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1-34 Guide to Using Page Description Languages
Creating the necessary PostScript CCITT Group 3 and 4
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.
Print performance related to image printing
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.