[fitsbits] start of Public Comment Period on compressed FITS image and tables

[Erik Bray]

On 06/25/2015 04:37 AM, Mark Taylor wrote:
> On Wed, 24 Jun 2015, Mandel, Eric wrote:
>
>>>
>>> How interesting.  I'm not sure if your experience argues for or
>>> against the incorporation of tile compression in the standard.
>>
>>
>> For me as a developer, tiled compression already is part of the standard:
>> the very first email we got after announcing release 1 of JS9 (October
>> 2014) was a complaint that it did not  handle rice-compressed tiled
>> images.  I eventually came to the conclusion that cfitsio *was* the
>> practical standard, at least for anyone trying to write software for the
>> community at large. I know Bill Joye has spent a lot of time implementing
>> tiled compression in DS9 (which does not use cfitsio), just because of
>> widespread demand.
>
> I don't deal much with images, but interestingly, I have never
> had complaints or requests concerning use of tile-compressed FITS
> tables in STIL/STILTS/TOPCAT.  That suggests that tile compression
> for table data is much less used than for image data.  Can anybody
> comment on whether that's the case?

I have never encountered compressed tables in the wild.  If I had to guess, this 
is in part because the documentation for the convention was not easy to come by 
until recently.  It was not available on the registered FITS conventions 
website, or at least, I never noticed it.  Nobody has every asked for support in 
PyFITS or Astropy.

Tile-compressed images, however, I would consider an essential part of the 
standard regardless whether it's classified as a "mere convention".  Not 
supporting it renders a significant number of FITS files effectively unreadable. 
  (I'd have no problem with supporting compressed tables either if there was 
significant demand for it, but I haven't seen that...)

Erik