Python OpenCV实例：直方图计算（数学公式简单实现）

#coding:utf-8
'''
直方图
'''

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

'''
计算RGB图像每个通道的直方图
'''
def cal_histgram_rgb(image):
    image_rgb = cv2.cvtColor(image,cv2.COLOR_BGR2RGB)
    channel_r,channel_g,channel_b = cv2.split(image_rgb)

    r_hist = np.zeros((256,),np.int32).tolist()
    g_hist = np.zeros((256,),np.int32).tolist()
    b_hist = np.zeros((256,),np.int32).tolist()

    rows,cols,_ = image.shape

    for y in range(rows):
        for x in range(cols):
            r_hist[channel_r[y,x]] += 1
            g_hist[channel_g[y,x]] += 1
            b_hist[channel_b[y,x]] += 1

    return r_hist,g_hist,b_hist

def cal_hist_gray(image):
    gray = cv2.cvtColor(image,cv2.COLOR_RGB2GRAY)
    rows,cols = gray.shape
    hist_data = np.zeros((256,),np.int32).tolist()
    for y in range(rows):
        for x in range(cols):
            hist_data[gray[y,x]] += 1

    return hist_data

image = cv2.imread('datas/l1.jpg')

hist_r,hist_g,hist_b = cal_histgram_rgb(image)
hist_data = cal_hist_gray(image)

# 坐标
x = np.arange(0,256)

_, axarr = plt.subplots(2,2)
plt.xlim(0,255)
axarr[0,0].bar(x,hist_data)
axarr[0,1].bar(x,hist_r,color='r')
axarr[1,0].bar(x,hist_g,color='g')
axarr[1,1].bar(x,hist_b,color='b')

plt.show()