OMG, at last!

That's what I was trying to say since the beginning.
I know jpeg is a lossy format (I knew that for at least ten years). I 
know, and always knew, that it has generational degradation.
I didn't know that PS compression scale doesn't follow the jpeg 
specification. Thanks for the information, I know it now.
Despite the scale thing, most of the people know that jpeg loses image 
I don't know the internal structure of a jpeg file, but please don't 
tell me. I'm talking from the user perspective here.

What I didn't know (and wouldn't expect) is that Gimp will destroy my 
pictures without warning me.
And that's exactly what I get.
I have a picture taken at 95, open it and save it, and it ends up at 85. 
Why is that?
I'm a professional designer. I'm not using jpeg for professional work. I 
used tiff and PSD with PS and now I'm using xcf.
I know that. Don't try to explain me how to work, because I know it.
But I'm a person too, not just a designer, and use to take some family 
pictures. The camera that I use (an old Nikon Coolpix 800) saves in jpeg 
and tiff format. Tiff format is huge and slow, jpeg is more handy.
During a weekend with my family, I took a couple of pictures. Some of 
them were under-exposed.
It doesn't matter. I open them, tweak the curves a little, and save 
them, for instance.
Nobody will be using "other formats for intermediate work" in such case. 
It's a single tweaking.
This is a VERY COMMON practice. And if you think that is perfectly 
normal that the program recompresses the images without warning, let me 
tell you that you're wrong. As others already said: One expects that a 
"fine" quality picture from a camera will be saved with a similar 
quality. Not a half.
If gimp can't read the quality setting from the image, then it should 
display the export settings EVERY TIME you save a jpeg image as jpeg.
Destroyed image data is not a expectable "feature".

Sven wrote:

> Why should any application do what you suggest? If you open a JPEG file
> and save it again as JPEG, then the original quality factor is
> completely irrelevant. You are doing a lossy operation, there is no way
> to save the file with the same quality again.

Yes, but if you had a great looking photo you don't expect to have a 
heavily compressed image with lots of artifacts, bad edges and color 
You expect a similar quality.
If once the image is decoded the quality factor doesn't matter anymore, 
why don't you display the export options when saving? It would make 
sense to do that.
The user wants control over the exporting process, but for now Gimp is 
taking the decision for him.

Sven wrote:
> Due to the way file plug-ins are implemented in GIMP, it is not trivial
> to do this. But you can easily work around it by assigning Ctrl-S to
> "Save As". Then you will always be prompted with the dialog asking you
> for the save parameters.

The problem is not me. I know the problem now and I won't use CTRL+S for 
mi jpegs anymore.
I'm concerned about lots of users that will learn that too in the hard 
way, destroying some irreplaceable images.

There seems to be a big gap between developers and users here. 
Developers base their opinions on technical issues but seem to forget 
the problems that pop up in the everyday use. I'm a user, I plan to keep 
using Gimp everyday, and this jpeg exporting issue is (from the user 
perspective) definitively a PROBLEM.
>From the user perspective, the way that Gimp processes the jpeg images 
now isn't tha obvious.
I had to start this discussion here to find out how it works, and now I 
have it clear. But what happens with the thousands of users out there?

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