Impala Documentation

Array2dScalarReal64* Impala::Core::Array::MakeGaussian2d	(	double	st,
		double	sr,
		double	phi,
		int	dert,
		double	n
	)			`[inline]`

Generate a kernel image resembling a Gaussian.

WARNING: jan-mark thinks it works only for 0th order and 2nd order mixed derivative

Definition at line 29 of file MakeGaussian2d.h.

References ABS, and M_PI.

Referenced by Impala::Core::KeyPoint::Sift::BuildGaussians(), GaussDerivative2d(), and Impala::Core::KeyPoint::Sift::Init().

00030 {
00031     int         xx, yy, width, height;
00032     double      l, divido;
00033 
00034     phi = phi*M_PI/180.0;
00035     if (phi == 0.0) {
00036         width  = (int)(n*st);
00037         height = (int)(n*sr);
00038     } else {
00039         l = sqrt(sr*sr/(cos(phi)*cos(phi)) + st*st/(sin(phi)*sin(phi)));
00040         width = (int)(n*ABS(st*st/tan(phi) + sr*sr*tan(phi))/l + 0.5);
00041         l = sqrt(st*st/(cos(phi)*cos(phi)) + sr*sr/(sin(phi)*sin(phi)));
00042         height = (int)(n*ABS(sr*sr/tan(phi) + st*st*tan(phi))/l + 0.5);
00043     }
00044     divido = 1./(2*M_PI*sr*st);
00045 
00046     double* fData = new double[(2*width+1) * (2*height+1)];
00047 
00048     int i=0;
00049     for (yy=0; yy<2*height+1; yy++) {
00050         for (xx=0; xx<2*width+1; xx++) {
00051             if (dert==2) {
00052                 divido = (pow((cos(phi)*(xx-width)+sin(phi)*(yy-height))/st,
00053                                         2.0)-1.)/(2*M_PI*sr*st*st);
00054             }
00055             fData[i] = (double)(divido * exp(-0.5 *
00056                 (pow(( cos(phi)*(xx-width)+sin(phi)*(yy-height))/st,2.0)+
00057                 pow((-sin(phi)*(xx-width)+cos(phi)*(yy-height))/sr,2.0))));
00058             i++;
00059         }
00060     }
00061     return ArrayCreate<Array2dScalarReal64>(2*width+1, 2*height+1, 0, 0, fData);
00062 }