06: 阈值分割

import cv2

# 灰度图读入
img = cv2.imread('gradient.jpg', 0)

# 阈值分割
ret, th = cv2.threshold(img, 127, 255, cv2.THRESH_BINARY)
cv2.imshow('thresh', th)
cv2.waitKey(0)Copy to clipboardErrorCopied

import matplotlib.pyplot as plt

# 应用5种不同的阈值方法
ret, th1 = cv2.threshold(img, 127, 255, cv2.THRESH_BINARY)
ret, th2 = cv2.threshold(img, 127, 255, cv2.THRESH_BINARY_INV)
ret, th3 = cv2.threshold(img, 127, 255, cv2.THRESH_TRUNC)
ret, th4 = cv2.threshold(img, 127, 255, cv2.THRESH_TOZERO)
ret, th5 = cv2.threshold(img, 127, 255, cv2.THRESH_TOZERO_INV)

titles = ['Original', 'BINARY', 'BINARY_INV', 'TRUNC', 'TOZERO', 'TOZERO_INV']
images = [img, th1, th2, th3, th4, th5]

# 使用Matplotlib显示
for i in range(6):
    plt.subplot(2, 3, i + 1)
    plt.imshow(images[i], 'gray')
    plt.title(titles[i], fontsize=8)
    plt.xticks([]), plt.yticks([])  # 隐藏坐标轴

plt.show()Copy to clipboardErrorCopied

# 自适应阈值对比固定阈值
img = cv2.imread('sudoku.jpg', 0)

# 固定阈值
ret, th1 = cv2.threshold(img, 127, 255, cv2.THRESH_BINARY)
# 自适应阈值
th2 = cv2.adaptiveThreshold(
    img, 255, cv2.ADAPTIVE_THRESH_MEAN_C, cv2.THRESH_BINARY, 11, 4)
th3 = cv2.adaptiveThreshold(
    img, 255, cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY, 17, 6)

titles = ['Original', 'Global(v = 127)', 'Adaptive Mean', 'Adaptive Gaussian']
images = [img, th1, th2, th3]

for i in range(4):
    plt.subplot(2, 2, i + 1), plt.imshow(images[i], 'gray')
    plt.title(titles[i], fontsize=8)
    plt.xticks([]), plt.yticks([])
plt.show()Copy to clipboardErrorCopied