corr2 is too expensive

I used to use small input images for the second stage of finding bees. When I switched to original size(1600x1200) the program took minutes to compute the correlation between windows and the samples. This time I changed to use sum(abs(win - sample)) and threshold to different values of positive and negative samples.

positive threshold : negative

0.6 : 1.0
http://farm5.static.flickr.com/4072/4346608685_3b71a707ca_o.png


0.5 : 2.0
http://farm3.static.flickr.com/2790/4346608677_584043b1ed_o.png


0.8 : 2.5
http://farm3.static.flickr.com/2688/4346641775_1578dc4368_o.png


0.8 : 2.0
http://farm3.static.flickr.com/2680/4346641767_f43140b968_o.png


0.8 : 1.5
http://farm3.static.flickr.com/2793/4346641763_2bf8929ac8_o.png


0.8 : 1.0
http://farm3.static.flickr.com/2683/4346641759_81a2639058_o.png


0.7 : 1.0
http://farm5.static.flickr.com/4020/4346641757_152a94b63e_o.png


0.5 : 1.5
http://farm5.static.flickr.com/4047/4346641755_4f6edc29a3_o.png



In sampling phase I intentionally selected bees in a dirty background, for which affected bees in a clean background.