title: Image filtering without built in function matlab
body: <p>I need help for a function for filtering an image. I tried this:</p>
  
  <pre><code>originalImage = imread('A4.jpg');
  n = 100;
  resizedImage = imresize(originalImage, [n n]);
  
  figure;
  imshow(resizedImage);
  title('Original Bild');
  
  J = im2double(resizedImage);
  h1 = [1 1 1; 1 -8 1; 1 1 1];
  h2 = 1/16 * [1 2 1; 2 4 2; 1 2 1];
  h3 = [1 2 1; 0 0 0; -1 -2 -1];
  
  h1_180 = imrotate(h1, 180);
  h2_180 = imrotate(h2, 180);
  h3_180 = imrotate(h3, 180);
  J1 = padarray(J,[1 1]);
  
  for a =1:100
  J2= J1.* h1;   
  end
  
  figure;
  imshow(J2);
  title('Faltung mit h1');    
  </code></pre>
  
  <p>This is not working. What do I need ?</p>