Walking circle_perimeter

Hi Guys, I'm trying to subsample the points returned by circle_perimeter and I'm having trouble. Since the points are calculated in octants (and reflected?) it makes walking it somewhat confusing (see below) Does anyone know off hand how I could walk this thing clockwise for example (or produce a sensible subsample of e.g., every other point or every 4th point, etc). To be a little more concrete: from skimage.draw import circle_perimeter rr, cc = circle_perimeter(12, 12, 10) im = zeros((40,40)) im[rr[::4],cc[::4]] = 1 imshow(im, cmap=cm.gray) # returns one quadrant of the circle Still Googling, but I'd appreciate any help =) Thanks, Dan