On Mon, 09 Jul 2007 11:33:34 +0200, Tor Lillqvist <[EMAIL PROTECTED]> wrote:

> There are some scenarios in which blindly reusing the quality factor
> guesstimated from loading an image is not a good idea, even if the
> guesstimate is very accurate. (Which happens when the loaded image's
> quantization tables exactly match the JPEG standard's sample tables
> scaled in libjpeg's manner with said factor).
> I mean cases where the entire image contents has been replaced with a
> fresh (original quality) one. Or if the image has been scaled down. Or
> if some filter(s) that modifies all of the image substantially has
> been applied to the whole image. In cases like these it perhaps
> doesn't make sense to blindly re-use the original jpeg file's quality
> factor, but one should let the user decide.


OK let's ignore the repeated "blindly reusing" which presuposes this is a  
stupid thing to do.

If "the entire image contents has been replaced with a fresh (original  
quality) one" the user would presumably use saveAs. This seems rather an  
artificial case.

> Or if the image has been scaled down. Or
> if some filter(s) that modifies all of the image substantially has
> been applied to the whole image.

The current choice of jpeg_quality is still a more appropriate choice  
unless the user selects SaveAs.

Seriously guys , let's stop trying to secoond guess what the user "should"  
be doing and let him get on with it.

Again Gimp is a tool not a tutorial.

Let's concentrate on getting the tool to work propery rather than telling  
the user which hand he's supposed to wipe his backside with.


Tor, since you are looking at this, checkout this code. It's a shareware  
Delphi component for jpeg with sourse. Now it's years since I was in there  
but I bought it and used it for several years. I am pretty sure that it  
picks out jpeg_quality as one of the object properties when it decodes an  
image.

The delphi component is copyright shareware but it clearly states that the  
original IJG C code used is not a payable item. In any case seeing where  
the jpeg_quality comes from may well be useful.

http://www.mwasoftware.co.uk/index.php?option=com_content&task=view&id=4&Itemid=7

HTH.
/gg
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