Comparing images

nanneman

Background:

I have a webcam that takes a new pic every minute. This picture is archived at my webserver and the latest is shown on my website.

Problem:

Then everybody is out of office I dont want to show that. I also want it to delete pictures that are simular to save diskspace.

I also figured out that I could make it to be a security cam. At night the camera doesnt show a black image on the website. Just the last image then it was light. If somebody breakes in, the camera will detect that the images are diffrent and saves them in a special dir.

My boss said something about the pmn programs in linux but I doesnt understand much... :/

Well... well... hope that you can help me with this cool feature.

[deleted]

Indeed, there are programs that can do exactly this with your webcam, they record images only when there is significant motion in the scene.

Otherwise you'd have to convert the images to BMP format (Bitmaps) and compare regions of the image with the same regions in other images.
That is a pretty hefty thing to do, lots of number-juggling. (in bw it's 300x200 = 60k pixels, that means 60k comparisons between the two pictures...and if you use color images, it's 3 times that amount (red green blue))

I'd leave that to a programming language like C or C++.
PHP is not designed to do this.

Anon

Ack 🙁

I need to look for a program that does it and can return the result to php then.

Do you have any suggestions where I can look?
I use linux as OS

andreas

You can write a application in c that you call from PHP and get the result back.. But I'd do as little as posible in PHP... cuz you need a much faster language, like C...

When you have written the app in C just exec(); it from php and everything should work..

Andreas

nanneman

My C programing skills is very low. I hoped that someone here knew where I could find that software. I´m pretty sure that someone has come up with this idea before me.

Anon

I have recently setup a similar setup to what you have done - did you manage to get anything to help this problem?

Thanks

Tom

Anon

The software that does it is called: WebCam32 and it was created by Surveyor.com.

It is designed to FTP images from a web cam to a server, and, once there, you do with them what you want. You can instruct WebCam32 to compare the images, and set a percentage threshold for whether or not to move the image.

At the same time (this is the cool part) it can save those same images in an AVI file so that, at the end of the day, you can review all the images in a couple of minutes by playing the movie. I do this, taking a picture every second using a 10% change threshold, and the resulting AVI is less than 2MB over 12 hours.