CORRECTION: LZW in PDF (Was: FW: Unisys Launches Massive Ripoff of the Web)

[Dov Isaacs <isaacs@xxxxxxxxx>]

ALL:

Correction to my previous posting! The change in Acrobat to 
eliminate LZW compression came with Acrobat 4. LZW was still an
option in Acrobat 3!

(Please try to remember that to those in Adobe, Acrobat 4 has
been with us much longer than with you!)

As such, if you specifically requested LZW compression in
Acrobat 3 or earlier for images and you have images in your PDF
file, you then have PDF with LZW. If you requested "automatic"
compression of images, you may or may not have LZW, depending
on whether (1) the document has images and (2) the actual image
content.

Also, note that I am not a lawyer!

If you want to "fix" old PDF files and replace LZW compression
with ZIP, you have several options:

(1) Recreate the old PDF file from their sources, PostScript or
otherwise. This is probably the least palatable for anyone!

(2) Recreate the old PDF file by opening the PDF file in Acrobat 4
and "printing" PostScript to Acrobat Distiller. This obviously will
lose internal links.

(3) Quite Software's "Quite a Box of Tricks" plugin for Acrobat
allows you to change compression either by image or globally within a
document. I tried this on an old PDF document quite successfully.
There may be other sources of similar software.

I am personally not in a position to guess as to whether, how, and/or if
Unisys intends to globally enforce its interpretation of its patents on
LZW compression. I suspect, FWIW, that this is NOT a problem comparable
to Y2K in terms of immediate legal concern to most users. Again, I am not
a lawyer.

         - Dov


At 8/30/99 02:03 PM , Jeremy H. Griffith wrote:
>On Mon, 30 Aug 1999 13:29:09 -0700, Dov Isaacs <isaacs@Adobe.COM> wrote:
>
> >Adobe ran into this Unisys LZW issue several years ago. Even though we
> >site licensed it, Unisys was raising issues about anyone receiving content
> >with LZW compression used in our products.
> >
> >As such, Acrobat 3 and Acrobat 4 do not use LZW compression in CREATING
> >PDF files. The options include JPEG and ZIP for color and grayscale; 
> >CITT Group 3, CITT Group 4, ZIP, and run length encoding for single bit
> >bitmaps.
> >
> >PDF files generated with recent versions of Adobe Acrobat 4 have no
> >reason to be concerned about Unisys' licensing gambits.
>
>Thank you, Dov!  It's a relief to know that Acrobat 3 and 4 PDFs are
>guaranteed to be safe.  <g>  
>
>I still have some real old ones around, that may have been made with 
>original Acrobat or Acrobat 2.  Are they also safe?  Is there any good 
>way to check them and make sure?  I'm not sure if I even still have the 
>files I made them from on anything I can read.  (Think 5.25" floppy. ;-)
>
>Thanks again for settling this point!
>
>-- Jeremy H. Griffith, at Omni Systems Inc.


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