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

[Mark Taylor]

On Wed, 24 Jun 2015, Mandel, Eric wrote:

> >
> > Yes the implementation of this proposed addition to the standard
> > is all there in CFITSIO, but that can't be used directly by
> > non-C-friendly languages such as java, javascript, and who knows
> > what future platforms might arise.  That means that for instance
> > browser-based FITS image viewers which currently can display any
> > legal FITS image would likely, following incorporation of this
> > convention to the standard, find themselves unable to deal with
> > some standard FITS image data if they are unable to afford
> 
> considerable extra implementation effort.
> 
> 
> For the record, this is not strictly true. The JS9 project (DS9 in the
> browser, see http://js9.si.edu) can read any FITS file (subject to browser
> memory limitations, along with my coding skills), because we implement FITS
> support by compiling cfitsio to optimized javascript using emscripten (
> http://kripken.github.io/emscripten-site/). One should be able to drag and
> drop any FITS data file onto the JS9 web site to display the image. In
> fact, there is a lot of work going on in the Web world to make C available
> inside the browser (cf. the latest developments at
> http://www.2ality.com/2015/06/web-assembly.html). So I think the Web world
> will be able to follow whatever FITS standards we agree on, so long as
> there are C implementations to support those standards.
> 
> But as Mark points out, it's a different question whether one wants to make
> the FITS standard so complicated that only a relatively few C/C++ library
> implementations can claim completeness. One big reason we moved to
> emscripten and cfitsio is that it was way too much work to implement tiled
> compression in the javascript FITS library we wrote for initial JS9
> implementation.

How interesting.  I'm not sure if your experience argues for or
against the incorporation of tile compression in the standard.

--
Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-9288776  http://www.star.bris.ac.uk/~mbt/