On Thu, 20 Sep 2007 05:23:13 +0200 (CEST), "Alchemie foto\\grafiche" <[EMAIL 
PROTECTED]> wrote:
> Raphael Quinet wrote
> _" I do not
> want to say too much about that because I do not want to give too many
> ideas to the crooks, but let's say that the way some things are split
> or ordered in the JPEG file is usually different between digital
> cameras and image editing software."_
> Well i too don't want give ideas to crooks, but i want say that there is no 
> way to demonstrate that a imagine is faked,
> You can only demonstrate that is a fake if some mistake were done, if not, 
> simply there is no way,

Well, the point is that most people do make mistakes.

We can even play a little game if you want: give me the URL of some JPEG
image that claims to come directly from a digital camera.  I bet that I
can tell you immediately if it was modified by some other program.  And
with a bit of luck, I could even tell you which program has modified it
even if the EXIF metadata is not included in the file or has been
modified.  Note that the removal of the EXIF block is already a hint
that the image has been modified, since almost all digital cameras
include EXIF blocks in all their images.

If you have the latest GIMP from SVN (soon to be 2.4-rc3), you can also
try to run the small test program in plug-ins/jpeg/jpegqual and it may
tell you some things that you did not expect about some of your JPEG
files.  Note that this tool is still under development, but you can
already do some interesting things with it.

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