2001.08.20 16:17 "compressed tiffs", by Leslie Friesen

2001.08.22 20:13 "Re: compressed tiffs", by Niles Ritter

My twenty cents:

If you are developing software for writing TIFF, I strongly recommend using the "libtiff" package, available at www.libtiff.org. This site also contains the links to the TIFF 6.0 format specification, which describes the other standard TIFF compression schemes, and the Tiff Tech Notes (TTN's) on the JPEG scheme.

A lot depends on your client's requirements. Do they need the images to be highly portable, to be read on a variety of image-processing packages? Why did they specify TIFF? Was there a particular imaging or printing package that required it?

The most portable TIFF compression schemes are LZW and PackBits. Of these, only the PackBits compression can be implemented without a license; the LZW scheme is patented by IBM and Unisys, though that patent runs in in 2003, I've heard. The PackBits scheme is okay, but not quite as good as LZW. I think the Wang Imaging product can save TIFF using LZW (they paid the license fee). Photoshop can certainly do the job. ACDC might also be able to do it.

There is a freeware alternative to LZW called "zlib" (used in gzip) that can be hooked into the libtiff package. More and more imaging products support this, but again it depends on your sponsor. It is not part of the 6.0 spec, but is described in some tech notes.

CCITT (Fax 3 or 4) is designed for one-bit black and white images, so it is not useful for color.

JPEG-in-TIFF (Tech Note 2) gives you much higher (lossy) compression, but its support is limited outside of high-end (Adobe Photoshop) image editors.

One Caveat: Do not use the "interpretation" of the old TIFF 6.0 JPEG scheme in Wang Imaging. Files written in this bogus format may not be readable by other non-Wang based software or other platforms. Use the TTN#2 scheme if you need JPEG-in-TIFF.