OpenCV图像处理---绘制灰度直方图

import cv2
import numpy as np
import matplotlib.pyplot as plt
import time


def calcGrayHist(I):
    # 计算灰度直方图
    h, w = I.shape[:2]
    grayHist = np.zeros([256], np.uint64)
    for i in range(h):
        for j in range(w):
            grayHist[I[i][j]] += 1
    return grayHist



if __name__ == "__main__":
    img_path = "./0.jpg"
    frame = cv2.imread(img_path)
    cv2.imshow("img",frame)

    frame_gray = cv2.cvtColor(frame, cv2.COLOR_RGB2GRAY)
    cv2.imshow("img_gray",frame_gray)
    cv2.waitKey(0)


    grayHist = calcGrayHist(frame_gray)

    x = np.arange(256)
    # 绘制灰度直方图
    plt.plot(x, grayHist, 'r', linewidth=2, c='black')
    plt.xlabel("gray Label")
    plt.ylabel("number of pixels")
    plt.show()