실습 4 — 닫기로 끊긴 글자와 구멍 메우기

import cv2
import numpy as np

clean = cv2.imread("ch09_letters_clean.png", cv2.IMREAD_GRAYSCALE)
broken = cv2.imread("ch09_letters_broken.png", cv2.IMREAD_GRAYSCALE)

def blobs(binary):
    return cv2.connectedComponents(binary)[0] - 1

def diff(out):
    """본래 글자와 값이 다른 칸의 수"""
    return int((out != clean).sum())

print("본래 글자: 흰 칸", int((clean == 255).sum()), "/ 흰 덩어리", blobs(clean))
print("끊긴 글자: 흰 칸", int((broken == 255).sum()), "/ 흰 덩어리", blobs(broken))
print("다른 칸:", diff(broken))

closed = {}
for k in [3, 5, 7, 9, 11]:
    se = cv2.getStructuringElement(cv2.MORPH_RECT, (k, k))
    # MORPH_CLOSE: 팽창한 뒤 같은 도장으로 침식
    closed[k] = cv2.morphologyEx(broken, cv2.MORPH_CLOSE, se)
    print(f"닫기 {k:2}×{k:<2}: 흰 덩어리 {blobs(closed[k])}, 다른 칸 {diff(closed[k])}")

kinds = {"RECT": cv2.MORPH_RECT, "CROSS": cv2.MORPH_CROSS, "ELLIPSE": cv2.MORPH_ELLIPSE}
by_shape = {}
for name, shape in kinds.items():
    se = cv2.getStructuringElement(shape, (5, 5))
    by_shape[name] = cv2.morphologyEx(broken, cv2.MORPH_CLOSE, se)
    print(f"닫기 5×5 {name:8}: 흰 덩어리 {blobs(by_shape[name])}, 다른 칸 {diff(by_shape[name])}")

# 다른 칸이 가장 적은 모양을 골라 저장한다
best = min(by_shape, key=lambda name: diff(by_shape[name]))
cv2.imwrite("out_ch09_closed.png", by_shape[best])
print("가장 좋은 모양:", best)
print("저장: out_ch09_closed.png")

import matplotlib.pyplot as plt

plt.rcParams["font.family"] = "Malgun Gothic"
plt.rcParams["axes.unicode_minus"] = False

panels = [("끊긴 글자", broken)] + [(f"닫기 {k}×{k}", closed[k]) for k in [3, 5, 7, 9]]
panels.append(("본래 글자", clean))
fig, axes = plt.subplots(2, 3, figsize=(12, 4.2))
for ax, (title, im) in zip(axes.flat, panels):
    ax.imshow(im, cmap="gray", vmin=0, vmax=255)
    ax.set_title(f"{title} (덩어리 {blobs(im)}, 다른 칸 {diff(im)})")
    ax.axis("off")
plt.tight_layout()
plt.show()