AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2000.01.27 23:05 "latest libs - where?", by Paul Kaiser
2000.01.29 01:15 "tiff2ps: G4 compression in PostScript]", by Paul Kaiser
2000.01.29 09:48 "Re: tiff2ps: G4 compression in PostScript]", by Frank D. Cringle
2000.01.29 16:12 "Re: tiff2ps: G4 compression in PostScript]", by Paul Kaiser
2000.01.29 18:27 "Re: tiff2ps: G4 compression in PostScript]", by Helge Blischke
2000.02.01 21:38 "Re: tiff2ps: G4 compression in PostScript]", by Paul Kaiser
[...]

2000.01.29 09:48 "Re: tiff2ps: G4 compression in PostScript]", by Frank D. Cringle

When I compare the image data in the PS file to the actual image data from the G4 compressed TIF, they are VERY similar. However: -- Every now and then there is extra data in the TIF file compared to the data in the PS file.

I cannot figure out what extra data is written in the TIF file as compared to the bitmap data written in the PS file. The G4 specs from ITU specify that there may be some padding at the End of the transmission, but that doesn't seem to be the problem, as the observed differences are not all at the end of the file.

Anyway, If I figure anything out, I'll let the list know. I hope we can crack this one soon; it is very important to me!

Surely the most important property is that the results are identical *after* expansion. I don't remember whether the ITU specifies the encoder in such a way that there is exactly one legal encoding of a given image. In fact, I suspect it does not. An encoder can decide that part of a line can be most efficiently represented using uncompressed mode, for instance, whereas a simple encoder just "compresses" everything, which can turn out bigger in pathological cases.

--
Frank Cringle, fdc@cliwe.ping.de
voice: (+49 2304) 467101; fax: 943357