# Construct the substrate instance first.
#
ref_img = cv2.imread(get_sample_path("ref.png"), cv2.IMREAD_GRAYSCALE)
ref = Reference(
    cv2.threshold(ref_img, 0, 255, cv2.THRESH_BINARY | cv2.THRESH_OTSU)[1],
    (10, 10, 1250, 200),
    (100, 100, 1200, 500),
)
subst = RectSubstrate(ref, 3.0, 1.0, 0.01)
#
# Construct the coating layer instance.
#
target_img = cv2.imread(get_sample_path("coat.png"), cv2.IMREAD_GRAYSCALE)
coat = RectIfdRoughness(
    cv2.threshold(target_img, 0, 255, cv2.THRESH_BINARY | cv2.THRESH_OTSU)[1],
    subst,
    "arithmetic",
    5.0,
    (1, 1),
    50,
)
#
# Visualize the coating layer.
#
import matplotlib.pyplot as plt #doctest: +SKIP
plt.imshow(coat.draw()) #doctest: +SKIP