[Python] Copy a part of an image in opencv and python

I'm trying to split an image into several sub-images with opencv by identifying templates of the original image and then copy the regions where I matched those templates. I'm a TOTAL newbie to opencv! I've identified the sub-images using:

result = cv2.matchTemplate(img, template, cv2.TM_CCORR_NORMED)


After some cleanup I get a list of tuples called points in which I iterate to show the rectangles. tw and th is the template width and height respectively.

for pt in points:
re = cv2.rectangle(img, pt, (pt[0] + tw, pt[1] + th), 0, 2)
print('%s, %s' % (str(pt[0]), str(pt[1])))
count+=1


What I would like to accomplish is to save the octagons (https://dl.dropbox.com/u/239592/region01.png) into separated files.

How can I do this? I've read something about contours but I'm not sure how to use it. Ideally I would like to contour the octagon.

Thanks a lot for your help!

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