Intel 815 manual BLT Programming Examples, Pattern Fill -- a Very Simple BLT

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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6.3.BLT Programming Examples

6.3.1.Pattern Fill -- A Very Simple BLT

In this example, a rectangular area on the screen is to be filled with a color pattern stored as pattern data in off-screen memory. The screen has a resolution of 1024x768 and the graphics system has been set to a color depth of 8 bits per pixel.

Figure 19. On-Screen Destination for Example Pattern Fill BLT

		63	128, 128	0
(0, 0)	(1023, 0)			20080h
128, 128	191, 128			20088h
				20090h	On
				20098h
					128th
				200A0h	Scan
Rectangular				200A8h	Line
Area to be Filled	Scan Lines 128 Through 191			200B0h
(Destination)				200B8h
			(191, 128)
128, 191	191, 191		(128, 191)
				2FC80h
				2FC88h
				2FC90h	On
				2FC98h
					191th
				2FCA0h	Scan
Note: Drawing is not to scale				2FCA8h	Line
				2FCB0h
(0, 767)	(1023, 767)			2FCB8h
			(191, 191)
				b_blt20.vsd

As shown in the figure above, the rectangular area to be filled has its upper left-hand corner at coordinates (128, 128) and its lower right-hand corner at coordinates (191, 191). These coordinates define a rectangle covering 64 scan lines, each scan line’s worth of which is 64 pixels in length — in other words, an array of 64x64 pixels. Presuming that the pixel at coordinates (0, 0) corresponds to the byte at address 00h in the frame buffer memory, the pixel at (128, 128) corresponds to the byte at address 20080h.

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