OpenCV 'BackgroundSubtractorMOG2' for two images

Question

I am trying to highlight differences between two almost similar image masks using OpenCV's BackgroundSubtractorMOG2 method.

My Code:

def Approach_2():
    img = [0, 0]
    img[0] = cv2.imread('images/4-left.PNG', cv2.IMREAD_GRAYSCALE)
    img[1] = cv2.imread('images/4-right.PNG', cv2.IMREAD_GRAYSCALE)

    img[0], img[1] = make_similar(img[0], img[1]) # make two images similar (equal width and height) by applying scaling, translation and performs Canny edge detection on two images

    fps = 5

    fgbg = cv2.createBackgroundSubtractorMOG2(detectShadows=True)

    cv2.imshow("A", img[0])
    cv2.imshow("B", img[1])

    i = 1
    while(True):

        frame = img[i]
        i = 1-i
        fgmask = fgbg.apply(frame)        

        cv2.imshow('original', frame)
        cv2.imshow('fg', fgmask)
        # cv2.imshow('fg', cv2.bitwise_and(frame, frame, mask=fgmask))

        time.sleep(1 / fps)

        if(cv2.waitKey(1) & 0xFF == ord('q')) : break

    cv2.destroyAllWindows()

if __name__ == '__main__':
    Approach_2()

But i am getting only blank 'fgmask'.

Any suggestions. ?

Answer 1

As stated in the comments, you should bitwise operations. It is easier and far more efficient. You can read about it here

To add some extra information: a backgroundsubtractor can (with some trickery) be used on still images, but it is intended for video. You can find sample code here

As to your code, it does not establish a solid background, because it alternates the two source images on every frame. Therefor the result is a blank mask.