fisher vector学习笔记:http://blog.csdn.net/happyer88/article/details/46576379
fisher vector改进:http://blog.csdn.net/happyer88/article/details/46625639
使用vlfeat提取fisher vector的matlab 代码
% 读入图片
I = vl_impattern('roofs1') ;
I = single(vl_imdown(rgb2gray(I))) ;
% 设置bin大小
binSize = 8 ;
% sparse sift中bin大小是根据该层的高斯平滑的尺度sigma计算来的
% dense sift这里是设定binSize,反推sigma
magnif = 3 ;
% 对图像做高斯平滑
Is = vl_imsmooth(I, sqrt((binSize/magnif)^2 -