24-Bit DIBs Draw Very Slowly When Running on an 8514

Last reviewed: November 23, 1994
Article ID: Q82378

The information in this article applies to:

Microsoft Windows operating system versions 3.1, 3.11

SUMMARY

When you use the 8514 video driver included with the Microsoft Windows, a 24-bit DIB (device independent bitmap) draws slowly because of 24-bit to 8-bit color matching.

MORE INFORMATION

24-Bit DIBs paint or appear slow on machines configured for the 8514 driver, and it may appear as though the machine has stopped. Actually, the machine is merely color-matching every pixel in the DIB. The video driver calls into the GDI (graphical device interface) for each pixel. This process causes the GDI to search the current system palette, containing 256 color elements, for the closest matching color. This color value is then returned to the driver. The slowdown occurs with any operation that converts a 24-bit DIB to an 8-bit DIB.

KBCategory: kbother kbdisplay kbgraphic
KBSubcategory: win31 windrvr
Additional reference words: 3.10 3.11

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Last reviewed: November 23, 1994
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