Creating The Necessary Postscript Ccitt Group 3 And 4; Print Performance Related To Image Printing; Scan Order And Rotation - Xerox DocuPrint Network Printer Series Guide Manual

Creating the necessary PostScript CCITT Group 3 and 4

Print performance related to image printing

Scan order and rotation

XEROX DOCUPRINT NPS GUIDE TO USING PAGE DESCRIPTION LANGUAGES
You can embed an image that is compressed to CCITT group 4
specifications in the PostScript. You need to add several standard
PostScript statements before the embedded image to provide the
image parameters, and to properly use the FaxDecode filter.
Images use the PostScript image, imagemask, and filter
(CCITTFaxDecode filter) operators. Refer to the Adobe PostScript
Language Reference Manual for the proper syntax, specifically the
sections on the image and imagemask operators, the FaxDecode
filter, and transformation matrixes.
The source parameter of the CCITTFaxDecode filter operator
should be set to currentfile, and the bit/sample parameter of the
image operator should be 1 (for a binary image) because this
method of submission uses an embedded CCITT compressed
image. Either form of the image and imagemask operators can be
used; however, DocuPrint does not support any functionality in the
dictionary form that exceeds the functionality available through the
non-dictionary form of the operators.
Printing speed for CCITT G3/G4 documents is determined largely by
the decompression and imaging time. The decompression time is
correlated with the compression ratio (better compression means
less time). The imaging time is correlated with the kind of scaling and
rotation performed. Consequently, printing speed is dependent on
the document characteristics.
Optimal performance for CCITT G3/G4 printing is obtained with a 1-
to-1 scaling (for example, 300 dpi input resolution) and 0 degree
rotation. DocuPrint software is optimized to provide good
performance for the most frequently employed resolutions and
rotations. For example: resolutions of 200 dpi [fax]; 240 dpi
[IBM,etc.]; 400 dpi [extended fine fax]; and rotations of 0, 90, 180, or
270 degrees. Arbitrary scaling and/or rotation may impact
performance.
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.
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.
POSTSCRIPT
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