%?imgPathName:?圖片路徑及名稱
%?cell_size:?cell的長寬
%?nblock:?block的width及height包括的cell個數
%?overlap:?block重疊比例
%?angle:?180/360
%?bin_num:?方向bin的數目
%?weight_vote:?高斯加權投票

function?HOG?=?HOG（imgPathName?cell_size?nblock...????????????????????????%?計算圖像的HOG特征向量
???????????????overlap?angle?bin_num）

if?nargin<2
????cell_size=8;??????????????????????????????????????????????????????????????%?默認參數
????nblock=2;
????overlap=0.5;
????angle=180;
????bin_num=9;
elseif?nargin<6
????error（‘Input?parameters?are?not?enough.‘）;
end
?
Img?=?imread（imgPathName）;
if?size（Img3）?==?3
????G?=?rgb2gray（Img）;????????????????????????????????????????????????????????%?簡化計算，直接轉換成灰度圖像
else
????G?=?Img;
end
?
[height?width]?=?size（G）;

hx?=?[-101];????????????????????????????????????????????????????????????????%?計算x、y方向的梯度
hy?=?-hx‘;
grad_x?=?imfilter（double（G）hx）;
grad_y?=?imfilter（double（G）hy）;

grad_mag=sqrt（grad_x.^2+grad_y.^2）;???????????????????????????????????????????%?計算梯度的模長

index=?grad_x==0;?????????????????????????????????????????????????????????????%?計算梯度的方向
grad_x（index）=1e-5;
YX=grad_y./grad_x;
if?angle==180
????grad_angle=?（（atan（YX）+（pi/2））*180）./pi;
elseif?angle==360
????grad_angle=?（（atan2（grad_ygrad_x）+pi）.*180）./pi;
end
?
bin_angle=angle/bin_num;??????????????????????????????????????????????????????%?標定方向
grad_orient=ceil（grad_angle./bin_angle）;
?
block_size=cell_size*nblock;??????????????????????????????????????????????????%?計算block個數
skip_step=block_size*overlap;
x_step_num=floor（（width-block_size）/skip_step+1）;
y_step_num=floor（（height-block_size）/skip_step+1）;
?
feat_dim=bin_num*nblock^2;????????????????????????????????????????????????????%?初始化HOG特征描述子
HOG=zeros（feat_dimx_step_num*y_step_num）;
?
for?k=1:y_step_num
????for?j=1:x_step_num
????????x_off?=?（j-1）*skip_step+1;????????????????????????????????????????????%?block左上角坐標
????????y_off?=?（k-1）*skip_step+1;
?
????????b_mag=grad_mag（y_off:y_off+block_size-1x_off:x_off+block_size-1）;????%?獲取block梯度大小與方向
????????b_orient=grad_orient（y_off:y_off+block_size-1x_off:x_off+block_size-1）;
?
????????currFeat?=?BlkHOG（b_mag?b_orient?cell_sizenblock?bin_num?false）;?%?當前block的HOG
????????HOG（:?（k-1）*x_step_num+j）?=?currFeat;?
????end
end

function?BlkHOG?=?BlkHOG（?b_magb_orientcell_sizenblock...?????????????????%?計算單個block的HOG特征向量
??????????????????bin_num?weight_vote）

BlkHOG=zeros（bin_num*nblock^21）;

gaussian_weight=fspecial（‘gaussian‘cell_size*nblock0.5*cell_size*nblock）;???%?高斯權重

for?n=1:nblock????????????????????????????????????????????????????????????????%?分割block
????for?m=1:nblock
????????x_off?=?（m-1）*cell_size+1;????????????????????????????????????????????%?cell左上角坐標
????????y_off?=?（n-1）*cell_size+1;

????????c_mag=b_mag（y_off:y_off+cell_size-1x_off:x_off+cell_size-1）;?????????%?cell梯度大小與方向
????????c_orient=b_orient（y_off:y_off+cell_size-1x_off:x_off+cell_size-1）;
?
????????c_feat=zeros（bi

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????文件????????3828??2013-03-19?17:05??HOG.m