[FIXED] How to get statistics from a histogram?

Issue

I'm trying to get the four first order histogram statistics (mean, variance, skewness and kurtosis) from a histogram.

I have this code that calculates the histogram:

import cv2
from matplotlib import pyplot as plt

img1 = 'img.jpg'
gray_img = cv2.imread(img1, cv2.IMREAD_GRAYSCALE)
plt.hist(gray_img.ravel(),256,[0,256])
plt.title('Histogram for gray scale picture')
plt.show()

How can I get that statistics?

Solution

Based on my answer here

def mean_h(val, freq):
    return np.average(val, weights = freq)

def var_h(val, freq):
    dev = freq * (val - mean_h(val, freq)) ** 2
    return dev.sum() / freq.sum()

def moment_h(val, freq, n):
    n = (freq * (val - mean_h(val, freq)) ** n).sum() / freq.sum()
    d = var_h(val, freq) ** (n / 2)
    return n / d

skewness and kurtosis are just the 3rd and 4th moments

Answered By - Daniel F