ハフ変換

hough.py

import math
import matplotlib.pyplot as plt
import numpy as np
import cv2
import math

img = cv2.imread("test.bmp", 0)

rhoMax = int(math.hypot(img.shape[0], img.shape[1]))

hough = np.zeros((90, rhoMax), np.uint8)

poss = np.where(img == 0)
for i in range(len(poss[0])):
    y = poss[0][i]
    x = poss[1][i]
    for degree in range(90):
        theta = math.radians(degree)
        rho = int(x * math.cos(theta) + y * math.sin(theta))
        hough[degree][rho] += 1

argmax = hough.argmax()
degree = int(argmax / rhoMax)
radian = math.radians(degree)
rho = argmax % rhoMax

out = cv2.imread("test.bmp")
x1 = 0
y1 = (rho - x1 * math.cos(radian)) / math.sin(radian)
x2 = out.shape[1]
y2 = (rho - x2 * math.cos(radian)) / math.sin(radian)
cv2.line(out, (int(x1), int(y1)), (int(x2), int(y2)), (0,255,0), 2)
cv2.imwrite("out.png", out)