50. 彩色直方图源码

彩色直方图绘制步骤：

• 读取图片信息
• 各通道值计数与归一化
• 设置横纵坐标
• 绘制蓝绿红直方图
• 显示所有直方图

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

# 1 读取图片信息
img = cv2.imread('2.jpg', 1)
imgInfo = img.shape
height = imgInfo[0]
width = imgInfo[1]

# 2 各通道值计数
count_b = np.zeros(256, np.float)
count_g = np.zeros(256, np.float)
count_r = np.zeros(256, np.float)
for i in range(0, height):
    for j in range(0, width):
        (b, g, r) = img[i, j]
        index_b = int(b)
        index_g = int(g)
        index_r = int(r)
        count_b[index_b] =  count_b[index_b] + 1
        count_g[index_g] =  count_g[index_g] + 1
        count_r[index_r] =  count_r[index_r] + 1

# 分别进行归一化处理
for i in range(0, 255):
    count_b[i] = count_b[i] / (height * width)
    count_g[i] = count_g[i] / (height * width)
    count_r[i] = count_r[i] / (height * width)
    
# 3 设置横纵坐标    
x = np.linspace(0, 255, 256)
y1 = count_b
y2 = count_g
y3 = count_r

# 4 绘制蓝绿红直方图
# 绘制蓝色直方图
# 创建画板
plt.figure()
plt.bar(x, y1, 0.9, alpha = 1, color = 'b')

# 绘制绿色直方图
plt.figure()
plt.bar(x, y2, 0.9, alpha = 1, color = 'g')

# 绘制红色直方图
plt.figure()
plt.bar(x, y3, 0.9, alpha = 1, color = 'r')

# 5 显示所有直方图
plt.show()
cv2.waitKey(0)

彩色直方图结果如下：