)
'
'Set the preview rate in milliseconds
'
SendMessage(hHwnd, WM_CAP_SET_PREVIEWRATE, 66, 0)
'
'Start previewing the image from the camera
'
SendMessage(hHwnd, WM_CAP_SET_PREVIEW, True, 0)
'
' Resize window to fit in picturebox
'
SetWindowPos(hHwnd, HWND_BOTTOM, 0, 0, picCapture.Width, picCapture.Height, _
SWP_NOMOVE Or SWP_NOZORDER)
btnSave.Enabled = True
btnStop.Enabled = True
btnStart.Enabled = False
Else
'
' Error connecting to device close window
'
DestroyWindow(hHwnd)
btnSave.Enabled = False
End If
End Sub
Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.Click
iDevice = lstDevices.SelectedIndex
OpenPreviewWindow()
End Sub
Private Sub ClosePreviewWindow()
'
' Disconnect from device
'
SendMessage(hHwnd, WM_CAP_DRIVER_DISCONNECT, iDevice, 0)
'
' close window
'
DestroyWindow(hHwnd)
End Sub
Private Sub btnStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStop.Click
ClosePreviewWindow()
btnSave.Enabled = False
btnStart.Enabled = True
btnStop.Enabled = False
End Sub
Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
Dim data As IDataObject
Dim bmap As Image
'
' Copy image to clipboard
'
SendMessage(hHwnd, WM_CAP_EDIT_COPY, 0, 0)
'
' Get image from clipboard and convert it to a bitmap
'
data = Clipboard.GetDataObject()
If data.GetDataPresent(GetType(System.Drawing.Bitmap)) Then
bmap = CType(data.GetData(GetType(System.Drawing.Bitmap)), Image)
picCapture.Image = bmap
ClosePreviewWindow()
btnSave.Enabled = False
btnStop.Enabled = False
btnStart.Enabled = True
If sfdImage.ShowDialog = DialogResult.OK Then
bmap.Save(sfdImage.FileName, Imaging.ImageFormat.Bmp)
End If
End If
End Sub
Private Sub Form1_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
If btnStop.Enabled Then
ClosePreviewWindow()
End If
End Sub
End Class