User's Manual

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