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