[TAG] JPEG de-duplication

[Ben Okopnik]

On Mon, Jul 26, 2010 at 06:40:33AM +0530, Kapil Hari Paranjape wrote:
> Hello,
> 
> On Sun, 25 Jul 2010, Neil Youngman wrote:
> > Initial research suggests that ImageMagick can produce a "signature", which is 
> > a SHA256 checksum of the image data. I believe that this would be suitable 
> > for identifying identical images, on which the tags have been altered. 
> 
> Quoting Glenn Randers-Pehrson (he of libpng fame):
> (ref http://studio.imagemagick.org/pipermail/magick-users/2003-March/007964.html)
> 
>  Two images with identical pixel data, even if stored in different
>  formats, will produce the same signature.  It is the SHA digest
>  computed over the pixels in a canonical form.
> 
> So "imagemagick -identify | grep signature" can indeed be used to
> check whether two images are pixel for pixel identical.

Is there an actual "imagemagick" program, or is it some util from the IM
suite? I don't have an "imagemagick" on my system, despite having the
package installed.


-- 
* Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *