This sample shows how to display the incoming video from a webcam in a picturebox. It will display a list of avaliable devices and allow you to capture an image and save it. It uses the CapCreateCaptureWindow api. This sample requires a listbox lstDevices, picturebox picCapture, 4 buttons (btnStart, btnSave, btnStop, btnInfo), and a Save File Dialog sfdImage.
Imports System.Runtime.InteropServices
Public Class Form1
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
Public Const WM_CAP_GET_STATUS As Integer = WM_CAP + 54
Public Const WM_CAP_DLG_VIDEOFORMAT As Integer = WM_CAP + 41
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
Private DeviceID As Integer = 0 ' Current device ID
Private 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, _
ByRef lParam As CAPSTATUS) As Boolean
Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Boolean, _
ByRef lParam As Integer) As Boolean
Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, _
ByRef lParam As Integer) As Boolean
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
Structure POINTAPI
Dim x As Integer
Dim y As Integer
End Structure
Public Structure CAPSTATUS
Dim uiImageWidth As Integer '// Width of the image
Dim uiImageHeight As Integer '// Height of the image
Dim fLiveWindow As Integer '// Now Previewing video?
Dim fOverlayWindow As Integer '// Now Overlaying video?
Dim fScale As Integer '// Scale image to client?
Dim ptScroll As POINTAPI '// Scroll position
Dim fUsingDefaultPalette As Integer '// Using default driver palette?
Dim fAudioHardware As Integer '// Audio hardware present?
Dim fCapFileExists As Integer '// Does capture file exist?
Dim dwCurrentVideoFrame As Integer '// # of video frames cap'td
Dim dwCurrentVideoFramesDropped As Integer '// # of video frames dropped
Dim dwCurrentWaveSamples As Integer '// # of wave samples cap'td
Dim dwCurrentTimeElapsedMS As Integer '// Elapsed capture duration
Dim hPalCurrent As Integer '// Current palette in use
Dim fCapturingNow As Integer '// Capture in progress?
Dim dwReturn As Integer '// Error value after any operation
Dim wNumVideoAllocated As Integer '// Actual number of video buffers
Dim wNumAudioAllocated As Integer '// Actual number of audio buffers
End Structure
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
Me.AutoScrollMinSize = New Size(100, 100)
btnStop.Enabled = False
btnSave.Enabled = False
btnInfo.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 Short = 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 += CType(1, Short)
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(DeviceID.ToString, WS_VISIBLE Or WS_CHILD, 0, 0, 1280, _
1024, picCapture.Handle.ToInt32, 0)
'
' Connect to device
'
If SendMessage(hHwnd, WM_CAP_DRIVER_CONNECT, DeviceID, 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
btnInfo.Enabled = True
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
DeviceID = lstDevices.SelectedIndex
OpenPreviewWindow()
Dim bReturn As Boolean
Dim s As CAPSTATUS
bReturn = SendMessage(hHwnd, WM_CAP_GET_STATUS, Marshal.SizeOf(s), s)
Debug.WriteLine(String.Format("Video Size {0} x {1}", s.uiImageWidth, s.uiImageHeight))
End Sub
Private Sub ClosePreviewWindow()
'
' Disconnect from device
'
SendMessage(hHwnd, WM_CAP_DRIVER_DISCONNECT, DeviceID, 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
btnInfo.Enabled = False
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 Bitmap
'
' 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)), Bitmap)
picCapture.Image = bmap
ClosePreviewWindow()
btnSave.Enabled = False
btnStop.Enabled = False
btnStart.Enabled = True
btnInfo.Enabled = False
Trace.Assert(Not (bmap Is Nothing))
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
Private Sub btnInfo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnInfo.Click
SendMessage(hHwnd, WM_CAP_DLG_VIDEOFORMAT, 0&, 0&)
End Sub
End Class
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