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How to find the variance of an image?

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sachin
sachin on 12 Sep 2014
Commented: Image Analyst on 25 Mar 2018
i try to find the variance by var function but it shoew the error. I = imread('eight.tif'); var(I)

Accepted Answer

David Young
David Young on 12 Sep 2014
var requires a double or single argument. This will work:
img = double(imread('eight.tif'));
v = var(img);
But note that will give a vector, with one value for the variance of each column of the image. To get the variance of all the pixels in the image, you'll need
v = var(img(:));

More Answers (3)

Dheeraj Kuamr Gupta
Dheeraj Kuamr Gupta on 2 Apr 2017
close all; clear all; clc; I = imread('C:\Users\anubh\Pictures\koala.jpg'); A=rgb2gray(I); [r,c]=size(A) b=r*c; s=0; s=sum(sum(A)); mean=a/b; display(mean); d=(A- mean); display(d);

Morteza Hajitabar Firuzjaei
This code calculates the variance of a RGB image but it's not standard variance, see below:
%------------------------------------------
close all;
clear all;
clc;
I = imread('b.png');
blockSize = [6 6];
varFilterFunction = @(theBlockStructure) var(double(theBlockStructure.data(:)));
blockyImagevar = blockproc(I, blockSize, varFilterFunction);
varianceImage=blockyImagevar(:);
display(varianceImage);
%---------------------------------------
Morteza Hajitabar Firuzjaei

Komal Gaikwad
Komal Gaikwad on 25 Mar 2018
how to display the variance of image in command box
  1 Comment
Image Analyst
Image Analyst on 25 Mar 2018
Leave off the semicolon, or use disp() or fprintf().

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