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#!/usr/bin/env python
'''
This program illustrates the use of findContours and drawContours.
The original image is put up along with the image of drawn contours.
Usage:
contours.py
A trackbar is put up which controls the contour level from -3 to 3
'''
import numpy as np
import cv2
def make_image():
img = np.zeros((500, 500), np.uint8)
black, white = 0, 255
for i in xrange(6):
dx = (i%2)*250 - 30
dy = (i/2)*150
if i == 0:
for j in xrange(11):
angle = (j+5)*np.pi/21
c, s = np.cos(angle), np.sin(angle)
x1, y1 = np.int32([dx+100+j*10-80*c, dy+100-90*s])
x2, y2 = np.int32([dx+100+j*10-30*c, dy+100-30*s])
cv2.line(img, (x1, y1), (x2, y2), white)
cv2.ellipse( img, (dx+150, dy+100), (100,70), 0, 0, 360, white, -1 )
cv2.ellipse( img, (dx+115, dy+70), (30,20), 0, 0, 360, black, -1 )
cv2.ellipse( img, (dx+185, dy+70), (30,20), 0, 0, 360, black, -1 )
cv2.ellipse( img, (dx+115, dy+70), (15,15), 0, 0, 360, white, -1 )
cv2.ellipse( img, (dx+185, dy+70), (15,15), 0, 0, 360, white, -1 )
cv2.ellipse( img, (dx+115, dy+70), (5,5), 0, 0, 360, black, -1 )
cv2.ellipse( img, (dx+185, dy+70), (5,5), 0, 0, 360, black, -1 )
cv2.ellipse( img, (dx+150, dy+100), (10,5), 0, 0, 360, black, -1 )
cv2.ellipse( img, (dx+150, dy+150), (40,10), 0, 0, 360, black, -1 )
cv2.ellipse( img, (dx+27, dy+100), (20,35), 0, 0, 360, white, -1 )
cv2.ellipse( img, (dx+273, dy+100), (20,35), 0, 0, 360, white, -1 )
return img
if __name__ == '__main__':
print __doc__
img = make_image()
h, w = img.shape[:2]
_, contours0, hierarchy = cv2.findContours( img.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
contours = [cv2.approxPolyDP(cnt, 3, True) for cnt in contours0]
def update(levels):
vis = np.zeros((h, w, 3), np.uint8)
levels = levels - 3
cv2.drawContours( vis, contours, (-1, 3)[levels <= 0], (128,255,255),
3, cv2.CV_AA, hierarchy, abs(levels) )
cv2.imshow('contours', vis)
update(3)
cv2.createTrackbar( "levels+3", "contours", 3, 7, update )
cv2.imshow('image', img)
0xFF & cv2.waitKey()
cv2.destroyAllWindows()