求研究过rob hess 的sift源码的解惑

[追风筝的少年]

这段生成特征点描述子的，exp_denom，rbin，cbin这些变量什么意思？
static double*** descr_hist( IplImage* img, int r, int c, double ori,
double scl, int d, int n )
{
double*** hist;
double cos_t, sin_t, hist_width, exp_denom, r_rot, c_rot, grad_mag,
grad_ori, w, rbin, cbin, obin, bins_per_rad, PI2 = 2.0 * CV_PI;
int radius, i, j;

hist = calloc( d, sizeof( double** ) );
for( i = 0; i < d; i++ )
{
hist[i] = calloc( d, sizeof( double* ) );
for( j = 0; j < d; j++ )
hist[i][j] = calloc( n, sizeof( double ) );
}

cos_t = cos( ori );
sin_t = sin( ori );
bins_per_rad = n / PI2;
exp_denom = d * d * 0.5;
hist_width = SIFT_DESCR_SCL_FCTR * scl;
radius = hist_width * sqrt(2) * ( d + 1.0 ) * 0.5 + 0.5;
for( i = -radius; i <= radius; i++ )
for( j = -radius; j <= radius; j++ )
{
/*
Calculate sample's histogram array coords rotated relative to ori.
Subtract 0.5 so samples that fall e.g. in the center of row 1 (i.e.
r_rot = 1.5) have full weight placed in row 1 after interpolation.
*/
c_rot = ( j * cos_t - i * sin_t ) / hist_width;
r_rot = ( j * sin_t + i * cos_t ) / hist_width;
rbin = r_rot + d / 2 - 0.5;
cbin = c_rot + d / 2 - 0.5;

if( rbin > -1.0 && rbin < d && cbin > -1.0 && cbin < d )
if( calc_grad_mag_ori( img, r + i, c + j, &grad_mag, &grad_ori ))
{
grad_ori -= ori;
while( grad_ori < 0.0 )
grad_ori += PI2;
while( grad_ori >= PI2 )
grad_ori -= PI2;

obin = grad_ori * bins_per_rad;
w = exp( -(c_rot * c_rot + r_rot * r_rot) / exp_denom );
interp_hist_entry( hist, rbin, cbin, obin, grad_mag * w, d, n );
}
}

return hist;
}

[Symfund]

这么多人都在搞图像识别？期待另一个高斯再现！