On Thu, Feb 17, 2005 at 06:02:31PM +0200, Alexander Rabtchevich <[EMAIL 
PROTECTED]> wrote:
> Could it be done via additional menu item: open for the lossless 
> transformations with only few operations active? The operation itself 
> has sense for digital images with portrait orientation. It would be nice 
> to store the original images without data loss but with corrected 
> orientation.

I think it makes very little sense to put this into the gimp. The extra work
is IMHO just not worth it, a specialized extra application would be more

Or a plug-in. The number of (useful, lossless) operations that can be done
on jpegs is very limited.

> By the way, I'm just curious, is it possible to apply different jpeg 
> settings to the different parts of an image?

Yes, you can vary quantizazion factors, but i don't think the jpeg library
can handle that. The best you can do with respect to such tricks is
to use scan scripts to achieve some effects, for example, the image
at URL<http://kaya.schmorp.de/sofia/p1010043.jpg> has the monochrome
parts first which has the effect of first showing the grayscale image on
slow-enough connections.

> mean if the jpg image haven't undergo transformations affected the whole 
> image, the unaffected parts of the image could be saved as the original 
> compressed data without recompression (at least beyond adjacent points). 
> These pixels could be obtained by the simple comparison with the 
> original file.

That would be easy iff the underlying jpeg library supports it, and could
be limited to the jpeg plug-in. However, if you only use the ijg jpeg
library and take care of not changing the quantization factors you will
see that the pixels will already not change, i.e. there will be losless

So there is probably little demand for that. It would be far more useful
to have a way of knowing the quality the file was saved with (by the ijg
library) so it can be saved with the same quantizazion factor again, if
possible (i.e. as long as you use the same library to compres/decompress
the file).

                The choice of a
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