How to compare 2 images from command line
andrewlylegould at gmail.com
Tue Sep 2 16:02:31 UTC 2008
On Tue, Sep 2, 2008 at 10:31 AM, FreeBSD <freebsd at optiksecurite.com> wrote:
> Andrew Gould a écrit :
>> On Tue, Sep 2, 2008 at 10:23 AM, FreeBSD <freebsd at optiksecurite.com<mailto:
>> freebsd at optiksecurite.com>> wrote:
>> Tom Marchand a écrit :
>> Hash the images and compare the hashes.
>> -------------- Original message ----------------------
>> From: FreeBSD <freebsd at optiksecurite.com
>> <mailto:freebsd at optiksecurite.com>>
>> 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,
>> 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
>> 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."?
> 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.
> Thank you for your interest
Are you simply trying to determine whether the mplayer has finished playing
a movie (that you're not watching)? It seems to me that the fact that the
image changes is not a good indication that mplayer is "working correctly",
only that the movie isn't running.
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