int ssab_curve( float x,
float *y,
float *table,
int size)
{
int x_idx;
int x_found;
float *ptr;
float x1, x2, y1, y2;
#define TABLE_Y(ix) (*(table + 2 * (ix) - 1))
#define TABLE_X(ix) (*(table + 2 * (ix) - 2))
/* Get the x point */
ptr = table;
x_found = 0;
for ( x_idx = 0; x_idx < size; x_idx++)
{
if ( *ptr > x)
{
x_found = 1;
break;
}
ptr += 2;
}
/* Interpolate */
if ( !x_found )
{
/* Take the very last point */
*y = TABLE_Y( size);
}
else if ( x_idx == 0 )
{
/* Take the first point */
*y = TABLE_Y( 1);
}
else
{
y1 = TABLE_Y( x_idx);
y2 = TABLE_Y( x_idx + 1);
x1 = TABLE_X( x_idx);
x2 = TABLE_X( x_idx + 1);
*y = y1 + ( y2 - y1) * (x - x1)/(x2 - x1);
}
return SUTL__SUCCESS;
}
static int
default_wcsmap_interpolate(struct wcsmap_param_t* m,
const double xd, const double yd,
const integer_t n,
double* xin /*[n]*/, double* yin /*[n]*/,
/* Output parameters */
double* xout, double* yout,
struct driz_error_t* error) {
int i;
int result = 1;
double *xiptr;
double *yiptr;
double *xoptr;
double *yoptr;
double *table;
double x, y;
int xi, yi;
double xf, yf, ixf, iyf;
double tabx00, tabx01, tabx10, tabx11;
/* do the bilinear interpolation */
xiptr = xin;
yiptr = yin;
xoptr = xout;
yoptr = yout;
table = m->table;
#define TABLE_X(x, y) (table[((y)*m->snx + (x))*2])
#define TABLE_Y(x, y) (table[((y)*m->snx + (x))*2 + 1])
for (i = 0; i < n; ++i) {
x = *xiptr++ / m->factor;
y = *yiptr++ / m->factor;
xi = (int)floor(x);
yi = (int)floor(y);
xf = x - (double)xi;
yf = y - (double)yi;
ixf = 1.0 - xf;
iyf = 1.0 - yf;
tabx00 = TABLE_X(xi, yi);
tabx10 = TABLE_X(xi+1, yi);
tabx01 = TABLE_X(xi, yi+1);
tabx11 = TABLE_X(xi+1, yi+1);
/* Account for interpolating across 360-0 boundary */
if ((tabx00 - tabx10) > 359) {
tabx00 -= 360.0;
tabx01 -= 360.0;
} else if ((tabx00 - tabx10) < -359) {
tabx10 -= 360.0;
tabx11 -= 360.0;
}
*xoptr++ =
tabx00 * ixf * iyf +
tabx10 * xf * iyf +
tabx01 * ixf * yf +
tabx11 * xf * yf;
*yoptr++ =
TABLE_Y(xi, yi) * ixf * iyf +
TABLE_Y(xi+1, yi) * xf * iyf +
TABLE_Y(xi, yi+1) * ixf * yf +
TABLE_Y(xi+1, yi+1) * xf * yf;
}
#undef TABLE_X
#undef TABLE_Y
result = 0;
exit:
return result;
}