Get contrast for each channel in an image opencv python

Question

How to calculate each channel contrast in images? Since they are lot of contrast definitions out there

1. Webar Contrast
2. Michelson Contrast
3. RMS contrast

I need to calculate these contrasts.

Answer 1

from PIL import Image
import numpy as np
from numpy import mean, sqrt, square
im = Image.open("leaf.jpg") # Image file name
pixels = list(im.getdata())
width, height = im.size
pixels = np.asarray([pixels[i * width:(i + 1) * width] for i in range(height)], dtype=int)

ch_1 = pixels[:,:,0]
ch_2 = pixels[:,:,1]
ch_3 = pixels[:,:,2]

rms_of_ch1 = sqrt(mean(square(ch_1)))
rms_of_ch2 = sqrt(mean(square(ch_2)))
rms_of_ch3 = sqrt(mean(square(ch_3)))