[Image-SIG] Manipulating JPEGs w/out decompressing?

Smurf smurf at smurf.noris.de
Mon Jan 26 20:44:34 EST 2004


Chris Cogdon:
> >them by swapping the coefficients in the individual blocks as well as
> >the blocks themselves, and probably some other minor stuff.
> I don't think it's as simple as that.
> Firstly, even within the 8x8 cells, you need to rotate THAT as an 
> element, meaning the association within the surrounding pixels is 
> changed.
That's what I believe I said.

> So... while I think it's a great goal, I believe doing editing beyond 
> simply adding or subtracting profile information cannot be achieved 
> without decoding then encoding again.
jpegtools can do it, so it's evidently possible.
(I didn't say it was easy. :- / )

Matthias Urlichs     |     noris network AG     |     http://smurf.noris.de/

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