opencv+python学习记录（七）灰度直方图

灰度直方图是图像灰度级的函数，用来描述每个灰度级在图像矩阵中的像素个数或者占有率。对于8位图来说， 图像的灰度级范围是0-255之间的整数，通过定义函数calcGrayHist来计算灰度直方图。

#-*-coding:utf-8-*-

import cv2 as cv

import numpy as np

import matplotlib.pyplot as plt

def calcGrayHist(image):

gray= cv.cvtColor(image, cv.COLOR_BGR2GRAY)

rows, cols= gray.shape

#存储灰度直方图

grayHist= np.zeros([256], np.uint64)

for r in range(rows):

      for c in range(cols):

          grayHist[gray[r][c]]+= 1

  return grayHist

if __name__== "__main__":

    print("---------------Hello python ------------")

    filename= ("basketball.jpg")

    src= cv.imread(filename)

    cv.namedWindow("input image", cv.WINDOW_AUTOSIZE)

    grayHist= calcGrayHist(src)

    x_range= range(256)

    plt.plot(x_range, grayHist,'r',linewidth=2,c='black')

    y_maxvalue= np.max(grayHist)

    plt.axis([0,255,0, y_maxvalue])

    plt.xlabel('gray Level')

    plt.ylabel('number of pixels')

    plt.show()