image = imread('nemo.jpg');
buff = zeros(size(image)); %bufor obrazka po przetwrzaniu

mask = ...
[ -1, -1, -1
  -1, 8, -1
  -1, -1, -1 ]

n = size(mask)(1)  % rozmiar boku maski
offset = floor(n/2);

for x=1+offset:size(image,1)-offset
    for y=1+offset:size(image,2)-offset
        buff(x,y,1) = sum(sum( mask .* double( image(x-offset:x+offset, y-offset:y+offset, 1) ) ));
        buff(x,y,2) = sum(sum( mask .* double( image(x-offset:x+offset, y-offset:y+offset, 2) ) ));
        buff(x,y,3) = sum(sum( mask .* double( image(x-offset:x+offset, y-offset:y+offset, 3) ) ));
    end
end

%wyswietlanie
subplot(1,2,1)
imshow(image);
subplot(1,2,2);
imshow(uint8(buff));