Microsoft KB Archive/80670

= VB3 Copying Entire Screen into a Picture Box in Visual Basic =

Article ID: 80670

Article Last Modified on 11/18/2003

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APPLIES TO


 * Microsoft Visual Basic 1.0 Standard Edition
 * Microsoft Visual Basic 2.0 Standard Edition
 * Microsoft Visual Basic 3.0 Professional Edition

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This article was previously published under Q80670



SUMMARY
Using the Windows API call BitBlt, you can capture the entire Microsoft Windows screen and place the image into a Microsoft Visual Basic for Windows picture box.

First, get the handle to the desktop. Then use the desktop window handle to get the handle to the desktop's device context (hDC). Finally, use the Windows API call BitBlt to copy the screen into the Picture property of a Visual Basic for Windows picture box control.



Step-by-Step Example
 Start Visual Basic for Windows (VB.EXE). Form1 is created by default. Add a picture box (Picture1) to Form1.  Set the following properties:   Control    Property      Value --  Picture1   AutoRedraw    True Picture1  Visible       False

  Add the following code to your .BAS module: Type lrect left As Integer top As Integer right As Integer bottom As Integer End Type Declare Function GetDesktopWindow Lib &quot;user&quot; As Integer Declare Function GetDC Lib &quot;user&quot; (ByVal hWnd%) As Integer ' Enter the following Declare on one, single line: Declare Function BitBlt Lib &quot;GDI&quot; (ByVal hDestDC%, ByVal X%, ByVal Y%,     ByVal nWidth%, ByVal nHeight%, ByVal hSrcDC%, ByVal XSrc%,      ByVal YSrc%, ByVal dwRop&amp;) As Integer ' Enter the following Declare on one, single line: Declare Function ReleaseDC Lib &quot;User&quot;(ByVal hWnd As Integer, ByVal hDC     As Integer) As Integer Declare Sub GetWindowRect Lib &quot;User&quot; (ByVal hWnd%, lpRect As lrect) Global Const True = -1 'Comment out this line if using Visual Basic 3.0. Global Const False = 0 'Comment out this line if using Visual Basic 3.0. Global TwipsPerPixel As Single

  Add the following code to the Form1 Click event procedure: Sub Form_Click Call GrabScreen End Sub

Sub GrabScreen

Dim winSize As lrect

' Assign information of the source bitmap. ' Note that BitBlt requires coordinates in pixels. hwndSrc% = GetDesktopWindow hSrcDC% = GetDC(hwndSrc%) XSrc% = 0: YSrc% = 0 Call GetWindowRect(hwndSrc%, winSize) nWidth% = winSize.right            ' Units in pixels. nHeight% = winSize.bottom          ' Units in pixels.

' Assign informate of the destination bitmap. hDestDC% = Form1.Picture1.hDC x% = 0: Y% = 0

' Set global variable TwipsPerPixel and use to set ' picture box to same size as screen being grabbed. ' If picture box not the same size as picture being ' BitBlt'ed to it, it will chop off all that does not ' fit in the picture box. GetTwipsPerPixel Form1.Picture1.Top = 0 Form1.Picture1.Left = 0 Form1.Picture1.Width = (nWidth% + 1) * TwipsPerPixel Form1.Picture1.Height = (nHeight% + 1) * TwipsPerPixel

' Assign the value of the constant SRCOPYY to the Raster operation. dwRop&amp; = &HCC0020

' NOTE: function call must be on one line: Suc% = BitBlt(hDestDC%, x%, Y%, nWidth%, nHeight%,                   hSrcDC%, XSrc%, YSrc%, dwRop&amp;)

' Release the DeskTopWindow's hDC to Windows. ' Windows may hang if this is not done. Dmy% = ReleaseDC(hwndSrc%, hSrcDC%)

'Make the picture box visible. Form1.Picture1.Visible = True End Sub

Sub GetTwipsPerPixel ' Set a global variable with the Twips to Pixel ratio. Form1.ScaleMode = 3 NumPix = Form1.ScaleHeight Form1.ScaleMode = 1 TwipsPerPixel = Form1.ScaleHeight / NumPix End Sub

 Run the program. Click Form1.</li> Using the mouse, change the size of the form to see more of the picture box. With a little work, you can use this as a screen saver program.</li></ol>

Additional query words: print printer

Keywords: kbwndw kbcode KB80670

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