On Sun, 08 Jul 2007 12:10:30 +0200, Øyvind Kolås <[EMAIL PROTECTED]> wrote:

> But a full decode/encode/decode cycle of JPEG / DV /
> MJPEG etc will accumulate more and more errors/artifacts. This
> accumulated error would be smaller with a higher default quality
> though.
>  /Øyvind K.
> --

Obviously what Guillermo is doing is fine as an exercise but his first  
save should be to a non lossy format or if his first save is his final  
save at least use Save As to get the full dlg and save it to the same name  
if that's what he wants.

Personally I would always keep any original image so even a 'first save =  
last save' would get a new name and hence go through the dlg with the  
quality option.

You clearly know more about the detail of this than I do but isn't there a  
direct one-to-one mapping once the original compression is done?

Any deviation from that must be errors in the decoding, so is what you  
posted a symptom of continual rounding errors in the decoding altering the  
image each time?

Then the growing artifacts are a result of the limited colour resolution  
of 8 bits per channel used by gimp.


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