how can i calculate variance of the intensity in an gray scale image

in order to find the sigmoid function value of the image , i need the value of *mean and variance of the intensity of the image *

Answer 1

[chitresh]

a = imread('input.tif'); % convet uint8 to double a_double = double(a); % get number of rows and columns value [r,c] = size(a); % mean of gray scale image total_mean = sum(a_double(:))/(r*c); % variance of gray scale image total_difference = (a_double - total_mean).^2; total_sum = sum(total_difference(:)); limit = (r*c)-1; total_variance = total_sum/limit;

please accept answer if its ok with you

Answer 2

[Image Analyst]

meanGrayLevel = mean2(grayImage); % or mean(grayImage(:));
variance = var(grayImage(:));

[chitresh]

if you trying above code then try this else u find some error

grayimage_double = double(grayimage);

variance = var(grayimage_double);