[fitswcs] VO standard for JPEG with WCS

[Frank Valdes]

FWIW one approach for the science community would be wrapping the  
JPEG file with FITS as in the "foreign file" encapsulation method.  I  
use this to write PNG files to a FITS file for ingestion into an  
archive that primarily uses FITS headers for metadata.  One nice  
thing about this is FITS multi-extension so that, in my example, the  
FITS container has two PNGs for a postage stamp and for a larger  
"science-like" version.  The "foreign file" conventions are  
documented and could easily move to a standard if desired.

OTOH, if a graphic format already provides a blob where an  
specialized stuff can be stored that won't break the functions of  
standard software (photo software for instance) then I would  
certainly agree that if the astronomical community could agree on a  
standard way to store a WCS (probably just FITS "cards") this would  
be good.  Any such agreement I would suggest should happen under the  
auspices of the astronomy community FITS committees and mechanisms.

My $0.02 worth,
Frank Valdes

On Jan 17, 2008, at 8:27 AM, William Pence wrote:

> FYI, there was a brief email exchange on the VO email lists
> (apps at ivoa.net and dal at ivao.net) concerning encoding WCS  
> information in
> JPEG images.  Copies of the current thread of 3 messages are shown
> below.  If you are interested in this topic, you can subscribe to the
> email lists at http://www.ivoa.net/forum/
>
> Bill Pence
>
> Pierre Fernique wrote:
>>
>>
>> Hi all,
>>
>> Some projects are using JPEG images with WCS keywords or FITS header
>> memorized into a JPEG comment segment (DSS colour images from  
>> MAST, SDSS
>> JPEG images, Aladin JPEG images,...).
>>
>> Unfortunately these methods are not compatible, not documented and  
>> seems
>> to evolve.
>>
>> Could we have a kind of VO standard related to this point ?
>>
>> One suggestion would be to put the FITS header - or a portion of the
>> FITS header - into a JPEG comment segment (starting with FF FE)  
>> directly
>> in ASCII but with the possibility for wrapping each line by a CR  
>> instead
>> of keeping the 80 character FITS justification. By this way, a simple
>> "strings" command (or equivalent) allows to display immediately the
>> metadata. Another advantage, and not the least, is to have the
>> possibility for keeping all the FITS metadata.
>>
>> Good idea ? Bad idea ? Other suggestions ?
>>
>> Regards
>> Pierre Fernique
>
> Arnold Rots wrote:
>> Since it can be specified in STC XML, one could include an STC
>> ObsDataLocation element. That way we use a VO standard.
>>
>>   - Arnold
>>
>> --------------------------------------------------------------------- 
>> -----
>> Arnold H. Rots                                Chandra X-ray  
>> Science Center
>> Smithsonian Astrophysical Observatory                tel:  +1 617  
>> 496 7701
>> 60 Garden Street, MS 67                              fax:  +1 617  
>> 495 7356
>> Cambridge, MA 02138                              
>> arots at head.cfa.harvard.edu
>> USA                                     http://hea-www.harvard.edu/ 
>> ~arots/
>> --------------------------------------------------------------------- 
>> -----
>
> Ray Plante wrote:
>> Hey Pierre,
>>
>> A standard for tagging JPEGs with metadata for outreach purposes  
>> is in
>> the works, driven by a US-European collaboration.  It's current  
>> form is
>> in the IVOA is a Note, "Astronomical Outreach Imagery Metadata  
>> Tags for
>> the Virtual Observatory"
>> (http://www.ivoa.net/Documents/latest/AOIMetadata.html).
>> The contact people in Europe are Lars Lindberg Christensen and Markus
>> Dolensky, and in the US, Robert Hurt.  They are in the process of
>> revising the document and getting ready for a comment process for  
>> both
>> the outreach community and the IVOA.
>>
>> cheers,
>> Ray
>
> -- 
> ____________________________________________________________________
> Dr. William Pence                       William.Pence at nasa.gov
> NASA/GSFC Code 662       HEASARC        +1-301-286-4599 (voice)
> Greenbelt MD 20771                      +1-301-286-1684 (fax)
>
>
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