User Manual and Operating Guide
PostScript
Guide to Using Page Description Languages 1-35
Typical CCITT G3/G4 images have the fast scan direction along
the short edge of the paper and DocuPrint images along the long
edge of the paper. Therefore, in most cases, it is necessary to
perform an image rotation of 90 degrees on the CCITT G3/G4
data.
It is beneficial to create and to store CCITT G3/G4 images with
optimal scaling and rotation values for the target printer. These
CCITT G3/G4 images, of reasonable compression ratios,
typically print at or near rated printer speed.
Scan order and rotation
A scanned or sampled image is defined as a rectangular array of
sample values, each representing some color. In a PostScript
program, such an image is represented by a sequence of sample
values obtained by scanning the image rectangle in row or
column order.
For any image, there are eight such sequences (four scan origin
possibilities, with either a row or a column order choice for each).
Any of these sequences may be used in a PostScript program as
long as the image-to-user coordinate transformation matrix is
prepared correctly.
Purpose
There is one sequence in each case that enables the fastest
processing on DocuPrint NPS/IPS. You should know why there is
a difference in speed depending on the order chosen, and how to
choose the optimum order.
The laser scans the image area in a specific order relative to the
paper to produce the output image. For DocuPrint, the fast laser
scan direction is parallel to the long edge of the paper, and the
slow laser scan direction is parallel to the short edge of the
paper. The fast scan direction is in the direction of increasing y
coordinates and the slow scan direction is in the direction of
increasing x coordinates in the PostScript default user space,
with the y axis corresponding to the long edge of the paper.
Refer to the Adobe
PostScript Language Reference Manual
for
more information.