HOGPicture speedup

[rosenfeldamir]

Hi,
I've re-implemented HOGPicture to be much faster, using a single matrix multiplication.
I think this should be in the main branch, and I don't know what would happen if I simply fork the project as is the default behavior;
So check it out - it's really useful (just copy & paste instead of the original code...)

---

function im = HOGpicture(w, bs)
%NOTE(TJM): I fixed a visualization bug which would sometimes show
%funky artifacts because pedro's version shows only the orientations
%facing one way. On synthetic images of squares this could be
%seen. The simple fix is to scan over 18 orientations not 9 when
%creating the histogram pics.

% Modified to vectorized version by Amir Rosenfeld, July 31st, 2012

if ~exist('bs','var')
bs = 20;
end
% HOGpicture(w, bs)
% Make picture of positive HOG weights.

% construct a "glyph" for each orientaion
s = size(w);
w(w<0) = 0;
bim1 = zeros(bs, bs);
bim1(:,round(bs/2):round(bs/2)+1) = 1;
bim = zeros([size(bim1) 9]);
bim(:,:,1) = bim1;
for i = 2:9,
bim(:,:,i) = imrotate(bim1, -(i-1)*20, 'crop');
end

bim = cat(3,bim,bim);
bim_ = reshape(bim,[],18);

B = im2col( zeros(bs_s(1), bs_s(2)),[bs bs],'distinct');
w_ = reshape(w(:,:,1:18),[],18);
im = col2im(bim__w_',[bs bs],[bs_s(1), bs*s(2)],'distinct');

end

[quantombone]

Sweet, Let me check this out, and I will push this into the main branch once I make sure it doesn't break anything! Will let you know once the change is made or if I have any questions