/*----------------------------------------------------------------------------
                                  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 "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;
}



