線画を抽出するプログラム

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import cv2
import numpy as np

def make_contour_image(path):
    neiborhood24 = np.array([[1, 1, 1, 1, 1],
                             [1, 1, 1, 1, 1],
                             [1, 1, 1, 1, 1],
                             [1, 1, 1, 1, 1],
                             [1, 1, 1, 1, 1]],
                             np.uint8)
    # グレースケールで画像を読み込む.
    gray = cv2.imread(path, cv2.IMREAD_GRAYSCALE)
    cv2.imwrite("gray.jpg", gray)

    # 白い部分を膨張させる.
    dilated = cv2.dilate(gray, neiborhood24, iterations=1)
    cv2.imwrite("dilated.png", dilated)

    # 差をとる.
    diff = cv2.absdiff(dilated, gray)
    cv2.imwrite("diff.png", diff)

    # 白黒反転
    contour = 255 - diff
    cv2.imwrite("./output.png", contour)
    return contour

if __name__ == '__main__':
    make_contour_image("a.png")