[Gimp-developer] jpeg quality factor.

[gg at catking.net]

On Sat, 07 Jul 2007 11:23:55 +0200, Tor Lillqvist <tml at iki.fi> wrote:

> rcook at pcug.org.au writes:
>  > Here if I can do say 10 re-saves at 85% quality, it produces no
>  > discernible changes in picture quality.
>
> Presumably you also re-load the image you just saved each time?
>
> --tml
>

If you save the same data it will compress identically and the will be no  
more loss than the original compression. It's not the fact of pressing the  
save button that causes the loss of data it is the discrete cosine  
transform that appoximates the image as a large number of cosine functions.

If you make some changes you will lose a bit of quality on every save. How  
much depends on the nature of those changes.

gg