[filmscanners] Re: JPEG Lossless mirror?

[TonySleep@halftone.co.uk]

On Fri, 8 Feb 2002 08:54:22 -0000  Mark Otway (mark@otway.com) wrote:

> I know the encoding only takes place when the image is saved in PS (as
> opposed to when it's manipulated). But since the act of re-encoding
> results in some data loss, if I can perform these simple tranformations
> (flip) without doing so then it's obviously preferable.

Convert to TIFF, flip, save as JPEG shouldn't leave you with a worse file
than when you started. But I'm not convinced merely flipping the JPEG would
either. Re-encoding *unchanged* data at the same compression setting gives
no additional loss. The question is whether flipping constitutes changing,
and I think it probably doesn't, but I don't know the JPEG spec well enough
to be sure. I am sure someone will.

Regards

Tony Sleep
http://www.halftone.co.uk - Online portfolio & exhibit; + film scanner info
& comparisons
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