Message-ID: v03130300b4b7ee487663@[216.43.19.88]
To: tiff@olympiakos.com
Subject: tiff2ps: G4 compression in PostScript]
From: Paul Kaiser <buddy@effingham.net>
Date: Fri, 28 Jan 2000 19:15:33 -0600
In-Reply-To: <388E3DBE.5DBE@srz-berlin.de>
Sender: owner-tiff@olympiakos.com


I have been investigating the G4 compression issue intensely for the past week.

Adobe Acrobat will create a PDF using G4 compression for monochrome images
if so requested. Then, if you export that PDF as PostScript, the image
still retains G4 compression and uses the /CCITTFaxDecode filter in the
PostScript code.

I am therefore using such a PDF exported as PS to compare. The PDF/PS was
created from a bitmap TIF, and the same bitmap TIF with G4 compression is
then compared.

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!

Regards,
Paul Kaiser
GoodBuddy Software
http://www.goodbuddy.net



