Question

I have a working connected components analysis code working in C. It’s actually a copy from the book “Learning Opencv”.

Now I am rewriting all that code to Python and I cannot find some of that function in the Python API, like cvStartFindContours.

I am wondering is somebody has a basic connected components analysis function implemented in Python. I know there are some libraries, but I am searching for something simpler, just a function or a piece of code.

I don’t need anything “big” because I have a plain black image with 2 or 3 white circles, and I want to find the number of circles and its center.

I know I can probably code on myself but I prefer to use somebody’s function or simple library.

EDIT: I solved it the following way.

def find_connected_components(img):
    """Find the connected components in img being a binary image.
    it approximates by rectangles and returns its centers
    """

    storage = cv.CreateMemStorage(0)
    contour = cv.FindContours(img, storage, cv.CV_RETR_CCOMP, cv.CV_CHAIN_APPROX_SIMPLE)
    centers = []

    while contour:
        # Approximates rectangles
        bound_rect = cv.BoundingRect(list(contour))

        centers.append(bound_rect[0] + bound_rect[2] / 2, bound_rect[1] + bound_rect[3] / 2)

        contour = contour.h_next()

Answer 1

You should take a look at the documentation. As of OpenCV 2.2 there is a complete new interface for Python which covers all C/C++ functions 🙂

cv.FindContours should work for you 🙂