/*
* R T _ S P E C T _ M A K E _ N T S C _ R G B
*
* Using the "Representative set of camera taking sensitivities"
* for a NTSC television camera, from Benson "Television Engineering
* Handbook" page 4.58, convert an RGB value in range 0..1 to
* a spectral curve also in range 0..1.
*
* These curves should be used in converting spectral samples
* to NTSC RGB values.
*/
void
spect_make_NTSC_RGB(struct bn_tabdata **rp,
struct bn_tabdata **gp,
struct bn_tabdata **bp,
const struct bn_table *tabp)
{
BN_CK_TABLE(tabp);
/* Convert array of number pairs into bn_tabdata & bn_table */
rt_NTSC_r_tabdata = bn_tabdata_from_array(&rt_NTSC_R[0][0]);
rt_NTSC_g_tabdata = bn_tabdata_from_array(&rt_NTSC_G[0][0]);
rt_NTSC_b_tabdata = bn_tabdata_from_array(&rt_NTSC_B[0][0]);
bu_log("ntsc_R: area=%g\n", bn_tabdata_area2(rt_NTSC_r_tabdata));
bn_print_table_and_tabdata("/dev/tty", rt_NTSC_r_tabdata);
bu_log("ntsc_G: area=%g\n", bn_tabdata_area2(rt_NTSC_g_tabdata));
bn_print_table_and_tabdata("/dev/tty", rt_NTSC_g_tabdata);
bu_log("ntsc_B: area=%g\n", bn_tabdata_area2(rt_NTSC_b_tabdata));
bn_print_table_and_tabdata("/dev/tty", rt_NTSC_b_tabdata);
/* Resample original NTSC curves to match given bn_table sampling */
#if 0
/* just to test the routine */
*rp = bn_tabdata_resample_avg(tabp, rt_NTSC_r_tabdata);
*gp = bn_tabdata_resample_avg(tabp, rt_NTSC_g_tabdata);
*bp = bn_tabdata_resample_avg(tabp, rt_NTSC_b_tabdata);
#else
/* use this one for real */
*rp = bn_tabdata_resample_max(tabp, rt_NTSC_r_tabdata);
*gp = bn_tabdata_resample_max(tabp, rt_NTSC_g_tabdata);
*bp = bn_tabdata_resample_max(tabp, rt_NTSC_b_tabdata);
#endif
}
/*
* R T _ S P E C T _ C U R V E _ T O _ X Y Z
*
* Convenience routine.
* Serves same function as Roy Hall's CLR_spect_to_xyz(), pg 233.
* The normalization xyz_scale = 1.0 / bn_tabdata_area2(cie_y);
* has been folded into spect_make_CIE_XYZ();
*/
void
spect_curve_to_xyz(point_t xyz,
const struct bn_tabdata *tabp,
const struct bn_tabdata *cie_x,
const struct bn_tabdata *cie_y,
const struct bn_tabdata *cie_z)
{
fastf_t tab_area;
BN_CK_TABDATA(tabp);
#if 0
tab_area = bn_tabdata_area2(tabp);
bu_log(" tab_area = %g\n", tab_area);
if (fabs(tab_area) < VDIVIDE_TOL) {
bu_log("spect_curve_to_xyz(): Area = 0 (no luminance) in this part of the spectrum\n");
VSETALL(xyz, 0);
return;
}
tab_area = 1 / tab_area;
#else
/* This is what Roy says to do, but I'm not certain */
tab_area = 1;
#endif
xyz[X] = bn_tabdata_mul_area2(tabp, cie_x) * tab_area;
xyz[Y] = bn_tabdata_mul_area2(tabp, cie_y) * tab_area;
xyz[Z] = bn_tabdata_mul_area2(tabp, cie_z) * tab_area;
}
static int
test_bn_tabdata_area2(int argc, char *argv[])
{
struct bn_table *tab_in;
struct bn_tabdata *td_in;
fastf_t expected, actual;
if (argc != 5) {
bu_exit(1, "<args> format: table tabdata expected_result [%s]\n", argv[0]);
}
scan_tab_args(argv[2], &tab_in);
scan_tabdata_args(argv[3], &td_in, tab_in);
sscanf(argv[4], "%lg", &expected);
actual = bn_tabdata_area2(td_in);
bu_log("Result: %g\n", actual);
return !NEAR_EQUAL(expected, actual, BN_TOL_DIST);
}
/**
* R T _ S P E C T _ M A K E _ C I E _ X Y Z
*
* Given as input a spectral sampling distribution, generate the 3
* curves to match the human eye's response in CIE color parameters X,
* Y, and Z. XYZ space can be readily converted to RGB with a 3x3
* matrix.
*
* The tabulated data is linearly interpolated.
*
* Pointers to the three spectral weighting functions are "returned",
* storage for the X, Y, and Z curves is allocated by this routine and
* must be freed by the caller.
*/
void
rt_spect_make_CIE_XYZ(struct bn_tabdata **x, struct bn_tabdata **y, struct bn_tabdata **z, const struct bn_table *tabp)
{
struct bn_tabdata *a, *b, *c;
fastf_t xyz_scale;
int i;
int j;
BN_CK_TABLE(tabp);
i = bn_table_interval_num_samples( tabp, 430., 650. );
if ( i <= 4 ) bu_log("rt_spect_make_CIE_XYZ: insufficient samples (%d) in visible band\n", i);
BN_GET_TABDATA( a, tabp );
BN_GET_TABDATA( b, tabp );
BN_GET_TABDATA( c, tabp );
*x = a;
*y = b;
*z = c;
/* No CIE data below 380 nm */
for ( j=0; tabp->x[j] < 380 && j < tabp->nx; j++ ) {
a->y[j] = b->y[j] = c->y[j] = 0;
}
/* Traverse the CIE table. Produce as many output values as
* possible before advancing to next CIE table entry.
*/
for ( i = 0; i < 81-1; i++ ) {
fastf_t fract; /* fraction from [i] to [i+1] */
again:
if ( j >= tabp->nx ) break;
if ( tabp->x[j] < rt_CIE_XYZ[i][0] ) bu_bomb("rt_spect_make_CIE_XYZ assertion1 failed\n");
if ( tabp->x[j] >= rt_CIE_XYZ[i+1][0] ) continue;
/* The CIE table has 5nm spacing */
fract = (tabp->x[j] - rt_CIE_XYZ[i][0] ) / 5;
if ( fract < 0 || fract > 1 ) bu_bomb("rt_spect_make_CIE_XYZ assertion2 failed\n");
a->y[j] = (1-fract) * rt_CIE_XYZ[i][1] + fract * rt_CIE_XYZ[i+1][1];
b->y[j] = (1-fract) * rt_CIE_XYZ[i][2] + fract * rt_CIE_XYZ[i+1][2];
c->y[j] = (1-fract) * rt_CIE_XYZ[i][3] + fract * rt_CIE_XYZ[i+1][3];
j++;
goto again;
}
/* No CIE data above 780 nm */
for (; j < tabp->nx; j++ ) {
a->y[j] = b->y[j] = c->y[j] = 0;
}
/* Normalize the curves so that area under Y curve is 1.0 */
xyz_scale = bn_tabdata_area2( b );
if ( fabs(xyz_scale) < VDIVIDE_TOL ) {
bu_log("rt_spect_make_CIE_XYZ(): Area = 0 (no luminance) in this part of the spectrum, skipping normalization step\n");
return;
}
xyz_scale = 1 / xyz_scale;
bn_tabdata_scale( a, a, xyz_scale );
bn_tabdata_scale( b, b, xyz_scale );
bn_tabdata_scale( c, c, xyz_scale );
}
