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/*----------------------------------------------------------------------------
libpamcolor.c
------------------------------------------------------------------------------
These are the library functions, which belong in the libnetpbm library,
that deal with colors in the PAM image format.
-----------------------------------------------------------------------------*/
/* See libpbm.c for the complicated explanation of this 32/64 bit file
offset stuff.
*/
#define _FILE_OFFSET_BITS 64
#define _LARGE_FILES
#include <limits.h>
#include "pm_c_util.h"
#include "pam.h"
#include "ppm.h"
tuple
pnm_parsecolor(const char * const colorname,
sample const maxval) {
tuple retval;
pixel color;
struct pam pam;
pam.len = PAM_STRUCT_SIZE(bytes_per_sample);
pam.depth = 3;
pam.maxval = maxval;
pam.bytes_per_sample = pnm_bytespersample(maxval);
retval = pnm_allocpamtuple(&pam);
color = ppm_parsecolor(colorname, maxval);
retval[PAM_RED_PLANE] = PPM_GETR(color);
retval[PAM_GRN_PLANE] = PPM_GETG(color);
retval[PAM_BLU_PLANE] = PPM_GETB(color);
return retval;
}
double pnm_lumin_factor[3] = {PPM_LUMINR, PPM_LUMING, PPM_LUMINB};
void
pnm_YCbCrtuple(tuple const tuple,
double * const YP,
double * const CbP,
double * const CrP) {
/*----------------------------------------------------------------------------
Assuming that the tuple 'tuple' is of tupletype RGB, return the
Y/Cb/Cr representation of the color represented by the tuple.
-----------------------------------------------------------------------------*/
int const red = (int)tuple[PAM_RED_PLANE];
int const grn = (int)tuple[PAM_GRN_PLANE];
int const blu = (int)tuple[PAM_BLU_PLANE];
*YP = (+ PPM_LUMINR * red + PPM_LUMING * grn + PPM_LUMINB * blu);
*CbP = (- 0.16874 * red - 0.33126 * grn + 0.50000 * blu);
*CrP = (+ 0.50000 * red - 0.41869 * grn - 0.08131 * blu);
}
void
pnm_YCbCr_to_rgbtuple(const struct pam * const pamP,
tuple const tuple,
double const Y,
double const Cb,
double const Cr,
int * const overflowP) {
double rgb[3];
unsigned int plane;
bool overflow;
rgb[PAM_RED_PLANE] = Y + 1.4022 * Cr + .5;
rgb[PAM_GRN_PLANE] = Y - 0.7145 * Cr - 0.3456 * Cb + .5;
rgb[PAM_BLU_PLANE] = Y + 1.7710 * Cb + .5;
overflow = FALSE; /* initial assumption */
for (plane = 0; plane < 3; ++plane) {
if (rgb[plane] > pamP->maxval) {
overflow = TRUE;
tuple[plane] = pamP->maxval;
} else if (rgb[plane] < 0.0) {
overflow = TRUE;
tuple[plane] = 0;
} else
tuple[plane] = (sample)rgb[plane];
}
if (overflowP)
*overflowP = overflow;
}
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