how to segment image into 4 equivalent parts ?

how can I segment an image (brain) into 4 parts or 2 parts like the following figure ?

Answer 1

[Image Analyst]

Try this:

[rows, columns, numberOfColors] = size(yourImage);
midRow = round(rows/2);
midCol = round(columns/2);
upperLeft = yourImage(1:midRow, 1:midCol, :);
lowerLeft = yourImage(midRow+1:end, 1:midCol, :);
upperRight = yourImage(1:midRow, midCol+1:end, :);
lowerLeft = yourImage(midRow+1:end, midCol+1:end, :);
figure;
subplot(2, 2, 1);
imshow(upperLeft);
subplot(2, 2, 2);
imshow(lowerLeft);
subplot(2, 2, 3);
imshow(upperRight);
subplot(2, 2, 4);
imshow(lowerLeft);

[marwa za]

thanks