A lot of document scanners last a long time. Now that
many people wish to scan in color, they use an older
scanner and color tiffs. Great! But what if the scanner used
the really old compression Level 6 which was replaced in 1995
with compression level 7?
In 1995 the Tiff Technical Note #2 said this about Code 6:
“This Technical Note describes serious problems
that have been found in TIFF 6.0's design for
embedding JPEG-compressed data in TIFF (Section 22 of the
TIFF 6.0 spec of 3 June 1992). A replacement TIFF/JPEG
specification is given. Some corrections to Section 21
are also given.
To permit TIFF implementations to continue to read
existing files, the 6.0 JPEG fields and tag values will
remain reserved indefinitely. However, TIFF writers are
strongly discouraged from using the 6.0 JPEG design.”
So, DMAC went looking for someone on the web who had
the old HP scanners and other old scanners which used code 6
compression and had updated the open source LIBTIFF code to
read what these old scanners produced.
After a half dozen or so tries of various renditions
of LIBTIFF, DMAC found an open source copy of LIBTIFF called
"LIBTIFF, Version 4.0.3 Copyright (c) 1988-1996 Sam Leffler
Copyright (c) 1991-1996 Silicon Graphics, Inc." which correctly
decoded the code 6 tiffs.
Then DMAC had to go through the differences between
its LIBTIFF and the version 4.0.4 LIBTIFF. The latest
version of Unibase by DMAC 8.7.7 now contains the results.
It allows Unibase by DMAC to correctly handle color tiffs
produced by the HP Scanners. Let DMAC know if you have a
code 6 tiff which does not work in the latest Unibase By DMAC.#