How to circle moving objects using opencv?

Question

I have a video file and I need to circle all moving objects in a certain frame I select. My idea of a solution to this problem is: Circle all moving objects (white areas) on a video on which was applied motion detector and circle the same areas on the original frame.

I am using BackgroundSubtractorGMG() from cv2 to detect movement

Below I show the way I expect this program to work(I used to paint, so I am now sure this is correct, but I hope it is good enough to demonstrate the concept)

You can use this approach: take the binary result from the BackgroundSubtractorGMG, apply [Morphological Transformations](https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_imgproc/py_morphological_ops/py_morphological_ops.html#morphological-transformations) to remove noise, detect white shapes using [findContours](https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_imgproc/py_contours/py_contours_begin/py_contours_begin.html#contours-getting-started), — J.D., Aug 15 '19 at 19:30
then draw the [boundingrect](https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_imgproc/py_contours/py_contour_features/py_contour_features.html#bounding-rectangle) for each contour. — J.D., Aug 15 '19 at 19:30

score 1 · Answer 1 · answered Aug 27 '19 at 09:52

As others have said in comments:

Get the mask from you background subtraction algorithm
use cv.findContours(mask, ...) to find contours
(optional) select which contours you want to keep (something like ((x, y), radius) = cv.minEnclosingCircle(contour) or a, b, w, h = cv.boundingRect(c) and if radius > 5
use drawing functions like cv.rectangle or similar to draw the shape around the contour (like so: cv.rectangle(img, (a, b), (a + w, b + h), (0, 255, 0), 2))

How to circle moving objects using opencv?

1 Answers1