Date: Wed, 03 Sep 2008 10:34:34 +0200 From: "DA Forsyth" <iwrtech@iwr.ru.ac.za> To: freebsd-questions@freebsd.org Cc: freebsd@optiksecurite.com Subject: Re: How to compare 2 images from command line Message-ID: <48BE683A.13293.2D4930EF@iwrtech.iwr.ru.ac.za> In-Reply-To: <20080902173329.867AC106571B@hub.freebsd.org> References: <20080902173329.867AC106571B@hub.freebsd.org>
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On 2 Sep 2008 , freebsd-questions-request@freebsd.org entreated about
"freebsd-questions Digest, Vol 231, Issue 5":
> > 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.
JPG format will always be different because of the
encoding/compression. I think you need to save to an uncompressed
format like BMP. Maybe PNG has a mode that will work too. BMP has
no info headers, just the raw data, so that won't be affected by the
time of the save (at the least).
--
DA Fo rsyth Network Supervisor
Principal Technical Officer -- Institute for Water Research
http://www.ru.ac.za/institutes/iwr/
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