aux_palette.cpp

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/*
 * Vega Strike
 * Copyright (C) 2001-2002 Daniel Horn
 *
 * http://vegastrike.sourceforge.net/
 *
 * 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, USA.
 */
#include <math.h>
#define UNDEFINED -99999

double Maximum( double r, double g, double b )
{
    if (r > g && r > b)
        return r;
    if (b > r && b > g)
        return b;
    return g;
}

double Minimum( double r, double g, double b )
{
    if (r < g && r < b)
        return r;
    if (b < r && b < g)
        return b;
    return g;
}

void RGB_To_HSV( double r, double g, double b, double *h, double *s, double *v )
{
/*
 * given: rgb, each in [0,1]
 * desired: h in [0,360), s and v in [0,1] except if s = 0 then h = undefined
 */
    double max = Maximum( r, g, b );
    double min = Minimum( r, g, b );
    *v = max;                           /*This is the value v. */
    /* Next calculate saturation, s. Saturation is 0 if red, green and blue are all 0 */
    *s = (max != 0.0) ? ( (max-min)/max ) : 0.0;
    if (*s == 0.0) {
        *h = UNDEFINED;
    } else {
        /*Chromatic case: Saturation is not 0*/
        double delta = max-min;           /*Determine Hue*/
        if (r == max)
            *h = (g-b)/delta;                  /* resulting color is between yellow and magenta */
        else if (g == max)
            *h = 2.0+(b-r)/delta;                    /* resulting color is between cyan and yellow */
        else if (b == max)
            *h = 4.0+(r-g)/delta;                   /* resulting color is between magenta and cyan */
        *h *= 60.0;                             /*convert hue to degrees*/
        if (*h < 0.0)
            *h += 360.0;                        /*make sure its not negative*/
    }
}

void HSV_To_RGB( double *r, double *g, double *b, double h, double s, double v )
{
    if (s == 0.0) {
        /*
         * the color is on the black and white center line.
         *******************************achromatic color: there is no hue.
         */
        if (h == UNDEFINED) {
            *r = v;             /* this is the achromatic case. */
            *g = v;
            *b = v;
        } else {
            *r = v;             /* this is the achromatic case. */
            *g = v;
            *b = v;
        }
    } else {
        double f, p, q, t;         /*chromatic color: s != 0, so there is a hue*/
        int    i;
        if (h == 360.0)          /*360 degrees is equivalent to 0 degrees. */
            h = 0.0;
        h /= 60.0;         /* h is now in [0,6).*/
        i  = (int) (h);           /*Floor returns the greatest integer <= h*/
        f  = h-i;               /*f is the fractional part of h.*/
        p  = v*(1.0-s);
        q  = v*( 1.0-(s*f) );
        t  = v*( 1.0-( s*(1.0-f) ) );
        switch (i)
        {
        case 0:
            *r = v;
            *g = t;
            *b = p;
            break;
        case 1:
            *r = q;
            *g = v;
            *b = p;
            break;
        case 2:
            *r = p;
            *g = v;
            *b = t;
            break;
        case 3:
            *r = p;
            *g = q;
            *b = v;
            break;
        case 4:
            *r = t;
            *g = p;
            *b = v;
            break;
        case 5:
            *r = v;
            *g = p;
            *b = q;
            break;
        }
    }     /*Chromatic case */
}

//desired: h in [0,360), s and v in [0,1] except if s = 0 then h = undefined
void ShiftPalette( unsigned char Palette[769], double DH, double DS, double DV, double DsH, double DsS, double DsV )
{
    double r, g, b, h, s, v;
    int    i;
    for (i = 192; i < 224; i++) {
        r  = ( (double) .003921568627 )*Palette[i*3];
        g  = ( (double) .003921568627 )*Palette[i*3+1];
        b  = ( (double) .003921568627 )*Palette[i*3+2];
        RGB_To_HSV( r, g, b, &h, &s, &v );
        h += DH;
        s += DS;
        v += DV;
        if (h >= 360)
            h -= 360;
        if (h < 0)
            h += 360;
        if (s > 1)
            s -= 1;
        if (s < 0)
            s += 1;
        if (s == 0)
            s += .01;
        if (v > 1)
            v -= 1;
        if (v < 0)
            v += 1;
        HSV_To_RGB( &r, &g, &b, h, s, v );
        Palette[i*3]   = (unsigned char) (r*255);
        Palette[i*3+1] = (unsigned char) (g*255);
        Palette[i*3+2] = (unsigned char) (b*255);
    }
    for (i = 224; i < 256; i++) {
        r  = ( (double) .003921568627 )*Palette[i*3];
        g  = ( (double) .003921568627 )*Palette[i*3+1];
        b  = ( (double) .003921568627 )*Palette[i*3+2];
        RGB_To_HSV( r, g, b, &h, &s, &v );
        h += DsH;
        s += DsS;
        v += DsV;
        if (h >= 360)
            h -= 360;
        if (h < 0)
            h += 360;
        if (s > 1)
            s -= 1;
        if (s < 0)
            s += 1;
        if (s == 0)
            s += .01;
        if (v > 1)
            v -= 1;
        if (v < 0)
            v += 1;
        HSV_To_RGB( &r, &g, &b, h, s, v );
        Palette[i*3]   = (unsigned char) (r*255);
        Palette[i*3+1] = (unsigned char) (g*255);
        Palette[i*3+2] = (unsigned char) (b*255);
    }
}