AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2000.01.29 01:15 "tiff2ps: G4 compression in PostScript]", by Paul Kaiser
[...]
2000.01.29 19:37 "Re: tiff2ps: G4 compression in PostScript]", by Paul Kaiser
2000.01.29 19:59 "Re: tiff2ps: G4 compression in PostScript]", by Helge Blischke
[...]

2000.01.29 19:59 "Re: tiff2ps: G4 compression in PostScript]", by Helge Blischke

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..."

But see the 3rd edition of the Red Book (or the 2017 supplement, I think). It describes the additional optional dictionary operand to the LZE filters containign the predictor value - a feature that is present since language level 2 but has missed to be documented in the 2nd edition of the Red Book. And I have processed lots of LZW compressed TIFF files using pure PostScript code using the LZWDecode filter and never had any errors.

Perhaps these filter shortcomings is why these filters are all "optional" in Level 3 implementations of PostScript rendering engines... They're Quite

The 3rd edition of the Red Book states that only the _Encode_ filters (short of the NullEncode filter) are optional; all _deconding_ filters are mandatory for every implementation that claims to be conformant to the spec.

Helge

H.Blischke@srz-berlin.de
H.Blischke@srz-berlin.com
H.Blischke@acm.org