opencv 22 histogram

red channel

green channel

blue channel

histogram

#main.py

import numpy as np

import cv2

from matplotlib import pyplot as plt

mountain1 = cv2.imread('assets/mountain2.jpg')

b, g, r = cv2.split(mountain1)

cv2.imshow('img', mountain1)

cv2.imshow('b', b)

cv2.imshow('g', g)

cv2.imshow('r', r)

fig, axs = plt.subplots(1, 3)

axs[0].hist(b.ravel(), 256, [0, 256], color='b')

axs[0].set_title('blue')

axs[1].hist(g.ravel(), 256, [0, 256], color='g')

axs[1].set_title('green')

axs[2].hist(r.ravel(), 256, [0, 256], color='r')

axs[2].set_title('red')

for ax in axs.flat:

    ax.set(xlabel='pixel value', ylabel='count')

# Hide x labels and tick labels for top plots and y ticks for right plots.

for ax in axs.flat:

    ax.label_outer()

#plt.hist(b.ravel(), 256, [0, 256])

#plt.hist(g.ravel(), 256, [0, 256])

#plt.hist(r.ravel(), 256, [0, 256])

fig.suptitle('image histogram')

plt.show()

cv2.waitKey(0)

cv2.destroyAllWindows()

reference:

https://www.youtube.com/watch?v=F9TZb0XBow0&list=PLS1QulWo1RIa7D1O6skqDQ-JZ1GGHKK-K&index=30

matplotlib import ft2font error

pip uninstall matplotlib

pip install -U matplotlib==3.2.0rc1

https://stackoverflow.com/questions/24251102/from-matplotlib-import-ft2font-importerror-dll-load-failed-the-specified-pro

matplotlib multiple plot

https://matplotlib.org/devdocs/gallery/subplots_axes_and_figures/subplots_demo.html