float* describe_point(const IplImage *src, t_point *pt, int &size) {
int offsetX[] = {1, 1, -1, -1};
int offsetY[] = {1, -1, 1, -1};
int radius = 2;
// float mag[(radius + 1) * (radius + 1) + 1];
// float ori[(radius + 1) * (radius + 1) + 1];
int _x = pt->x;
int _y = pt->y;
int x, y;
float _mag, _ori;
int bin_num = 8;
float *_hist = new float[bin_num * 4];
float *hist = _hist;
float sum;
//memset(hist, 0, sizeof(hist));
for (int i = 0; i < bin_num * 4; i++) hist[i] = 0;
for (int o = 0; o < 4; o++) {
x = offsetX[o] * radius + _x;
y = offsetY[o] * radius + _y;
hist = _hist + o * bin_num;
if (x < 0 || x >= src->width ||
y < 0 || y >= src->height)
continue;
for (int i = -radius; i <= radius; i++) {
for (int j = -radius; j <= radius; j++) {
//cout << x + i << " " << y + i << endl;
if (calc_grad_mag_ori(src, x + i, y + j, _mag, _ori)) {
int bin = cvRound(bin_num * (_ori + CV_PI) / (2 * CV_PI));
bin = bin < bin_num ? bin : 0;
int ai = ABS(i);
int aj = ABS(j);
hist[bin] += gauss[ai][aj] * _mag;
// cout << bin << endl;
// cout << gauss[ai][aj] * _mag << endl;
}
}
}
// cout << "----\n";
}
//cout << "****\n";
sum = 0.0;
for (int j = 0; j < bin_num * 4; j++) {
sum += _hist[j] * _hist[j];
}
for (int i = 0; i < bin_num * 4; i++) {
_hist[i] = _hist[i] / sum;
}
size = bin_num * 4;
return _hist;
}
/*
Computes a gradient orientation histogram at a specified pixel.
@param img image
@param r pixel row
@param c pixel col
@param n number of histogram bins
@param rad radius of region over which histogram is computed
@param sigma std for Gaussian weighting of histogram entries
@return Returns an n-element array containing an orientation histogram
representing orientations between 0 and 2 PI.
*/
double* ori_hist( IplImage* img, int r, int c, int n, int rad, double sigma)
{
double* hist;
double mag, ori, w, exp_denom, PI2 = CV_PI * 2.0;
int bin, i, j;
hist = (double* )calloc( n, sizeof( double ) );
exp_denom = 2.0 * sigma * sigma;
for( i = -rad; i <= rad; i++ )
for( j = -rad; j <= rad; j++ )
if( calc_grad_mag_ori( img, r + i, c + j, &mag, &ori ) )
{
w = exp( -( i*i + j*j ) / exp_denom );
bin = cvRound( n * ( ori + CV_PI ) / PI2 );
bin = ( bin < n )? bin : 0;
hist[bin] += w * mag;
}
return hist;
}
/*
Computes a gradient orientation histogram at a specified pixel.
@param img image
@param r pixel row
@param c pixel col
@param n number of histogram bins
@param rad radius of region over which histogram is computed
@param sigma std for Gaussian weighting of histogram entries
@return Returns an n-element array containing an orientation histogram
representing orientations between 0 and 2 PI.
*/
static double* ori_hist( IplImage* img, int r, int c, int n, int rad, double sigma)
{
double* hist;//直方图数组
double mag, ori, w, exp_denom, PI2 = CV_PI * 2.0;
int bin, i, j;
//为直方图数组分配空间，共n个元素，n是柱的个数
hist = calloc( n, sizeof( double ) );
exp_denom = 2.0 * sigma * sigma;
//遍历以指定点为中心的搜索区域
for( i = -rad; i <= rad; i++ )
for( j = -rad; j <= rad; j++ )
//计算指定点的梯度的幅值mag和方向ori，返回值为1表示计算成功
if( calc_grad_mag_ori( img, r + i, c + j, &mag, &ori ) )
{
w = exp( -( i*i + j*j ) / exp_denom );//该点的梯度幅值权重
bin = cvRound( n * ( ori + CV_PI ) / PI2 );//计算梯度的方向对应的直方图中的bin下标
bin = ( bin < n )? bin : 0;
hist[bin] += w * mag;//在直方图的某个bin中累加加权后的幅值
}
return hist;//返回直方图数组
}
