Python-OpenCVで図形の縁を検出するルーチンを考える

#!/usr/bin/env python3
# coding: utf8

import cv2
import numpy as np

def createBaseImage():
    # 黒色のキャンバス(512x512)作成
    img = np.full((512, 512), 0, dtype=np.uint8)
    # 円を描画
    color = 255 # 白
    radius = 128 # 半径
    center = (256, 256) # 中心
    cv2.circle(img, center, radius, color, thickness=16, lineType=cv2.LINE_8, shift=0)
    return img
def getFutidoriImage(gray):
    h, w = gray.shape[:2]
    # 黒色のキャンバスを作成
    img = np.full((h,w), 0, dtype=np.uint8)
    # ループ
    for y in range(1, h-1):
        for x in range(1, w-1):
            if (gray[y][x] > 0):
                continue
            # 左を検査
            if (gray[y][x-1] > 0):
                img[y][x] = 255
                continue
            # 上を検査
            if (gray[y-1][x] > 0):
                img[y][x] = 255
                continue
            # 右を検査
            if (gray[y][x+1] > 0):
                img[y][x] = 255
                continue
            # 下を検査
            if (gray[y+1][x] > 0):
                img[y][x] = 255
                continue
    return img

img = createBaseImage()
cv2.imwrite("./BaseImage.png", img)
result = getFutidoriImage(img)
cv2.imwrite("./FutidoriImage.png", result)