// Prepare image (in-place) for cardinal spline interpolation.
bool prepare_spline(float *img, int w, int h, int pd, int order)
{
if(order < 3)
return true;
// Replace nans and infinities with 0
for (int i = 0; i < w * h * pd; i++)
if (!isfinite(img[i]))
img[i] = 0;
// Init poles of associated z-filter
double z[5];
if (! fill_poles(z, order))
return false;
int npoles = order / 2;
for (int k = 0; k < pd; k++) { // Loop on image components
for (int y = 0; y < h; y++) // Filter on lines
invspline1D(img + (y*w+0)*pd + k, pd * 1, w, z, npoles);
for (int x = 0; x < w; x++) // Filter on columns
invspline1D(img + (0*w+x)*pd + k, pd * w, h, z, npoles);
}
return true;
}
// Guoshen Yu, 2010.09.21, Windows version
void finvspline(vector<float> &in,int order,vector<float>& out, int width, int height)
// void finvspline(float *in,int order,float *out, int width, int height)
{
double *c,*d,z[5];
int npoles,nx,ny,x,y;
ny = height; nx = width;
/* initialize poles of associated z-filter */
switch (order)
{
case 2: z[0]=-0.17157288; /* sqrt(8)-3 */
break;
case 3: z[0]=-0.26794919; /* sqrt(3)-2 */
break;
case 4: z[0]=-0.361341; z[1]=-0.0137254;
break;
case 5: z[0]=-0.430575; z[1]=-0.0430963;
break;
case 6: z[0]=-0.488295; z[1]=-0.0816793; z[2]=-0.00141415;
break;
case 7: z[0]=-0.53528; z[1]=-0.122555; z[2]=-0.00914869;
break;
case 8: z[0]=-0.574687; z[1]=-0.163035; z[2]=-0.0236323; z[3]=-0.000153821;
break;
case 9: z[0]=-0.607997; z[1]=-0.201751; z[2]=-0.0432226; z[3]=-0.00212131;
break;
case 10: z[0]=-0.636551; z[1]=-0.238183; z[2]=-0.065727; z[3]=-0.00752819;
z[4]=-0.0000169828;
break;
case 11: z[0]=-0.661266; z[1]=-0.27218; z[2]=-0.0897596; z[3]=-0.0166696;
z[4]=-0.000510558;
break;
default:
printf("finvspline: order should be in 2..11.\n");
exit(-1);
}
npoles = order/2;
/* initialize double array containing image */
c = (double *)malloc(nx*ny*sizeof(double));
d = (double *)malloc(nx*ny*sizeof(double));
for (x=nx*ny;x--;)
c[x] = (double)in[x];
/* apply filter on lines */
for (y=0;y<ny;y++)
invspline1D(c+y*nx,nx,z,npoles);
/* transpose */
for (x=0;x<nx;x++)
for (y=0;y<ny;y++)
d[x*ny+y] = c[y*nx+x];
/* apply filter on columns */
for (x=0;x<nx;x++)
invspline1D(d+x*ny,ny,z,npoles);
/* transpose directy into image */
for (x=0;x<nx;x++)
for (y=0;y<ny;y++)
out[y*nx+x] = (float)(d[x*ny+y]);
/* free array */
free(d);
free(c);
}