Chapter 2 Graphics Tutorial
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Next, the SFNT (Select current FoNT by typeface) on line 5 selects Helvetica Bold, a
scalable (outline) font as the current font and scales the font to a height of 54 points. Use
of SFNT and other font selection commands are explained more fully in PRESCRIBE
Commands Command Reference.
The PMZP command on line 6 moves the cursor to the point that is 72 points (1 inch)
from the left edge limit and 2 inches from the top edge limit.
The CPTH command on line 7 constructs a path using the outline of the characters in the
string xyz. The cursor is moved to the end of the string.
Finally, the FILL command fills the path with the selected pattern, and PAGE prints out
the page.
Raster Graphics
While the graphics commands of the standard and path modes draw shapes such as lines,
circles, and boxes, raster graphics commands specify individual dots to draw images.
The dot resolution is selectable from 75 to 300 dots per inch for all models; and 600-dpi
models have two more choices of 200 dpi and 600 dpi. Lower resolutions give a rougher
appearance, but require less raster data for an image of a given size.
Raster graphics are limited in size only by the dimensions of the paper, and in complex-
ity only by the dot resolution.
Raster Data Compression Formats
PRESCRIBE supports raster data in three formats: uncompressed raster data, run-length
encoded raster data, or raster data encoded in tagged image file format (TIFF).
Uncompressed Raster Data
Uncompressed raster data consists of a simple, unencoded bit image consisting of binary
data in which 1 bit represent black dots and 0 bit represent white dots. With this format,
each dot line is divided into 8-dot segments. The settings of dots in each segment are
controlled by the bit values of each byte of raster data. Bit 7 (the highest-order bit in the
first byte of data received) corresponds to the first dot in the dot line, bit 0 corresponds to
the eighth dot, and so forth.
Run-length Encoded Raster Data
With run-length encoding, raster data is encoded in pairs of bytes. The first byte of each
pair indicates a repetition count for the second byte. A value of zero in the first byte indi-
cates that the pattern represented in second byte is not repeated; that is, it occurs only
once. A value of 1 in the first byte indicates that the pattern is repeated once, and so
forth. The first byte can specify any repetition count from 0 to 255.
Raster Data in Tagged Image File Format
The tagged image file format (TIFF) combines features of the uncompressed format and
run-length encoding. A control byte determines whether the following byte or bytes of
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General
Weight and Dimensions
