/*
Adds features to an array for every orientation in a histogram greater than a specified threshold.
@param features new features are added to the end of this array
@param hist orientation histogram
@param n number of bins in hist
@param mag_thr new features are added for entries in hist greater than this
@param feat new features are clones of this with different orientations
*/
static void add_good_ori_features( CvSeq* features, double* hist, int n,
double mag_thr, struct feature* feat )
{
struct feature* new_feat;
double bin, PI2 = CV_PI * 2.0;
int l, r, i;
//遍历直方图
for( i = 0; i < n; i++ )
{
l = ( i == 0 )? n - 1 : i-1;//前一个(左边的)bin的下标
r = ( i + 1 ) % n;//后一个(右边的)bin的下标
//若当前的bin是局部极值(比前一个和后一个bin都大)，并且值大于给定的幅值阈值，则新生成一个特征点并添加到特征点序列末尾
if( hist[i] > hist[l] && hist[i] > hist[r] && hist[i] >= mag_thr )
{
//根据左、中、右三个bin的值对当前bin进行直方图插值
bin = i + interp_hist_peak( hist[l], hist[i], hist[r] );
bin = ( bin < 0 )? n + bin : ( bin >= n )? bin - n : bin;//将插值结果规范到[0,n]内
new_feat = clone_feature( feat );//克隆当前特征点为新特征点
new_feat->ori = ( ( PI2 * bin ) / n ) - CV_PI;//新特征点的方向
cvSeqPush( features, new_feat );//插入到特征点序列末尾
free( new_feat );
}
}
}
/*
Adds features to an array for every orientation in a histogram greater than
a specified threshold.
@param features new features are added to the end of this array
@param hist orientation histogram
@param n number of bins in hist
@param mag_thr new features are added for entries in hist greater than this
@param feat new features are clones of this with different orientations
*/
void add_good_ori_features( CvSeq* features, double* hist, int n,
double mag_thr, struct feature* feat )
{
struct feature* new_feat;
double bin, PI2 = CV_PI * 2.0;
int l, r, i;
for( i = 0; i < n; i++ )
{
l = ( i == 0 )? n - 1 : i-1;
r = ( i + 1 ) % n;
if( hist[i] > hist[l] && hist[i] > hist[r] && hist[i] >= mag_thr )
{
bin = i + interp_hist_peak( hist[l], hist[i], hist[r] );
bin = ( bin < 0 )? n + bin : ( bin >= n )? bin - n : bin;
new_feat = clone_feature( feat );
new_feat->ori = ( ( PI2 * bin ) / n ) - CV_PI;
cvSeqPush( features, new_feat );
free( new_feat );
}
}
}