Q130805: Drawing to a Memory Bitmap for Faster Performance

Article: Q130805
Product(s): Microsoft Windows Software Development Kit
Version(s): 1.25,2000,3.1,3.5
Operating System(s): 
Keyword(s): kbfile kbgraphic kbOSWinNT350 kbOSWin2000 kbSDKWin32 kbOSWin95
Last Modified: 23-JUL-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
- Microsoft Win32 Application Programming Interface (API), used with:
   - Microsoft Windows 95 
   - Microsoft Windows NT Server version 3.5 
   - Microsoft Windows NT Workstation version 3.5 
   - Microsoft Win32s version 1.25 
- Microsoft Windows 2000 Advanced Server 
- Microsoft Windows 2000 Server 
- Microsoft Windows 2000 Professional 
-------------------------------------------------------------------------------

SUMMARY
=======

An application whose client area is a complex image can realize a performance
benefit from drawing to a memory bitmap. The complex, time consuming drawing
code need only be performed once - to initialize the offscreen bitmap. During
the handling of the WM_PAINT message, the only work that needs to be done is a
simple BitBlt from the memory bitmap to the screen.

Sample code demonstrating this technique is available in the Microsoft Dowload
Center. The MemDC sample code draws a complex pattern on its client area. A menu
option toggle allows the user to see the speed difference between using and not
using the offscreen bitmap.

MORE INFORMATION
================

The following file is available for download from the Microsoft Download
Center:

  Memdc.exe

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. Once posted, the file is housed on secure
servers that prevent any unauthorized changes to the file.

Additional query words: device context memory DC speed fast buffer kbfile kbgraphic

======================================================================
Keywords          : kbfile kbgraphic kbOSWinNT350 kbOSWin2000 kbSDKWin32 kbOSWin95 
Technology        : kbAudDeveloper kbSDKSearch kbWin32sSearch kbWin32API kbWinSDKSearch
Version           : :1.25,2000,3.1,3.5
Issue type        : kbinfo

=============================================================================

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.