Xerox DocuPrint Network Printer Series Guide Manual page 55

POSTSCRIPT
Figure 2-9. Image orientation mismatch B
Printer's paper
orientation
Output
Image
A
Slow
Slow
Rotated
A
A
Fast
Output Output
without rotation with rotation
The scan order of an image relative to the content of the image is not
important. It is important that the scan order of the image in the
desired orientation is relative to the scan order of the page.
There are circumstances during which a transformation cannot be
avoided by any ordering of image data (such as when the image
sides are not parallel to the sides of the paper, or when the image is
skewed), but for many cases, you can avoid a rotation by ensuring
that the data in the image is in the correct order.
Ensuring optimum image data order is complicated by the fact that
the rotations are not tied to the use of the rotate operator in a
PostScript program, or to implied rotations in the image-to-user
space transformation. The transformations in the figures above are
automatically performed on data by DocuPrint NPS when required as
part of rendering. The transformations specified in PostScript are part
of a specification of the desired position of an image in terms of the
default user coordinate system.
The following example shows the choice of row or column to describe
an arbitrary one-dimensional slice of an image that depends on the
viewpoint.
XEROX DOCUPRINT NPS GUIDE TO USING PAGE DESCRIPTION LANGUAGES 2-29