[kwlug-disc] Image Comparison

Chris Irwin chris at chrisirwin.ca
Fri Aug 14 15:09:37 EDT 2009


On Fri, 2009-08-14 at 09:17 -0400, Richard Weait wrote:
> On Thu, Aug 13, 2009 at 2:54 PM, Chris Irwin<chris at chrisirwin.ca> wrote:
> > (Sorry if this doesn't thread properly. I use IMAP via gmail and it
> > doesn't echo my own mail back to me, so I can't actually reply to myself
> > on-list.)
> 
> Looks okay here. ;-)
> 
> > I've got a bit of an update on my progress.
> 
> > On Tue, 2009-08-11 at 20:32 -0400, Chris Irwin wrote:
> >> Does anybody know of any way of mass comparing jpeg files by a image
> >> content rather than a file sum or name? I've got two sets of several
> >> thousand images I need to sort through. Basically I want to find unique
> >> files in directories A & B, deleting duplicates from B.
> >
> > Imagemagick has a utility called 'compare' that will take two images as
> > input, and output a third image illustrating the difference (it seems
> > to create a composite and overlay in red where they don't match).
> 
> [Fascinating Imagemagick results clipped.]
> > I've now got something I can use in a script. Thanks to those who
> > emailed me off-list with suggestions :)
> 
> That is pretty neat stuff, Chris.  Khalid's earlier post got me
> thinking, "Why not use exif time / date / camera info as a clue that
> two images came from the same source image?"  This way you can locate
> and store sanely the original photo and the resized version, or the
> original and the one that crops out Crazy uncle Richard....  Exif data
> may find photos that are closely related but that vary wildly in pixel
> count.

Some of the photos were resized improperly and do not contain any EXIF
data. Most photos have the exif data intact, but F-spot currently has a
pretty nasty bug that affected me:

https://bugs.edge.launchpad.net/ubuntu/+source/f-spot/+bug/175191

Oops.

-- 
Chris Irwin <chris at chrisirwin.ca>
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