Subject: IMAGE extension

From: [email-masked]
Date: Mon, 22 Jun 92 15:16:14 -0400

> To my mind, the extension name IMAGE is *deceptively* simple.  It
> implies something that just isn't necessarily true, i.e. that the
> extension contains a picture.

It doesn't imply that to me.  I suppose you are right that people in
other fields might be confused by the terminology but I think FITS should
be oriented towards astronomy.  In any case, I don't see any problem with
generalizing the concept of "image" (or "data image") to mean something
more complex than a picture.
 
> Are we going to have to have another extension, which is exactly the same
> except that XTENSION='SPECTRUM'?

A simple spectrum is a one dimensional image.  (there are also 2 and 3
dimensional spectra).  The proposed IMAGE extension could be used to
store spectra.
 
> There are, however, people who do think that FITS is only for images,
                                                                ^^^^^^
you mean pictures...

> and who are surprised when they discover that it doesn't include
> support for those features which are common for standard raster image
> formats like GIF, TIFF, etc., e.g. embedded color tables, or RGB color
> separation.  I've seen this confusion in people both on the
> (alt.)sci.astro.fits newsgroup, and in support personnel who have been
> working with us in developing hardware and software for astronomical
> observations.

FITS doesn't have to try to be all things to all people - I don't think
it would be successful it if did.  It was developed for astronomical
data, and the terminology should be oriented towards astronomy.  In current
astronomical use, "image" refers to a complex object (N-dimensional data
array with associated header etc.).  The terms array and picture refer
to simpler things.

This issue was discussed at both the European FITS meeting last May, and
again at the WGAS.  At the European meeting no one objected to the name
"IMAGE" for this extension, and in fact most people there preferred the
term.  The issue wasn't discussed explicitly at the WGAS meeting; if I
recall correctly the IMAGE extension was brought up for discussion and
there were no objections raised.

Doug Tody
[email-masked]