How to calculate the color pixel value in each row and column

Question

I am working with an example of how to calculate the value of each pixel in each row and column using the following formula using Python.

Formula is

where M represents image matrix dimension N represents total number of pixels and P(i, j) is the color pixel value at ith row and jth column

yes You are right I need to compute mean of pixel value and the Shape of the image is : (204, 220, 3) — KABIL, Jan 11 '20 at 11:56
Do you want to compute the mean value for every channel(red_mean, green_mean, blue_mean) or the overall mean? — cristian hantig, Jan 11 '20 at 13:41

cristian hantig · Answer 1 · 2020-01-12T10:42:40.477

1

You can use numpy if you re using python

import numpy as np
import cv2 

img = cv2.imread('img.png')
# in case of overall mean
np.mean(img)

#in case of channel wise mean
np.mean(img, axis=(0, 1))

This can be applied if your matrix has rectangular shape

edited Jan 12 '20 at 10:42

answered Jan 11 '20 at 11:42

cristian hantig

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thanks for your comment can u please explain me with an example so that i can clearly understand. – KABIL Jan 11 '20 at 11:46

score 1 · Answer 2 · answered Jan 12 '20 at 01:40

The average of the pixel channels is fairly trivial to calculate, but not necessarily very meaningful - depending on the use case it is more illustrative to find the dominant colors. This answer demonstrates an approach to finding the dominant colors.

Here is a toy example for finding the channel-wise means of the image pixels using the image

import cv2
import numpy as np

im = cv2.imread('opencvtest.png')

# Find the average of each channel across the image
mean = [np.mean(im[:,:,i]) for i in range(im.shape[2])]

print(mean)

[132.6709785196566, 92.74899063496903, 81.57176387455432]

So the average color the code found is

which is consistent with what I would expect from looking at the test image.

Thank you this is the one which I need. – KABIL Jan 12 '20 at 13:30 — KABIL, Jan 12 '20 at 13:30

How to calculate the color pixel value in each row and column

2 Answers2