/* Copyright (C) 1994, 1997, 1998 Aladdin Enterprises.  All rights reserved.

   This file is part of Aladdin Ghostscript.

   Aladdin Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author
   or distributor accepts any responsibility for the consequences of using it,
   or for whether it serves any particular purpose or works at all, unless he
   or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
   License (the "License") for full details.

   Every copy of Aladdin Ghostscript must include a copy of the License,
   normally in a plain ASCII text file named PUBLIC.  The License grants you
   the right to copy, modify and redistribute Aladdin Ghostscript, but only
   under certain conditions described in the License.  Among other things, the
   License requires that the copyright notice and this notice be preserved on
   all copies.
 */

/*$Id: gshsb.c $ */
/* HSB color operators for Ghostscript library */
#include "gx.h"
#include "gscolor.h"
#include "gshsb.h"		/* interface definition */
#include "gxfrac.h"

/* Forward references */
private void color_hsb_to_rgb(P4(floatp h, floatp s, floatp b, float rgb[3]));
private void color_rgb_to_hsb(P4(floatp r, floatp g, floatp b, float hsb[3]));

/* Force a parameter into the range [0.0..1.0]. */
#define force_unit(p) (p < 0.0 ? 0.0 : p > 1.0 ? 1.0 : p)

/* sethsbcolor */
int
gs_sethsbcolor(gs_state * pgs, floatp h, floatp s, floatp b)
{
    float rgb[3];

    color_hsb_to_rgb(force_unit(h), force_unit(s), force_unit(b), rgb);
    return gs_setrgbcolor(pgs, rgb[0], rgb[1], rgb[2]);
}

/* currenthsbcolor */
int
gs_currenthsbcolor(const gs_state * pgs, float pr3[3])
{
    float rgb[3];

    gs_currentrgbcolor(pgs, rgb);
    color_rgb_to_hsb(rgb[0], rgb[1], rgb[2], pr3);
    return 0;
}

/* ------ Internal routines ------ */

/* Note: the color model conversion algorithms are taken from */
/* Rogers, Procedural Elements for Computer Graphics, pp. 401-403. */

/* Convert RGB to HSB. */
private void
color_rgb_to_hsb(floatp r, floatp g, floatp b, float hsb[3])
{
    frac red = float2frac(r), green = float2frac(g), blue = float2frac(b);

#define rhue hsb[0]
#define rsat hsb[1]
#define rbri hsb[2]
    if (red == green && green == blue) {
	rhue = 0;		/* arbitrary */
	rsat = 0;
	rbri = r;		/* pick any one */
    } else {			/* Convert rgb to hsb */
	frac V, Temp, diff;
	long H;

	V = (red > green ? red : green);
	if (blue > V)
	    V = blue;
	Temp = (red > green ? green : red);
	if (blue < Temp)
	    Temp = blue;
	diff = V - Temp;
	if (V == red)
	    H = (green - blue) * frac_1_long / diff;
	else if (V == green)
	    H = (blue - red) * frac_1_long / diff + 2 * frac_1_long;
	else			/* V == blue */
	    H = (red - green) * frac_1_long / diff + 4 * frac_1_long;
	if (H < 0)
	    H += 6 * frac_1_long;
	rhue = H / (frac_1 * 6.0);
	rsat = diff / (float)V;
	rbri = frac2float(V);
    }
#undef rhue
#undef rsat
#undef rbri
}

/* Convert HSB to RGB. */
private void
color_hsb_to_rgb(floatp hue, floatp saturation, floatp brightness, float rgb[3])
{
    if (saturation == 0) {
	rgb[0] = rgb[1] = rgb[2] = brightness;
    } else {			/* Convert hsb to rgb. */
	/* We rely on the fact that the product of two */
	/* fracs fits into an unsigned long. */
	floatp h6 = hue * 6;
	ulong V = float2frac(brightness);	/* force arithmetic to long */
	frac S = float2frac(saturation);
	int I = (int)h6;
	ulong F = float2frac(h6 - I);	/* ditto */

	/* M = V*(1-S), N = V*(1-S*F), K = V*(1-S*(1-F)) = M-N+V */
	frac M = V * (frac_1_long - S) / frac_1_long;
	frac N = V * (frac_1_long - S * F / frac_1_long) / frac_1_long;
	frac K = M - N + V;
	frac R, G, B;

	switch (I) {
	    default:
		R = V;
		G = K;
		B = M;
		break;
	    case 1:
		R = N;
		G = V;
		B = M;
		break;
	    case 2:
		R = M;
		G = V;
		B = K;
		break;
	    case 3:
		R = M;
		G = N;
		B = V;
		break;
	    case 4:
		R = K;
		G = M;
		B = V;
		break;
	    case 5:
		R = V;
		G = M;
		B = N;
		break;
	}
	rgb[0] = frac2float(R);
	rgb[1] = frac2float(G);
	rgb[2] = frac2float(B);
#ifdef DEBUG
	if (gs_debug_c('c')) {
	    dlprintf7("[c]hsb(%g,%g,%g)->VSFI(%ld,%d,%ld,%d)->\n",
		      hue, saturation, brightness, V, S, F, I);
	    dlprintf6("   RGB(%d,%d,%d)->rgb(%g,%g,%g)\n",
		      R, G, B, rgb[0], rgb[1], rgb[2]);
	}
#endif
    }
}
