Very Computer

I'm looking for a program to compare pixel pictures.

I have thousends of files with pictures (jpeg, pnm, pcx and so on).

To find identical pictures I can cmp two files. They are identical,
if they compare bit by bit identically. Okay, that's very easy.

But in my view two pictures are even identical, if they show the same,
but with different resolutions (eg. 640x480 and 1024x768). The cmp
program will fail in that case, because they are not identical bit
by bit.

Does anybody know of a program, which analyzes the content of image
files and gives an answer, whether the pictures are the same or very
similar? It has something to do with pattern recognition.

I appreciate any hints and/or links.

Dieter Rohlfing

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Quote:> Does anybody know of a program, which analyzes the content of image files
> and gives an answer, whether the pictures are the same or very similar? It
> has something to do with pattern recognition.

I doubt you'll find something that does exactly what you want, but have you
considered using something like ImageMagick's "convert" program to generate,
say, 32x16 16-color thumbnails of all of your pictures, then use "cmp" to
check for similarities?
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Kirk Strauser
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Actually once I wrote such a program, but I lost it eons ago.
It was a short perl script which used convert.

I removed the outer 15 percent of the picture (so any borders were
lost), resized them to something like 8x8 and 2 colors, converted
to a common format (xpm I think), and I compared those images.
Surprisingly many similar images were found, but some was not,
and there were also a couple of false positives.

It did not perform perfectly, but it was pretty good compared
to the time and effort I invested into it.

If the OP knows a little about programming, then he might go
along this path and the whole thing can be done in a very
short time.

Vilmos

Thanks to Kirk and Vilmos for their replies.

Quote:>> I doubt you'll find something that does exactly what you want, but have you
>> considered using something like ImageMagick's "convert" program to generate,
>> say, 32x16 16-color thumbnails of all of your pictures, then use "cmp" to
>> check for similarities?

>I removed the outer 15 percent of the picture (so any borders were
>lost), resized them to something like 8x8 and 2 colors, converted
>to a common format (xpm I think), and I compared those images.
>Surprisingly many similar images were found, but some was not,
>and there were also a couple of false positives.

I think, your proposals bring me a lot closer to my goal. I do not expect
to find a 100% solution. A hit ratio of about 90% is very good for me.

Thanks again and have a nice day.

Dieter Rohlfing

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