/* Copyright (C) 1992, 2000 Aladdin Enterprises.  All rights reserved.
  
  This software is provided AS-IS with no warranty, either express or
  implied.
  
  This software is distributed under license and may not be copied,
  modified or distributed except as expressly authorized under the terms
  of the license contained in the file LICENSE in this distribution.
  
  For more information about licensing, please refer to
  http://www.ghostscript.com/licensing/. For information on
  commercial licensing, go to http://www.artifex.com/licensing/ or
  contact Artifex Software, Inc., 101 Lucas Valley Road #110,
  San Rafael, CA  94903, U.S.A., +1(415)492-9861.
*/

/* $Id: gxdcconv.c,v 1.6 2002/08/22 07:12:29 henrys 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 == NULL ? k : pis->black_generation == NULL ? frac_0 :
	 gx_map_color_frac(pis, k, black_generation));
    signed_frac ucr =
	(pis == NULL ? k : 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]);
}