[Gimp-developer] jpeg quality factor.

[Roel Schroeven]

Sven Neumann schreef:
> Hi,
> 
> On Sun, 2007-07-08 at 14:53 +0200, gg at catking.net wrote:
> 
>> Does your reply indicate you take a "this feature not a bug" approach here  
>> and you think is the best way gimp should deal with this situation?
> 
> Indeed. When you open a JPEG file, then you have a decoded image. The
> settings that were used to encode it are irrelevant since encoding it
> again as a JPEG file would not yield the same image anyway. Thus it is
> better to use the default values. Since we will very soon allow the user
> to change these defaults, this should be the best way we can handle
> this.

Perhaps not a bug, but IMHO gimp's JPEG handling violates the principle 
of least surprise. I had a quick look at the source code and found out 
that the quality setting (and other parameters) are saved in a global 
variable jsvals, which is initialized with the default values (85 for 
the quality), but gets overwritten after "save as":

1. open a.jpg
2. save a.jpg
-> a.jpg is saved with the default quality, 85. Fine by me.
3. save a.jpg with "save as", with quality say 55
-> as expected it is saved with quality 55.
4. open b.jpg
5. save b.jpg
-> b.jpg is saved with quality 55 instead of 85!!

Wouldn't it be better if gimp acted in one of those two ways:
1. always save with the default quality, except when "save as" is used.
2. read the quality when loading a jpeg, and used that to save the image 
(if "save as" is not used).


-- 
If I have been able to see further, it was only because I stood
on the shoulders of giants.  -- Isaac Newton

Roel Schroeven