On Fri, 30 May 2003, Chip Griffin <[log in to unmask]> wrote:

>>> Seems very complex. I am a little more leery of such a direct
>>> manipulation.
>>
>> Which begs the question why apparently indirect manipulation is less
>> leer-inducing in some folk--is it because of the power of
>> dissociation, i.e. one doesn't believe/fear one is meddling with a
>> file's data fork because one doesn't directly observe it being meddled
>> with, despite the fact that that is the known outcome (assuming
>> meddlesome success)?
>
>I am, as I suspect most non-experts are, a little hesitant to utilize
>byte-tweaking technology. A time tested program such as GC or the
>Finder doing the tweaking is fine. Writing an AppleScript to tweak
>bytes is uncomfortable territory. Like it or not, that's the way it is.

You're wise to be wary of undue complexity.  I tried to make it as
pared-back/basic as possible.

Whether I like it or not is immaterial; it's your project that
remains incomplete.  When you tested my non-expert script on some
(duplicate) JPEG files on your machine, did you find any for which it
didn't work?  Lots?  I didn't actually write it to be a finished
script--after all, I don't even know what you want to do with these
JPEG comments: add, alter, or delete them.  My thinking was simply to
show that a JFIF appears to be a relatively simple file structure,
one that even a non-expert like me can hash up.  I didn't expect you
to trust me to know what I was doing & use my method (in fact I added
explicit warnings to the contrary), I was simply trying to show that
it wouldn't be that hard for you to work out your own, more reliable
method.  Given the added complication of 'Exif' JPEGs, one might need
to alter one's script to ignore those, perhaps simply by checking the
first 7-10 characters of the files.

You haven't answered my earlier question whether Edit JFIF Comment
actually works under OSX or not.  If it does--& I happened to read
somewhere on the web that JPEGView runs very well in Classic, so I
can't see why Edit JFIF Comment wouldn't--then presumably that's one
possibility, & slowness be blowed if it gets the job done.  I'm
fairly confident it'd be faster than doing it all manually via GC's
UI menu, but feel free to prove me wrong on that, amongst other
things.  The other suggestion someone else made was to use Perl (or
was it Unix?--I can't recall), & if my memory hasn't failed
completely they seemed to suggest that there was a module already
written available on the web--i.e. you'd be able to blame someone
else if it failed, rather than have to wear it all yourself. <shrug>
Your images will all be backed-up to another storage device before
you do any experimenting, right?

>> I'm making no promises that I've properly understood the JPEG file
>> structure--there's probably an official definition available somewhere
>> on the web.
>
>That's exactly the point. It's more mysterious and arcane ...

Uh-huh.  So it'd be better if I'd've lied & said I knew exactly what
I was doing?

"Yes dahljnk, those earrjngs really sujt you."

P.S.  Chip, I presume you've tried searching the web for "jpeg
comments"?  There's a whole lot of stuff for PCs (do you happen to
have access to one of those?), & if one adds 'mac' to one's search
there's Image Info: <http://www.kanzu.com/imageinfo.html> (US$25),
which may or may not do what you want. <shrug>  Also possibly
relevant: <http://www.sentex.net/~mwandel/jhead/>

Selected from Ambrose Bierce's "Devil's Dictionary":
FIDELITY, n. -- A virtue peculiar to those who are about to be betrayed.