How do I make a 21x21 array from the center of a 200x150 array?

This image is 200x150. How do I create a 21x21 array from the center of the 200x150 array?

Answer 1

[Star Strider]

I called your image ‘parrot grayscale.png’.

I = imread('parrot grayscale.png');
[r,c] = size(I);
sr = fix((r-21)/2);
sc = fix((c-21)/2);

I2121 = I(sr:sr+20, sc:sc+20);
figure
imshow(I2121)

EDIT — Corrected typographical error. Code otherwise unchanged.

Answer 2

[Fabio Freschi]

% dimensions
n = 21;   % rows
m = 21;   % cols

% load image
A = imread('grayscale.png');

% find center coordinate
iCenter = round(size(A)/2);

% indices to save
iRow = iCenter(1)-floor(n/2)+(1:n);
jCol = iCenter(2)-floor(m/2)+(1:m);

% extraction
B = A(iRow,jCol);

% plot
figure
imshow(B)