Would Python 3 and OpenCV allow me to create a motion detection grid?

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Hi sjhalayka, thanks for the response! I'm having trouble finding examples on how to use absdiff for motion detection. All the tutorials and scripts I found for Python motion detection don't seem to work for me. The OpenCV documentation does not provide examples on using absdiff for live video. Can you please help me get started with OpenCV motion detection?

@masterenol: Here is some python code to use the absdifffunction, using an input video. Changing it to use a webcam shouldn't be too hard. A sample test.avi file can be downloaded from https://github.com/sjhalayka/obstacle...

import numpy as np
import cv2

cap = cv2.VideoCapture('test.avi')

ret, last_frame = cap.read()

if last_frame is None:
    exit()

while(cap.isOpened()):
    ret, frame = cap.read()

    if frame is None:
        break

    a = cv2.absdiff(last_frame, frame)

    cv2.imshow('frame', frame)
    cv2.imshow('a', a)

    if cv2.waitKey(33) >= 0:
        break

    last_frame = frame

cap.release()
cv2.destroyAllWindows()

Cool thanks! Using cv2.VideoCapture(0), the code gives me two windows, one very similar to using cv2.createBackgroundSubtractorMOG2() but much cleaner; is this the purpose of using absdiff in the code you provided?

If I understand your question, then yes, this is the purpose of absdiff.

When I use print(a), I get several 3x3 matrices; do I need to understand this in order to code for motion detection? Picture link.

I'm not sure what that's all about, sorry.

Ok, no worries. I'm just trying to figure out how to use absdiff to trigger a response for when motion is detected, for example having the window display the text 'Motion Detected' using cv2.putText().

I think one way would be to do a call to threshold, then see if there are any white pixels in the resulting binarized image (in the regions of interest).

Hi sjhalayka, I'm having trouble with the threshold function. All the tutorials I find online for OpenCV threshold are for single images only, and I don't know how to operate the threshold function when using cv2.VideoCapture(0). Can you please help me again?

Sorry, I don't have a webcam.

a = cv2.absdiff(last_frame, frame)

a = cv2.cvtColor(a, cv2.COLOR_BGR2GRAY)

ret, a = cv2.threshold(a,127,255,cv2.THRESH_BINARY)