2000.01.29 19:37 "Re: tiff2ps: G4 compression in PostScript]", by Paul Kaiser
the differences between the Acrobat generated G4 compressed data and the original G4 TIFF
data are easily explained:
Well, you've proven that! Your explanation is excellent, on all counts.
While some of the things you point out can be overcome by using different options to the decoding filter in PostScript, others cannot (Boohoo!!)
Besides that, the T6 specification is somewhat unclear on the conditions where the
horizontal encoding mode should change.
>Well, good luck finding out whether Adobe has determined it >has to be "this way." If I am not mistaken, the problem with >DCTDecode filter in Adobe CPSI is this (from GS's gsjmorec.h):
Hmm. And this morning I tried an "LZW Compressed" image, but later found in the reference manual (PostScript Red Book) that "... this coding differs slightly from the one described in the TIFF 5.0 specification..."
It will be easier to create a program that decompresses a compressed TIFF image and builds a PostScript file from that. That way, our clients can still send compressed TIFF images to their service providers and get them output. We'll make the program available to the service providers.
Perhaps these filter shortcomings is why these filters are all "optional" in Level 3 implementations of PostScript rendering engines... They're Quite Impractical!