Answering Jeffery Jonas' question regarding huge PostScript files
resulting from using ctrans to generate PostScript from CELL ARRAYs
in a CGM.
The problem
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The problem here is that the graphcap structure (and PostScript is
a graphcap device) is not designed to interface with a hardware raster
capability. So, what is done for CELL ARRAYs in PostScript translation
is use a filled area for each individual cell in the CELL ARRAY. We
have long recognized that this is a very unsatisfactory solution, for
more reasons than the huge file sizes. The huge file sizes result from
the fact that, for each cell in the GGM CELL ARRAY, ctrans produces about
70 bytes of PostScript code for the coodinate points and color information
for each filled area. Since PostScript is ASCII, the coordinates are
represented as ASCII strings. So, in the case you were discussing of
a 360 x 180 CELL ARRAY, the translation to PostScript would produce about
4.5mb of PostScript for each of your CELL ARRAYs. Not good.
Help is on the way
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In version 4.0 of our package we have implemented a direct PostScript
output capability (B&W or color, portrait or landscape mode, PS or EPS or
EPSI) via GKS worksations. This will by-pass any ctrans conversion from
CGM to PostScript and produce PostScript directly. Also, CELL ARRAYs
are converted into PostScript images or color images (as appropriate),
thus obviating the need for simulation with filled areas. The 4.5mb of
output you were getting before will now be reduced to about 400kb (for
a full color image). Plus, the PostScript interpretation will be ten
times faster. Version 4.0 is due out by September (really! - we have sent
the codes off to cut the CD).
-- Fred Clare
NCAR Graphics Group
This archive was generated by hypermail 2b29 : Wed Jun 28 2000 - 09:40:25 MDT