what is meant by GLCM MEAN (average) ?

i want to know the meaning of GLCM MEAN..

how can i calculate it in matlab?

what is the syntax?

reply soon

Answer 1

[Youssef Khmou]

GLCM stand for : Grey-Level Co-occurrence Matrix ,

More info/examples can be found in the following URL :

http://www.fp.ucalgary.ca/mhallbey/tutorial.htm

[REHAN AHMAD]

how to calculate GLCM feature correlationmatlab

Answer 2

[Image Analyst]

It's the Gray Level Co-occurrence Matrix. It basically is kind of like a histogram of how many times a certain gray level occurs next to other gray levels in an image. Sometimes used in texture analysis. It is performed by the function graycomatrix() in the Image Processing Toolbox.

[Youssef Khmou]

thanks for sharing, so an example :

 G=graycomatrix(imread('liftingbody.png'));

it gives 8x8 matrix , so why exactly 8x8?

[angel]

ok sir... i know glcm is caculated as

glcm=graycomatrix(image);

i've divided the image into non overlapping blocks...the code is like this...

blockSizeR = 32;% Rows in block.
blockSizeC = 32; % Columns in block.

% Figure out the size of each block.

 wholeBlockRows = floor(rows / blockSizeR);
 wholeBlockCols = floor(columns / blockSizeC);
 fprintf('\nSize of whole block is %d x   %d\n\n',wholeBlockRows,wholeBlockCols); 

 % Now scan though, getting each block and putting it as a slice of a 3D array.
   blockNumber = 1;

 for row = 1 : blockSizeR : rows
  for col = 1 : blockSizeC : columns
    row1 = row;
    row2 = row1 + blockSizeR - 1;
    row2 = min(rows, row2);

% Determine starting and ending columns.

                col1 = col;
    col2 = col1 + blockSizeC - 1;
    col2 = min(columns, col2); % Don't let it go outside the image.
    % Extract out the block into a single subimage.
    oneBlock = grayImage(row1:row2, col1:col2);

               subplot(8,8,blockNumber);
               imshow(oneBlock);
               caption = sprintf('Block #%d\n of 64', blockNumber);
    title(caption, 'FontSize', fontSize);
    
               blockNumber = blockNumber + 1;

       end

   end

 figure,imshow(grayImage, []);

 title('original image');

sir plz can u tell me by writing a piece of code to calculate the GLCM MEAN..

[Raman]

@Youssef KHMOU sir as i m working on my project...m not decided yet exactly what should it be(block size)...i keep on changing it so that i can recognize what it be exactly....

for the timing u can take it as 8x8...

m working on copy move forgery detection...

ur help means alot to me..

[Youssef Khmou]

ok thanks..

[Image Analyst]

Youssef, it's 8 by 8 because they chose to do so. I think intuitively you were expecting 256 by 256, right? That's what I would expect. But for whatever reason, they decided to make an 8 by 8 so the first row or column counts any pixel in the range 0-31 that is next to any other pixel with gray level 0-31, and so on.

[Youssef Khmou]

Mr "Image Analyst": yes,as it is "comatrix" of M(m,n) "refers/related" to either covariance (cross correlation) , or simple meaning of Comtarix, size expected was n-by-n or m-by-m .

But this approach makes sens , unless one is concerned about very tiny details of individual pixels, then he can write a code suitable for that . ok thanks for the explanation

Answer 3

[Youssef Khmou]

so you have two means : left hand side and right hand side ( reference : the link above ), lets take an example :

 I=imread('liftingbody.png'); 
 G=graycomatrix(I);
[m n]=size(G);

 GLCMl=0  % left 
 GLCMr=0; % right 

 for x=1:m
    for y=1:n
        GLCMl=GLCMl+x*G(x,y);
        GLCMr=GLCMr+y*G(x,y);

    end
end

it will give 1277276 and 1277165 , logical answer ?

[angel]

left and right hand side means???

u mean in two directions row wise and column wise right??? sir

tell me if i m correct or not?

[Youssef Khmou]

everyrthing is in the link angel :

i quote : " The left hand equation calculates the mean based on the reference pixels, i. It is also possible to calculate the mean using the neighbour pixels, j, as in the right hand equation. For the symmetrical GLCM, where each pixel in the window is counted once as a reference and once as a neighbour, the two values are identical."

[angel]

thank u so much...

ur help means alot to me...

:)