get_subwindow.m

function out = get_subwindow(im, pos, model_sz, currentScaleFactor, cos_window, features)
%GET_SUBWINDOW Obtain sub-window from image, with replication-padding.
%   Returns sub-window of image IM centered at POS ([y, x] coordinates),
%   with size SZ ([height, width]). If any pixels are outside of the image,
%   they will replicate the values at the borders.
%
%   The subwindow is also normalized to range -0.5 .. 0.5, and the given
%   cosine window COS_WINDOW is applied (though this part could be omitted
%   to make the function more general).
%
%   Jo�o F. Henriques, 2012
%   http://www.isr.uc.pt/~henriques/

if isscalar(model_sz),  %square sub-window
    model_sz = [model_sz, model_sz];
end

patch_sz = floor(model_sz * currentScaleFactor);

%make sure the size is not to small
if patch_sz(1) < 1
    patch_sz(1) = 2;
end;
if patch_sz(2) < 1
    patch_sz(2) = 2;
end;


xs = floor(pos(2)) + (1:patch_sz(2)) - floor(patch_sz(2)/2);
ys = floor(pos(1)) + (1:patch_sz(1)) - floor(patch_sz(1)/2);

%check for out-of-bounds coordinates, and set them to the values at
%the borders
xs(xs < 1) = 1;
ys(ys < 1) = 1;
xs(xs > size(im,2)) = size(im,2);
ys(ys > size(im,1)) = size(im,1);

%extract image
im_patch = im(ys, xs, :);

%resize image to model size
im_patch = imresize(im_patch, model_sz, 'bilinear', 'AntiAliasing',false);
% im_patch = mexResize(im_patch, model_sz, 'auto');

% compute feature map
out = get_feature_map(im_patch);

%apply cosine window
out = bsxfun(@times, cos_window, out);
end