Capture an image after some requeriments

Programming Questions

ver4891

Capture an image after some requeriments

in Programming Questions • 3 years ago

Hi!
I'm new at the forum but I've been using it for a while.
I'm working on a project that uses a camera, and where I must track if there is any change in the background. For that I'm using Background Difference. If there is any change or movement, I must get ready to take an snapshot, but when do I have to do this? when there is no movements or changes. The problem I have is that this new background without changes is different as the one in the beginning.

I'll try to explain better: I want to have a scenario where are people writing. The camera needs to know when someone approach and then goes away. At the moment when the person goes away I need the camera to capture the image, that will have the word that the person wrote. For the second part I'm using the Thresholding background (example in the core library), but I'm not sure it will work always as I want. I would like to know if there is any other option, easier and probably much better than what I'm doing.

I appreciate any help in advance.

Replies(2)

heedless

Re: Capture an image after some requeriments

3 years ago

I think there are two things you can do:

Place the camera in such a way that it shows a bit of the user, like his/her upper body. Then just check that area of the screen against the background image (not the paper area). If you detect movement, someone has entered the screen. When the person leaves, the original background will be shown again so the background difference will be none/small.

Or you could do something like this:

Use the background difference like you are doing now (lets call this image bg1). When you have noticed a difference, save the current frame as a second image (this would be bg2).

Then, compare bg2 to the current videoframe every 3 seconds or so (to minimize the chance of thinking the user left when he is just holding still his hand). For example, at 30 fps this will trigger your action every 3 seconds (the timing won't always be precise, but that doesn't matter)

if(frameCount==0){
//do stuff
}

If there is a difference between bg2 and the current image, someone is still moving. When bg2 and the current image are the same for period of time (like those 3 seconds) it means the person has stopped moving / went away. Save the image and use it as your new bg1.

(You can probably do this with just one image instead of using bg1 and bg2 but it's easier to explain using 2 images).

ver4891

Re: Re: Capture an image after some requeriments

3 years ago

Thanks for your reply!...

I'll try the code you say and will tell you how it goes...

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