boblsturm@0: function [Y] = rot_kernel(kernel, deg)
boblsturm@0: 
boblsturm@0: N = size( kernel, 1 );
boblsturm@0: max_rots = 4*(N-1);
boblsturm@0: deg_per_rot = 360 / max_rots;
boblsturm@0: 
boblsturm@0: % deg = deg - mod( deg, deg_per_rot );
boblsturm@0: deg = deg_per_rot * ( round( deg / deg_per_rot ) );
boblsturm@0: num_of_rots = ceil( deg / deg_per_rot );
boblsturm@0: 
boblsturm@0: if num_of_rots < 1
boblsturm@0:     Y = kernel;
boblsturm@0:     return
boblsturm@0: else
boblsturm@0:     for r = 1:num_of_rots
boblsturm@0:         if mod( r, 2 ) == 0
boblsturm@0:             kernel = rot_outer_layer( kernel );
boblsturm@0:         else
boblsturm@0:             kernel = rot_inner_layer( kernel );
boblsturm@0:         end
boblsturm@0:     end
boblsturm@0: end
boblsturm@0: 
boblsturm@0: Y = kernel;
boblsturm@0: 
boblsturm@0: end
boblsturm@0: 
boblsturm@0: function [Y] = rot_outer_layer( A ) 
boblsturm@0:     dim = size( A, 1 );
boblsturm@0:     top = A( 1, : );
boblsturm@0:     right = A( 2:dim, dim )';
boblsturm@0:     bottom = fliplr( A( dim, 1:dim - 1 ) );
boblsturm@0:     left = fliplr( A( 2:dim - 1, 1 )' );
boblsturm@0:     shifted_layers = wshift('1D',[top,right,bottom,left],-1);
boblsturm@0:     
boblsturm@0:     top = shifted_layers( 1:length(top));
boblsturm@0:     last_ind = length( top );
boblsturm@0:     
boblsturm@0:     right = shifted_layers( last_ind + 1 : last_ind + length(right));
boblsturm@0:     last_ind = last_ind + length( right );
boblsturm@0:     
boblsturm@0:     bottom = shifted_layers( last_ind + 1 : last_ind + length(bottom));
boblsturm@0:     last_ind = last_ind + length( bottom );
boblsturm@0:     
boblsturm@0:     left = shifted_layers( last_ind + 1 : end );
boblsturm@0:     
boblsturm@0:     A( 1, : ) = top;
boblsturm@0:     A( 2:dim, dim ) = right';
boblsturm@0:     A( dim, 1:dim - 1 ) = fliplr( bottom );
boblsturm@0:     A( 2:dim - 1, 1 ) = fliplr( left' );
boblsturm@0:     
boblsturm@0:     Y = A;
boblsturm@0: end
boblsturm@0: 
boblsturm@0: function [Y] = rot_inner_layer( kernel )
boblsturm@0: %     dim = size( kernel, 1 );
boblsturm@0: %     if  dim < 2
boblsturm@0: %         Y = rot_outer_layer( kernel )
boblsturm@0: %         return;
boblsturm@0: %     else
boblsturm@0: %         Y = rot_inner_layer( kernel( 2:dim - 1, 2:dim - 1 ) )
boblsturm@0: %     end
boblsturm@0:     dim = size( kernel, 1 );
boblsturm@0:     
boblsturm@0:     if mod( dim / 2, 2 ) == 0
boblsturm@0:         max_rots = dim / 2 - 1;
boblsturm@0:     else
boblsturm@0:         max_rots = dim / 2 - 0.5;
boblsturm@0:     end
boblsturm@0:     
boblsturm@0:     low = 2;
boblsturm@0:     high = dim - 1;
boblsturm@0:     for i = 1:max_rots
boblsturm@0:         kernel( low:high, low:high ) = rot_outer_layer( kernel( low:high, low:high ) );
boblsturm@0:         low = low + 1;
boblsturm@0:         high = high - 1;
boblsturm@0:     end
boblsturm@0:     
boblsturm@0:     Y = kernel;
boblsturm@0: end