Image processing - fill in hollow circles

Question

I have a binary black and white images that looks like this

I want to fill in those white circles to be solid white disks. How can I do this in Python

Answer 1

I don't know skimage but if you'd use OpenCv, I would do a Hough transform for circles, and then just draw them over.

Hough Transform is robust, if there are some small holes in the circles that is no problem.

Something like:

circles = cv2.HoughCircles(gray, cv2.cv.CV_HOUGH_GRADIENT, 1.2, 100)

# ensure at least some circles were found
if circles is not None:
    # convert the (x, y) coordinates and radius of the circles to integers
    circles = np.round(circles[0, :]).astype("int")

    # loop over the (x, y) coordinates and radius of the circles
    # you can check size etc here.
    for (x, y, r) in circles:
        # draw the circle in the output image
        # you can fill here.
        cv2.circle(output, (x, y), r, (0, 255, 0), 4)

    # show the output image
    cv2.imshow("output", np.hstack([image, output]))
    cv2.waitKey(0)

See more info here: https://www.pyimagesearch.com/2014/07/21/detecting-circles-images-using-opencv-hough-circles/