How to find energy of an image

I want to find the energy of an image using the formula given in the attached image. Please help.

[anushka huilgol]

i have a doubt not related to this question

i have to find the energy of an image and i have code ready with me but i just quite cant understand the error shown by it in matlab could someone please help me??

code:

clc;
clear all;
close all;
 A=imread('peppers.png');
 g=rgb2gray(A);

   figure, imshow(g);
  x=xpy(g);
   [p q]=size(g);

   for i=1:m
   for    j=1:n

       sen(i)=(p(i)*log(p(i)));
   end
   sen=sum(sen);
   end

[anushka huilgol]

sorry its entropy not energy

[Walter Roberson]

You do not show the error message.

What is xpy?

size() is going to return p and q as scalars, but in your for loop you are using p as a vector. Your "for j" loop also does not refer to j at all, so there is no point in using a loop there if the code is correct.

[Image Analyst]

If "i have a doubt not related to this question" then you should start your own question so we don't bug Dhrubajyoti Das with emails about updates to his question. In that question, I will answer with how you used the size function incorrectly.

Answer 1

[Image Analyst]

Assuming F is the Fourier Transform, try fft2().

[Dhrubajyoti Das]

but sir, how to find the value of 't' as shown in the attached image.

[Image Analyst]

F = fft2(grayImage) -- did you try it? Did you try anything like the code below:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures if you have the Image Processing Toolbox.
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 24;

%===============================================================================
% Read in a standard MATLAB gray scale demo image.
folder = fileparts(which('cameraman.tif')); % Determine where demo folder is (works with all versions).
baseFileName = 'cameraman.tif';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
if numberOfColorBands > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 

% Take the Fourier Transform.
F = fft2(grayImage);

realF = log(real(F));
% Display the original gray scale image.
subplot(2, 2, 2);
imshow(realF, []);
title('Original Grayscale Image', 'FontSize', fontSize);

% Sum up the values.
magImage = abs(F).^2;
energy = sum(magImage(:))