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Introduction
1-10
MC68322 USER’S MANUAL
MOTOROLA
In addition to width and height dimensions, an unpacked bitmap also possesses an attribute
known as the bitmap warp, which is the distance between the beginning of each consecutive
scanline. The bitmap warp is the value used to obtain Y dimension movement within the
bitmap. For example, to move from one pixel to a pixel in the same column, but in the next
lower scanline, simply add the bitmap warp to the current position in memory. A packed
bitmap also has a bitmap warp that is equal to the width of the bitmap.
1.4.3 Banding
Banding is a process in which the page to be printed is constructed in a series of partial page
images or bands. To better accommodate banding, the MC68322 allows the page image to
be represented in an intermediate form. In this intermediate form, the page image is
represented by a series of graphic orders, which are collectively called a display list and are
maintained in memory.
The PDL or PCL emulator firmware running on the core generates the display list before the
print engine begins the actual printing process. The RGP executes the graphic orders in the
display list to build the bitmapped image in bands as the print engine is started. Generally,
band
n+1 is being constructed while band n is being output to the print engine.
1.4.4 Halftoning
Halftoning involves applying a pattern or halftone screen to a data transfer to modify its
appearance. Halftone screens are used to produce shades of gray in a monochrome printing
environment such as printing presses, dot matrix printers, or laser printers. Halftone screens
are commonly seen in newspapers because that is where photographs with levels of gray
are represented with a medium that only allows black and white. Halftone screens are
repetitive in both the X and Y dimensions of a bitmap array. For example, to perform
shading, a 10101010 pattern might be applied to the even scanlines and a 01010101 pattern
to the odd scanlines.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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