[MacPerl] comparing image files

[Rich Morin <rdm@cfcl.com>]

I'm interested in comparing image files, in order to find duplicates.
Because there are several thousand files, an NxN comparison is out of
the question.  Also, it is quite possible that some of the images may
have been resized or tweaked in other manners, so the comparison will
not be an exact one.  Finally, the images are mostly in JPEG format,
so they will have to be expanded into pixels before any comparison
can be done.

Here is some pseudo-perl that describes my current thinking:

   Walk tree of JPEG files, using File::Find
     Expand file image to pixmap form
     create a signature ($key) for image
     $tag{$key}++ if ($got{$key} ne '');
     $got{$key}   .= "  $File::Find::name ($key)\n";

   foreach $key (keys(%tag)) { push (@val, $got{$key}); }

   foreach $val (sort(@val)) { printf("%s\n", $val); }

Actually, the code above assumes that the signatures will be exact,
which is unlikely...  Anyway, I'm looking for suggestions on:

   *  expanding JPEGs into pixmaps
   *  signature creation
   *  non-exact signature comparisons

Ideas, anyone?

-r
--
Rich Morin:          rdm@cfcl.com, +1 650-873-7841, http://www.ptf.com/~rdm
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