Fwd: [fitswcs] VO standard for JPEG with WCS

Frank Valdes valdes at noao.edu
Thu Jan 17 07:59:36 PST 2008

I am not subscribed but I am taking Bill Pence's suggestion to  
contribute to the discussion.

Frank Valdes

From: Frank Valdes <valdes at noao.edu>
Date: January 17, 2008 8:51:00 AM MST
To: fitswcs <fitswcs at nrao.edu>
Subject: Re: [fitswcs] VO standard for JPEG with WCS

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
>> 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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