/* Copyright (C) 2001-2023 Artifex Software, Inc.
   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.

   Refer to licensing information at http://www.artifex.com or contact
   Artifex Software, Inc.,  39 Mesa Street, Suite 108A, San Francisco,
   CA 94129, USA, for further information.
*/


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

/* Forward references */
static void color_hsb_to_rgb(double h, double s, double b, float rgb[3]);
static void color_rgb_to_hsb(double r, double g, double 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_gstate * pgs, double h, double s, double 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_gstate * 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. */
static void
color_rgb_to_hsb(double r, double g, double 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. */
static void
color_hsb_to_rgb(double hue, double saturation, double 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. */
        double 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
    }
}