I have a grayscale image, but when I run glcm graycomatrix code there was an error

I run graycomatrix code in my grayscale image (pap smear image), but there was an error. When I use this code

GLCM = graycomatrix(A, 'Offset' , [0 1; -1 1; -1 0; -1 -1]);

I get this error

Error using graycomatrix
Expected input number 1, I, to be two-dimensional.

Error in graycomatrix>ParseInputs (line 260)
validateattributes(I,{'logical','numeric'},{'2d','real','nonsparse'}, ...

Error in graycomatrix (line 167)
[I, Offset, NL, GL, makeSymmetric] = ParseInputs(varargin{:});

Whereas that code could run smoothly in my grayscale fundus image. Could you help me? Thank you

[KALYAN ACHARJYA]

Can you attach the image? If not solved yet

[Zanetta Liu]

It was solved. Thank you for your comment

Answer 1

[Image Analyst]

The badly-named A is most likely not a gray scale image, even if it looks monochrome. It's probably an RGB image. Let's call it grayImage instead of A and use this:

grayImage = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage);
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Use weighted sum of ALL channels to create a gray scale image.
  grayImage = rgb2gray(grayImage);
  % ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
  % which in a typical snapshot will be the least noisy channel.
  % grayImage = grayImage(:, :, 2); % Take green channel.
end

See attached demo of GLCM.

[Zanetta Liu]

Now my problem was solved. Like what you say it turns out not a grayscale image. Thank you

[Image Analyst]

You're welcome. Thanks for Accepting the answer.