Q318188: HOW TO: Save The Contents Of Visual Basic Form To a DIB Section
Article: Q318188
Product(s): Microsoft Visual Basic for Windows
Version(s):
Operating System(s):
Keyword(s): kbBitmap kbGDI kbSDKPlatform kbSDKWin32 kbDSupport kbGrpDSGDI kbHOWTOmaster kbgdip
Last Modified: 28-MAR-2002
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, Version 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, Version 6.0
-------------------------------------------------------------------------------
IN THIS TASK
- SUMMARY
- Save the Client Area to a DIB Section
- Sample Code
- REFERENCES
SUMMARY
=======
This article demonstrates how to use the Graphics Device Interface (GDI)
application programming interface (API) to save the client area of a Visual
Basic form to a device-independent bitmap, known as a DIB section, that
applications can write to directly. A DIB section, which you can create by
calling the Windows API function CreateDIBSection(), allows device-independent
modification of the bits because you have access to a pointer to the location of
the bitmap's bit values.
Save the Client Area to a DIB Section
-------------------------------------
To save the client area of a Visual Basic form to a DIB section, follow these
steps:
1. Use the GetDC() GDI API call to create a device context for the Visual Basic
form window's client area.
2. Create a DIB section bitmap that is the same size as the Visual Basic form
window's client area.
3. Use the CreateCompatibleDC() GDI API call to create a memory device context
that is compatible with the Visual Basic form window's device context that
you created in step 1.
4. Use the SelectObject GDI API call to select the DIB section bitmap into the
memory device context.
5. Use a GDI API call, such as BitBlt() or StretchBlt() to transfer the image
from the form's device context to the memory device context.
Sample Code
-----------
To simplify the creation and use of DIB sections, a sample of code is available
that contains most of the functionality in a dynamic link library (DLL). For
additional information and to download this sample, click the article number
below to view the article in the Microsoft Knowledge Base:
Q186221 SAMPLE: DibSectn.exe Uses DIBSections in Win32
The sample code that follows uses this DLL to demonstrate the steps that are
listed earlier, and then calls DSStoreDIBSectionInBMPFile from the DLL to store
the DIB section to a file. You can use other functions in the DLL to make
changes to the DIB section that you create, or you can use GDI API calls.
Private Const SRCCOPY = &HCC0020 ' (DWORD) dest = source
Private Declare Function DSCreateDIBSection Lib "dibsectn.dll" ( _
ByVal dwX As Long, _
ByVal dwY As Long, _
ByVal wBits As Integer) _
As Long
Private Declare Function DSStoreDIBSectionInBMPFile Lib "dibsectn.dll" ( _
ByVal szFileName As String, _
ByVal hBitmap As Long) _
As Boolean
Private Declare Function StretchBlt Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, _
ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC _
As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal nSrcWidth As Long, _
ByVal nSrcHeight As Long, ByVal dwRop As Long) As Long
Private Declare Function GetDC Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function ReleaseDC Lib "user32" (ByVal hwnd As Long, _
ByVal hdc As Long) As Long
Private Declare Function CreateCompatibleDC Lib "gdi32" _
(ByVal hdc As Long) As Long
Private Declare Function DeleteDC Lib "gdi32" _
(ByVal hdc As Long) As Long
Private Declare Function SelectObject Lib "gdi32" _
(ByVal hdc As Long, ByVal hObject As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" _
(ByVal hObject As Long) As Long
Dim hdc As Long
Dim DibSection As Long
Dim hOldBitmap As Long
Dim hdcMem As Long
Dim Ret As Long
hdc = GetDC(Form1.hwnd)
hdcMem = CreateCompatibleDC(hdc)
' Call DSCreateDIBSection() from the DLL.
' You can use the desired BPP in the last parameter(for example, 24)
DibSection = DSCreateDIBSection(Form1.ScaleWidth, Form1.ScaleHeight, 24)
hOldBitmap = SelectObject(hdcMem, DibSection)
Ret = StretchBlt(hdcMem, 0, 0, Form1.ScaleWidth, _
Form1.ScaleHeight, hdc, 0, 0, Form1.ScaleWidth, _
Form1.ScaleHeight, SRCCOPY)
If Ret = 0 Then GoTo Error
hOldBitmap = SelectObject(hdcMem, hOldBitmap)
' Call DSStoreDIBSectionInBMPFile() from the DLL.
' Add error handling.
Ret = DSStoreDIBSectionInBMPFile("c:\test.bmp", DibSection)
If Ret = 0 Then GoTo Error
Ret = ReleaseDC(Form1.hwnd, hdc)
If Ret = 0 Then GoTo Error
Ret = DeleteDC(hdcMem)
If Ret = 0 Then GoTo Error
Ret = DeleteObject(DibSection)
If Ret = 0 Then GoTo Error
Error:
Debug.Print "Error" ' Add error handling here.
Success:
Debug.Print "Successful"
REFERENCES
==========
For more information, see the following MSDN Web site:
Windows DDK: Graphics Device Interface
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wmeother/graphcnt_1lpv.asp
Additional query words:
======================================================================
Keywords : kbBitmap kbGDI kbSDKPlatform kbSDKWin32 kbDSupport kbGrpDSGDI kbHOWTOmaster kbgdip
Version : :
Issue type : kbhowto
=============================================================================
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.
Copyright Microsoft Corporation 1986-2002.