1997.05.23 06:12 "CCITT Grp 4 - uncompressed data", by Robert Pelcak

1997.05.23 19:56 "Re: CCITT Grp 4 - uncompressed data", by Frank D. Cringle

"Fax4Decode:... Uncompressed data (not supported)... ". Inspection of the source code in tif_fax3.c showed that:

  1. The encode/decode algorithm has been completely re-done, to one "derived from Frank Cringle's viewfax";
  2. The current code most certainly does not support the uncompressed data option for CCITT Group 4.

Why is this option no longer supported?

Because I was too lazy to include it in my code. I guess Sam thought the advantages of the new code for the normal (compressed) case outweighed this omission. Also, uncompressed T.6 mode is somewhat deprecated by the TIFF Spec (p.53):

  Uncompressed mode is not well-specified and many applications
  discourage its usage, prefering alternatives such as different
  compressions on a segment-by-segment (strip or tile) basis, or by
  simply leaving the image uncompressed...

That is not much consolation if you have such images to deal with, though.

Is there anything that we can do so that we can handle CCITT Group 4 graphics using that option?

Use an old libtiff version or add the functionality to the current version.

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