added util functions

Author: rasmusbergpalm

util/im2patches.m

@@ -1,8 +1,11 @@
 function patches = im2patches(im,m,n)
+    assert(rem(size(im,1),m)==0)
+    assert(rem(size(im,2),n)==0)
+    
     patches = [];
-    for i=1:10:n
-        for u=1:10:m
-             patch = im(u:u+9,i:i+9);
+    for i=1:m:size(im,1)
+        for u=1:n:size(im,2)
+             patch = im(u:u+m-1,i:i+n-1);
              patches = [patches patch(:)];
         end
     end

util/whiten.m

@@ -1,6 +1,7 @@
-function [X] = whiten(X,fudgefactor)
-    X = bsxfun(@minus, X, mean(X));
-    A = X'*X;
-    [V,D] = eig(A);
-    X = X*V*diag(1./(diag(D)+fudgefactor).^(1/2))*V';
+function X = whiten(X, fudgefactor)
+    C = cov(X);
+    M = mean(X);
+    [V,D] = eig(C);
+    P = V * diag(sqrt(1./(diag(D) + fudgefactor))) * V';
+    X = bsxfun(@minus, X, M) * P;
 end