[fitsbits] Re: Reading floating point FITS files

[Mark Calabretta]

On Wed 2003/11/19 16:05:24 -0000, Rob Seaman wrote
in a message to: fitsbits at donar.cv.nrao.edu

>somebody will actually use this feature.  Are we really ready to see
>FITS turned into some poor man's XML to be used only as a wrapper to
>provide access to somebody else's data format?

I agree, it's a silly idea.

>It might help if somebody could provide a use case for why this might be
>a requirement of some astronomical project.

I already did.  Look at http://antwrp.gsfc.nasa.gov/apod/ap020920.html. 
Does this image contain astrophysical content?  Yes, phenomenal.  Would
it work as a greyscale?  No.  Clearly the use of colour in this, and the
many other images like it that are starting to appear regularly, is more
than just aesthetic.  It effectively provides a way of visualizing a
third dimension in the data.  The particular use-case I suggested was to
overlay a celestial coordinate grid on it.  Try getting PhotoShop to do
that!

Here's another.  Consider a 4-D data cube: RA, DEC, FREQ, STOKES.
STOKES could be mapped to RGB as an alternate WCS and this 4-cube
visualized as a colour movie or other animation.

This thread started because John Green, a software developer, was
assigned the job of importing FITS files and innocently asked how to
extract the RGB components from floating point data.  Clearly someone is
interested!

However, import of FITS into general image display and manipulation
packages such as xv, photoshop, etc., while important, is not as
interesting for astronomy as software which understands the other FITS
concepts such as coordinate systems, data cubes, and so on.  There is no
shortage of these (kvis, aips++ viewer, etc.).  Once colour FITS has
been defined they will eventually get around to implementing it - it's
really not that hard (and if not, well there just wasn't a pressing
need, but no harm done).  

It's too bad we had to admit to John Green that FITS is colour-blind -
even worse if we have to admit that it's not considered a significant
shortcoming.

Mark Calabretta
ATNF