Esperimenti con filtri Canny ed Hough Lines con OpenCV

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import cv2

import numpy as np

from matplotlib import pyplot as plt

img = cv2.imread('casa.jpg')

gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# parametri automatici Canny

#ret,th = cv2.threshold(gray,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)

#edges = cv2.Canny(img,ret,ret*0.5)

v = np.median(gray)

sigma = 0.3

lower = int(max(0,(1.0-sigma)*v))

upper = int(max(0,(1.0+sigma)*v))

print lower

print upper

edges = cv2.Canny(img,lower,upper)

cv2.imwrite('canny_casa.jpg',edges)

lines = cv2.HoughLines(edges,1.5,np.pi/180,370)

for rho,theta in lines[0]:

    a = np.cos(theta)

    b = np.sin(theta)

    x0 = a*rho

    y0 = b*rho

    x1 = int(x0 + 1000*(-b))

    y1 = int(y0 + 1000*(a))

    x2 = int(x0 - 1000*(-b))

    y2 = int(y0 - 1000*(a))

    cv2.line(img,(x1,y1),(x2,y2),(0,0,255),2)

cv2.imwrite('risultato_casa.jpg',img)