Bill Moran a écrit :
In response to FreeBSD <[EMAIL PROTECTED]>:

Andrew Gould a écrit :

On Tue, Sep 2, 2008 at 10:23 AM, FreeBSD <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote:

    Tom Marchand a écrit :

        Hash the images and compare the hashes.

         -------------- Original message ----------------------
        From: FreeBSD <[EMAIL PROTECTED]
        <mailto:[EMAIL PROTECTED]>>

            Hi everyone,

            I'm trying to determine if 2 jpeg images are identical. The
            images are screenshots taken with scrot at different times.
            The point is to know if the display is working correctly. I
            tried to use 'diff' but without success, probably because of
            the metadata included in the image. I also tried the
            'compare' command from imagemagick, but it produce an image
            containing the difference between the 2 images instead of
            telling me if both images are identical.

            So, my question is what are you using to determine if 2
            images are identical?

            I'm using FreeBSD 7.0 and I need to be able to script this
            comparaison for an integration in Nagios.

            Thank you,

            Martin


    I just tried it and it doesn't work. The hashes are different. I can't
    say that I'm surprised since 'diff' is "seeing" a difference between the
    two identical images.


    Thanks for the suggestion


Yes, there's a huge difference between testing differences in images and testing differences in files. What do you mean by "...know if the display is working correctly."?

Andrew
I want to determine if Mplayer is working correctly. The best way to be sure is to check if the display on the screen is changing. That's the purpose of the screenshots. The screenshots are taken by Nagios every 5 minutes and the new screenshot is compared with the preceding one. But, by now, it doesn't work because every tool we try is seeing a diffence between 2 identical images.

Can you put the screenshots into some other format?  As you mentioned,
the jpeg format includes metadata, which might include the creation
time and would cause every image to be unique from a filesystem view.
For example, I don't believe bitmaps include metadata, which would cause
them to be identical if the display were identical.


Thank you! It did the trick. I just converted the image from png (sorry it wasn't jpeg...) to bmp and it works with cmp. Even diff now recognize both images as identical.

Thanks everyone for your support.

Martin
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