Images not updated

I am working on 3D reconstruction exercise. I am trying to show up in the 2d images the matching points I find with my algorithm. I am using a loop like:

while True:
    if generating:
        i += 1
        left_point, right_point = next(gen, (None, None))

        if left_point is not None:
            color = [np.random.randint(256), np.random.randint(256), np.random.randint(256)]
            p1 = np.flip(left_point)
            p2 = np.flip(right_point)

            left_image = cv2.circle(left_image, center=p1, radius=5, color=color, thickness=2)
            right_image = cv2.circle(right_image, center=p2, radius=5, color=color, thickness=2)

            print(f"Generated {i} points ({i / (time.time() - start):.4f} points/second)", end='\r')
            GUI.showImages(left_image, right_image, True)
        else:
            print("")
            print("Finished generating points")
            cv2.imwrite("/root/left_image_points2.png", left_image)
            cv2.imwrite("/root/right_image_points2.png", right_image)
            GUI.showImages(left_image, right_image, True)
            generating = False

None of the showImages call in the loop updates the images. I have tried saving them to disk to check out that points are really there, and they are, as can be seen in attached image.

left_image_points2

Am I doing something wrong?

Thanks and kind regards