Re: compression parameters on re-save jpeg

[Sven Neumann]

 When I load a jpeg image (e.g. to turn it 90drg) which compression parameters
 got 
 it saved with using save (Ctrl-S). I assume the original once are not recorded
 in the image,
 so how could I be shure that the quality is perserved.

The quality can not be preserved since JPEG is a lossy format and will
always degenerate the image on each subsequent save. If I remember 
correctly, GIMP does indeed store the compression parameters with your 
image. If you use the "Save As" function you have the possibility to 
check and change the parameters. 


Salut, Sven

Re: compression parameters on re-save jpeg

[Marc Lehmann]

On Fri, Jun 09, 2000 at 12:24:35PM +0200, Andreas Haack [EMAIL PROTECTED] wrote:
 it saved with using save (Ctrl-S). I assume the original once are not recorded
 in the image,
 so how could I be shure that the quality is perserved.

Just do not use JPEG ;) In general it is impossible to do what you want,
especially if some other program wrote the JPEG.

In practise you should save the JPEG in a quality very near the original
quality. It is also possible to guess the quality (my "judge" program does
something similar to this, for example), but it is very difficult. (Also,
one might not want to "judge" the quality of the image, but the quality of
the quantization factor instead).

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