comp_mix_scales.m

Standard model object recognition matlab code

function y = comp_mix_scales (x, m, mix_f, type)

% FUNCTION y = comp_mix_scales (x, m, mix_f, type)
%
% We are going to mix scales by (1) resizing two different scales
% and (2) concatenating them and (3) using the mex file.  For
% example, suppose we would like to mix A = [1 1; 1 1] and 
% B = [2 2 2; 2 2 2; 2 2 2].  (1) Using aux_resize_3d, we resize A
% (or fit it to the larger matrix).  Now, A = [1 1 1; 1 1 1; 1 1
% 1].  (The resizing is done with nearest-neighbor approximation).
% (2) Concatenate A and B along the first dimension, so that 
% x_new = [1 1 1; 1 1 1; 1 1 1; 2 2 2; 2 2 2; 2 2 2].  Scale-mixing
% filter will be mx_f = [1; 0; 0; 1].  (3) x_new and mix_f can then
% be used with comp_get_next_layer.

y     = [];
x_new = [];

% The input m, mixing matrix, will have the same number of scales
% as the input, and the scales that are to be mixed will have the
% same integer values.  In other words, if we want to mix 8 scales
% in groups of twos, resulting in 4 scales, 
% m = [1 1 2 2 3 3 4 4];

num_scale = length(m);
for i = 1:num_scale
  scale_tag     = ['s' num2str(i)];
  old_size(i,:) = size(getfield(x, scale_tag));
end

for m_idx = 1:max(m) % loop thru all mixing

  % find the scales that are to be mixed
  which_scales = find(m == m_idx);
  num_s        = length(which_scales);

  % target size
  new_size     = max(old_size(which_scales,:),[],1);

  % we will mix scales by concatenating all relevant scales (in
  % which_scales), and then by creating a filter that
  % corresponds to them.
  x_tmp = zeros(new_size(1)*num_s, new_size(2), new_size(3));
  for i = 1:num_s
    scale_tag = ['s' num2str(which_scales(i))];
    curr_x    = getfield(x, scale_tag);
    curr_x    = aux_resize_3d(curr_x, new_size);
    x_tmp([1:new_size(1)]+(i-1)*new_size(1),:,:) = curr_x;
  end

  scale_tag = ['s' num2str(m_idx)];
  x_new     = setfield(x_new, scale_tag, x_tmp);
  
  % The scale-mixing filter was already created in filt_scalemixing
  % at some arbitrary size, so modify i1_s, according to the
  % correct size.
  where_ones = ([1:num_s]-1)*new_size(1)+1;
  i1_s  = repmat([where_ones'; 0], [1 new_size(3)]);
  siz_s = [max(where_ones) 1 new_size(3) new_size(3)];
  mix_f = setfield(mix_f, ['i1_' scale_tag], i1_s);
  mix_f = setfield(mix_f, ['size_' scale_tag], siz_s);
  
end

y = comp_get_next_layer (x_new, mix_f, type);