Image formats: JPEG vs. GIF (x Delta-l)

[Mike Dallwitz]

                                                                 31 March 1995

> From: "Consaul, Laurie" <LCONSAUL at mus-nature.ca>
> To: Mike Dallwitz
>
> I have [put all the image files] into .gif format so far, because I
> like the looks of them more than the looks of the .jpg files that alchemy
> produces, even when I use -j70 or -j100 (I also like the speed at which the
> .gif files open).
>
> Do you see any problem with my using .gif format as the standard; that is, I
> had heard a rumor that CompuServe was considering levying a charge for use
> of .gifs on the Internet. Have you heard any more on that?

JPEG files should look better than GIF files. If they look bad, it's probably
because you are viewing them in a 256-colour mode in Windows. Try them with a
32K- or 16M-colour mode. You should be able to use a fairly low quality factor
for your distributed images (as opposed to your archive copies, which should
really be TIFF anyway). Try experimenting with very low quality factors, e.g.
-j5. This will give you a feel for the kind of artifacts that are introduced,
and will help you to choose a quality factor which gives sufficiently good
results. Nevertheless, the fact that they don't look good in 256 colours, and
are slower to decompress, may be sufficient reasons not to use them.

It is Unisys, not CompuServe, which holds a patent on the compression method
used in GIF files. I think there will be little effect on users; it is up to
program developers to license the method if necessary.

Mike Dallwitz                                  Internet md at ento.csiro.au
CSIRO Division of Entomology                   Fax +61 6 246 4000
GPO Box 1700, Canberra ACT 2601, Australia     Phone +61 6 246 4075