Populating a matrix with pixel values

Hello everyone.

I have a question, and I hope that someone out there can help me out. I am trying to use for loops to populate a matrix with pixel values from a given image.

Given an image, and an x and y coordinate, I want to generate a 5x5 matrix centered on (x,y), populated by pixel intensity values from the image.

A sample of my code:

for a = 0:6
matrix(r,:)=image((y+2)-a, (x-2):(x+2));
a=a+1;
end

Where matrix is the 5x5 matrix that I am trying to generate.

As you can see from the above code, I want to generate a 5x5 matrix, populating each matrix row wise, with the pixel intensity of the image based upon changing the coordinates. However, whenever I run this section of code in MatLab, the error i receive says:

??? Error using ==> image
Incorrect number of arguments specified.

Error in ==> generatematrix at 21
clutter7(r,:)=image((y+3)-a,(x-3):(x+3));

I'm assuming that this message means that MatLab does not allow the image(x,y) command to retrieve information using the ':' operator. Am I wrong in this assumption? Does anybody knows if there is another way to automatically generate this matrix through the use of a for loop or some other operator?

.