Microsoft KB Archive/130805

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Drawing to a Memory Bitmap for Faster Performance

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Q130805

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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

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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 Software Library. 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 files are 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

Issue type : kbinfo

Technology : kbAudDeveloper kbSDKSearch kbWin32sSearch kbWin32API kbWinSDKSearch