On Wed 2003/11/12 15:55:04 -0000, Rob Seaman wrote
in a message to:

5) "true color" FITS requires three input files - each file represents
red, green or blue data.

WCS Paper I Sect. 5.4 admits "conventional coordinate types" and cites
CTYPEi values of 'COMPLEX' and 'STOKES'. Paper II also introduces
'CUBEFACE'.

Clearly 'RGB', 'CMYK', and possibly others (e.g. 'RYB', 'YIQ', 'HSI',
'HSV', 'HSB', 'HLS') would be useful additions - see
http://www.efg2.com/Lab/Library/Colo...tm#ColorSpaces.

Typically these would be used in conjunction with BITPIX = 8. Rather
than three input files you'd then have one multi-dimensional image with
an 'RGB' axis. This seems tidier to me.

The semantics should not be too hard to define ('RGB' = WCS coordinate
values red = 1, green = 2, blue = 3; pixel value ranges from 0.0 to 1.0,
etc.).

Seems to me that astronomy could do with something like this for storing
pretty pictures from HST, etc.

Mark Calabretta
ATNF