/* Copyright (C) 1992, 2000 artofcode LLC.  All rights reserved.
  
  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2 of the License, or (at your
  option) any later version.

  This program is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License along
  with this program; if not, write to the Free Software Foundation, Inc.,
  59 Temple Place, Suite 330, Boston, MA, 02111-1307.

*/

/*$Id: gxdcconv.c,v 1.3.6.1.2.1 2003/01/17 00:49:03 giles Exp $ */
/* Conversion between device color spaces for Ghostscript */
#include "gx.h"
#include "gsdcolor.h"		/* for gxcmap.h */
#include "gxdcconv.h"		/* interface */
#include "gxdevice.h"		/* for gxcmap.h */
#include "gxcmap.h"
#include "gxfarith.h"
#include "gxlum.h"
#include "gxistate.h"

/*
 * The CMYK to RGB algorithms specified by Adobe are, e.g.,
 *      R = 1.0 - min(1.0, C + K)
 *      C = max(0.0, min(1.0, 1 - R - UCR))
 * We got better results on displays with
 *      R = (1.0 - C) * (1.0 - K)
 *      C = max(0.0, min(1.0, 1 - R / (1 - UCR)))
 * For utmost compatibility, we offer the Adobe algorithms as an option:
 */
#define USE_ADOBE_CMYK_RGB

/* ------ Color space conversion ------ */

/* Only 4 of the 6 conversions are implemented here; */
/* the other 2 (Gray to RGB/CMYK) are trivial. */

/* Convert RGB to Gray. */
frac
color_rgb_to_gray(frac r, frac g, frac b, const gs_imager_state * pis)
{
    return (r * (unsigned long)lum_red_weight +
	    g * (unsigned long)lum_green_weight +
	    b * (unsigned long)lum_blue_weight +
	    (lum_all_weights / 2))
	/ lum_all_weights;
}

/* Convert RGB to CMYK. */
/* Note that this involves black generation and undercolor removal. */
void
color_rgb_to_cmyk(frac r, frac g, frac b, const gs_imager_state * pis,
		  frac cmyk[4])
{
    frac c = frac_1 - r, m = frac_1 - g, y = frac_1 - b;
    frac k = (c < m ? min(c, y) : min(m, y));

    /*
     * The default UCR and BG functions are pretty arbitrary,
     * but they must agree with the ones in gs_init.ps.
     */
    frac bg =
	(pis->black_generation == NULL ? frac_0 :
	 gx_map_color_frac(pis, k, black_generation));
    signed_frac ucr =
	(pis->undercolor_removal == NULL ? frac_0 :
	 gx_map_color_frac(pis, k, undercolor_removal));

    if (ucr == frac_1)
	cmyk[0] = cmyk[1] = cmyk[2] = 0;
    else if (ucr == frac_0)
	cmyk[0] = c, cmyk[1] = m, cmyk[2] = y;
    else {
#ifdef USE_ADOBE_CMYK_RGB
	/* C = max(0.0, min(1.0, 1 - R - UCR)), etc. */
	signed_frac not_ucr = (ucr < 0 ? frac_1 + ucr : frac_1);

	cmyk[0] = (c < ucr ? frac_0 : c > not_ucr ? frac_1 : c - ucr);
	cmyk[1] = (m < ucr ? frac_0 : m > not_ucr ? frac_1 : m - ucr);
	cmyk[2] = (y < ucr ? frac_0 : y > not_ucr ? frac_1 : y - ucr);
#else
	/* C = max(0.0, min(1.0, 1 - R / (1 - UCR))), etc. */
	float denom = frac2float(frac_1 - ucr);		/* unscaled */
	float v;

	v = (float)frac_1 - r / denom;	/* unscaled */
	cmyk[0] =
	    (is_fneg(v) ? frac_0 : v >= (float)frac_1 ? frac_1 : (frac) v);
	v = (float)frac_1 - g / denom;	/* unscaled */
	cmyk[1] =
	    (is_fneg(v) ? frac_0 : v >= (float)frac_1 ? frac_1 : (frac) v);
	v = (float)frac_1 - b / denom;	/* unscaled */
	cmyk[2] =
	    (is_fneg(v) ? frac_0 : v >= (float)frac_1 ? frac_1 : (frac) v);
#endif
    }
    cmyk[3] = bg;
    if_debug7('c', "[c]RGB 0x%x,0x%x,0x%x -> CMYK 0x%x,0x%x,0x%x,0x%x\n",
	      r, g, b, cmyk[0], cmyk[1], cmyk[2], cmyk[3]);
}

/* Convert CMYK to Gray. */
frac
color_cmyk_to_gray(frac c, frac m, frac y, frac k, const gs_imager_state * pis)
{
    frac not_gray = color_rgb_to_gray(c, m, y, pis);

    return (not_gray > frac_1 - k ?	/* gray + k > 1.0 */
	    frac_0 : frac_1 - (not_gray + k));
}

/* Convert CMYK to RGB. */
void
color_cmyk_to_rgb(frac c, frac m, frac y, frac k, const gs_imager_state * pis,
		  frac rgb[3])
{
    switch (k) {
	case frac_0:
	    rgb[0] = frac_1 - c;
	    rgb[1] = frac_1 - m;
	    rgb[2] = frac_1 - y;
	    break;
	case frac_1:
	    rgb[0] = rgb[1] = rgb[2] = frac_0;
	    break;
	default:
	    {
#ifdef USE_ADOBE_CMYK_RGB
		/* R = 1.0 - min(1.0, C + K), etc. */
		frac not_k = frac_1 - k;

		rgb[0] = (c > not_k ? frac_0 : not_k - c);
		rgb[1] = (m > not_k ? frac_0 : not_k - m);
		rgb[2] = (y > not_k ? frac_0 : not_k - y);
#else
		/* R = (1.0 - C) * (1.0 - K), etc. */
		ulong not_k = frac_1 - k;

		/* Compute not_k * (frac_1 - v) / frac_1 efficiently. */
		ulong prod;

#define deduct_black(v)\
  (prod = (frac_1 - (v)) * not_k, frac_1_quo(prod))
		rgb[0] = deduct_black(c);
		rgb[1] = deduct_black(m);
		rgb[2] = deduct_black(y);
#undef deduct_black
#endif
	    }
    }
    if_debug7('c', "[c]CMYK 0x%x,0x%x,0x%x,0x%x -> RGB 0x%x,0x%x,0x%x\n",
	      c, m, y, k, rgb[0], rgb[1], rgb[2]);
}