[NBLUG/talk] Searching for near-identical photos?

[Aaron G]

http://www.cit.gu.edu.au/~anthony/graphics/imagick6/compare/

You might find that intresting... Its basicly just changing the color
hue where the pictures don't match.. so a picture with lots of color
chages, is gonna have a large amout of diff... etc..
I still think its impratical, sure it would be nice... but its not
something compuers would be good at(currently).
 -Aaron


Bill Kendrick wrote:

>On Sun, Nov 06, 2005 at 12:53:28PM -0800, Lincoln Peters wrote:
>  
>
>>Anyone know of a program that could tell me if two photos are nearly 
>>identical, even if they aren't 100% identical?  I ask because I'm working on 
>>a large collection of photos for a group at SSU, and I suspect that it 
>>contains several duplicates that differ only slightly (e.g. two copies of a 
>>printed photo that were scanned at different times, perhaps with different 
>>settings, or even with different scanners).
>>    
>>
>
>I did a quick Google search for "compare images linux", and one hit I got
>was a Linux.com article on how to use Image Magick:
>
>  http://applications.linux.com/article.pl?sid=05/03/29/1525217&tid=39&tid=49&tid=47
>
>One person's comment to the article was:
>
>  One of our firmware test developers found a scripted routine for
>  using ImageMagik to compare images. The script analyzed the images and
>  could find images that were similar without being exactly the
>  same. The degree of similarity could be roughly determined. This
>  allows for things like registration offset or slight color changes to
>  be tolerated whilst finding matching images.
>
>
>Seems sensible.  Reducing the image in various ways can help you find
>possible matches:
>
>  * Reduce the size of the image.
>    + This removes small differences in the picture, e.g. from JPEG artifacts
>    + This allows for matching two differently-sized scans of the same picture
>      (e.g., reduce a 1600x1200 and an 800x600 both down to 320x240, then
>      compare)
>
>  * Reduce the colors.
>    + Either posterize the image, or otherwise break it down to a very low
>      color palette (to allow for difference in color quality of scans),
>      or perhaps just switch to greyscale or even 1-bit black-and-white
>
>  * Crop!
>    + Take out borders
>
>  * Rotate a few degrees either direction...?
>
>
>This could all be batched somehow.  Along with the KDE image comparison
>front-end I mentioned in my last post (to someone else's follow-up),
>which I know very little about, I'd be surprised if there weren't at least
>a few other tools for doing this under Linux.  And I'd bet they're scriptable
>via Image Magick (or Gimp's non-GUI batch-mode).
>
>
>  
>
>>I think that GNUift might be able to do this, but I've never been able to get
>>it to work.
>>    
>>
>
>And I'll need to research that, cuz I've never heard of it. ;)
>
>  
>