[Gimp-user] Re: Altering comment in jpegs

[Guillermo S. Romero / Familia Romero]

[EMAIL PROTECTED] (2001-04-05 at 1127.35 -0400):
> I don't think that you would loose quality in the jpeg by reopening it
> in the gimp, as long as the quality slider in the jpeg save dialog was
> set at 100%.

No, I finally understood the concepts of JPEG, it does a colorspace
conversion, so any time the data is passed to RGB and back, you loose
data, even if it is only due number rounding.

All this computer rounding is the reason why high level works are done
in float or big integers, cos you add error each time an operation is
performed, so the bigger the number space, less visible problems in
the end.

Any real life example are 20 and 24 bit sound systems (sometimes even
more, and in floating point) and 16 bit per channel images (Gimp Film,
IIRC) or even more. From time to time there is somebody asking the
list for help about processing > 8 bit images for a scientific job.

> There might be an easy script for it, however.

The best way would be to only touch the message data, not the image
data. I do not remember any tools for this, I remember tools for
recompressing PNG, for example. Maybe in http://freshmeat.net/ there
is something.

GSR
 
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