From kfm-devel  Wed Jan 16 22:33:33 2002
From: Bryce Nesbitt <bryce () obviously ! com>
Date: Wed, 16 Jan 2002 22:33:33 +0000
To: kfm-devel
Subject: Re: [rfe] .jpg & .gif comments (setting & viewing)
X-MARC-Message: https://marc.info/?l=kfm-devel&m=101122066918969

Rob Kaper wrote:
> 
> On Wed, Jan 16, 2002 at 10:53:54AM -0500, Bryce Nesbitt wrote:
> >       Comment:        Just before she was hit by
> >                       the truck.  Notice look of
> >                       horror on her face.
> >
> > By embedding the comment inside the .gif or .jpg, rather than a separate database
> > like most camera software uses, the comment won't get lost over time.
> 
> Ooh. Sounds more useful than all the "Created by Blurb" stuff image programs
> put there. Not sure how long comments can be.. if PHP can read this than
> that would make web archives uber easy.

64K enough for you?

       "The  JPEG  standard allows "comment" (COM) blocks to occur
       within a JPEG file.  Although the standard  doesn't  actu­
       ally  define what COM blocks are for, they are widely used
       to hold user-supplied text strings.   This  lets  you  add
       annotations,  titles, index terms, etc to your JPEG files,
       and later retrieve them as text.  COM blocks do not inter­
       fere  with the image stored in the JPEG file.  The maximum
       size of a COM block is 64K, but you can have  as  many  of
       them as you like in one JPEG file."

If KDE just treats these as utf-8 text comments, everthing should be just dandy.

			-Bryce


PS: See also http://www.sentex.net/~mwandel/jhead/ .  EXIF stores all the
camera settings, focal length, etc, in complicated and hard to parse form
that's poorly standardized.