
Graphic Operations
12-2
MC68322 USER’S MANUAL
MOTOROLA
Frame—A frame bitmap is a two dimensional array of pixels that is generally a subset
of some larger bitmap array (the width and warp are identical). For example, a frame
bitmap could describe the bounding box of a character. To better illustrate this
difference, suppose a rectangle is transferred to a bitmap, both the warp of the bitmap
and the width of the rectangle being transferred must be specified. When transferring a
rectangle to a frame bitmap, the warp is the width of the rectangle being transferred.
Operations that involve transferring pixels to frame bit maps are particularly useful
when a small rectangle of a larger image must be saved for future reference. The frame
bitmap is the smallest possible storage means for the rectangle because the scanlines
are packed in memory. The end of one scanline and the beginning of the next have no
unused bits between them.
Halftone—A halftone bitmap is a special type of bitmap because it is automatically
replicated in both the horizontal and vertical directions. It is intended to hold a pattern
that is repetitively applied to data being transferred from a source bitmap to a
destination bitmap, thus causing a change in the appearance of the data.
12.2 GRAPHIC OPERANDS
Up to three operands are used when composing the print image—source, destination, and
halftone. The source operand is typically located in a frame or unexpanded bitmap, the
destination operand in a banded or unbanded bitmap, and the halftone operand in a halftone
bitmap. These operands are represented by a specific 1-byte constant value, which is listed
in Table 12-1.
These five constant values can be combined using Boolean arithmetic computations to yield
a 1-byte Boolean code that corresponds to a specific transfer effect. See Section 12.4
Boolean Codes for more information.
Table 12-1. Graphic Operation Data
Operand Constant Values
CONSTANTS
BINARY CODING
Zero
00000000
One
11111111
Destination
10101010
Source
11001100
Halftone
11110000
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