[Gimp-developer] jpeg quality factor.

[Guillermo Espertino]

Owen:
> Interesting, what platform are you using?
>   
Ubuntu Linux (7.04) and Gimp 2.3.18

> Here if I can do say 10 re-saves at 85% quality, it produces no
> discernible changes in picture quality.
>
> In fact I have tried to prove that recompressing jpg pictures reduces the
> picture quality and got bored doing it at 85% (which btw is the Gimp
> default)
>   
I can't say the same. Today my wife uploaded a couple of photos to her 
flickr, and she noticed the same.
http://www.flickr.com/photos/superdd/738669627/
Se only opened the image from the camera, adjusted the curves, and 
scaled it down (BTW, the downscale code should do oversamplig by 
default. It always breaks a little the edges). Until she saved, the 
image quality was good.
Then she saved with CTRL+S, without changing the "quality" factor, and 
the picture turned out like that. Heavily compressed.

> Opinion.
> Y
> You should never work on a jpeg, take it in off your camera, save it as an
> xcf and when finished, recreate it as a jpeg if you want.
>   
Of course. I always do that. I use XCF (or PNG if the image is a single 
layer) for work.
But usually I take the pictures from my digital camera and make a quick 
levels and color adjustment, and that's when the problem pops up.
If you just want to adjust a bunch of pictures from your camera, it's 
not very handy to save the pictures as XCF. It takes more space and it's 
not a very popular format for viewers of other platforms.

Gez.