Well, here's my 2 cents on image formats in MIME/HTML:
For HTML, the popular formats are those formats built-in to the
graphical browsers. All currently support image/gif and many support
image/jpeg. I don't believe most other formats are built-in, although
some subsets of the TIFF standard can be viewed by helpers.
Currently most MIME clients seem to be built on the "attachment"
model, so all that matters is what helpers are available. Both image/jpeg
and image/gif are common, and some subsets of the TIFF standard are
Unisys's LZW patent is going to discourage use of GIF (as well as the
most common TIFF compression type), although this may take a while to
have effect. Due to GIF's popularity, it might be worth it to pay the
blood money to Unisys in the short term, if you can stomach doing so.
You definitely want to support image/jpeg. It is the best common
format for continuous tone images. It is also going to be the only
image format listed in the inital set of formats in the new MIME/Media
Types standard RFC. The IJG has a good public implementation at
<ftp://ftp.uu.net/graphics/jpeg/>. JPEG is mostly unsuitable for
images with fewer than 256 colors, and for line drawings.
I suggest you take a close look at the PNG image format, which I
believe has a good shot at replacing GIF as well as the common uses of
TIFF. See <http://sunsite.unc.edu/~boutell/png.html>. It is probably
the best lossless format around, although I don't know if it's been
implemented anywhere yet.
If you decide not to go with GIF, you might consider offering the TIFF
subset documented in RFC 1314
<http://andrew2.andrew.cmu.edu/rfc/rfc1314.html> for B&W images since
that is likely to be more useful in the short term than PNG. Also,
*baseline* TIFF 6.0 (which doesn't include LZW compression) is a
relatively portable subset.
Chris Newman <chrisn+(_at_)cmu(_dot_)edu>,