a_colors.cxx

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/*
         Copyright 2002-2014 Pierre SMARS (smars@yuntech.edu.tw)
         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, see <http://www.gnu.org/licenses/>.
*/
#include <iostream>
#include <math.h>
#include "a_colors.h"
namespace a_colors
{
        //---------------------------------------------------------------------------
        double min(double a, double b)
        {
                if (a<b)
                        return a;
                else
                        return b;
        }
        //---------------------------------------------------------------------------
        double max(double a, double b)
        {
                return -(a_colors::min(-a,-b));
        }
        //---------------------------------------------------------------------------
        double min(double a, double b, double c)
        {
                return min(min(a,b),c);
        }
        //---------------------------------------------------------------------------
        double max(double a, double b, double c)
        {
                return max(max(a,b),c);
        }
        //---------------------------------------------------------------------------
        void cmy2rgb(double C, double M, double Y, double& R, double& G, double&B)
        {
                R = int(255*(1.-C)+.5);
                G = int(255*(1.-M)+.5);
                B = int(255*(1.-Y)+.5);
        }
        //---------------------------------------------------------------------------
        void cmyk2cmy(double C, double M, double Y, double K, double& Cn, double& Mn, double&Yn)
        {
                Cn = C*(1.-K);
                Mn = M*(1.-K);
                Yn = Y*(1.-K);
        }
        //---------------------------------------------------------------------------
        void rgb2hsv(double R, double G, double B, double& H, double& S, double&V)
        {
                double var_R = ( R / 255 );                     //RGB values = 0 ÷ 255
                double var_G = ( G / 255 );
                double var_B = ( B / 255 );
 
                double var_Min = min( var_R, var_G, var_B );    //Min. value of RGB
                double var_Max = max( var_R, var_G, var_B );    //Max. value of RGB
                double del_Max = var_Max - var_Min;             //Delta RGB value
 
                V = var_Max;
 
                if ( del_Max == 0 )                     //This is a gray, no chroma...
                {
                        H = 0;                               //HSV results = 0 ÷ 1
                        S = 0;
                }
                else                                    //Chromatic data...
                {
                        S = del_Max / var_Max;
 
                        double del_R = ( ( ( var_Max - var_R ) / 6. ) + ( del_Max / 2. ) ) / del_Max;
                        double del_G = ( ( ( var_Max - var_G ) / 6. ) + ( del_Max / 2. ) ) / del_Max;
                        double del_B = ( ( ( var_Max - var_B ) / 6. ) + ( del_Max / 2. ) ) / del_Max;
 
                        if      ( var_R == var_Max ) H = del_B - del_G;
                        else if ( var_G == var_Max ) H = ( 1. / 3. ) + del_R - del_B;
                        else if ( var_B == var_Max ) H = ( 2. / 3. ) + del_G - del_R;
                        if ( H < 0. ) H += 1.;
                        if ( H > 1. ) H -= 1.;
                }
        }
        //---------------------------------------------------------------------------
        void hsv2rgb(double H, double S, double V, double& R, double& G, double&B)
        {
                if (S==0)
                {
                        S *= 255;
                        R = G = B = fabs(S);
                        return;
                }
                if (H==1) H=0;
                H *= 6;
                int sector = floor(H);
                double rl = H-sector;
                double rr = 1.-rl;
                double chroma = V*S;
                switch (sector) {
                        case 0:
                                R = V;
                                G = V-chroma*rr;
                                B = V-chroma;
                                break;
                        case 1:
                                R = V-chroma*rl;
                                G = V;
                                B = V-chroma;
                                break;
                        case 2:
                                R = V-chroma;
                                G = V;
                                B = V-chroma*rr;
                                break;
                        case 3:
                                R = V-chroma;
                                G = V-chroma*rl;
                                B = V;
                                break;
                        case 4:
                                R = V-chroma*rr;
                                G = V-chroma;
                                B = V;
                                break;
                        case 5:
                                R = V;
                                G = V-chroma;
                                B = V-chroma*rl;
                }
                R = fabs(R*255);
                G = fabs(G*255);
                B = fabs(B*255);
        }
        //---------------------------------------------------------------------------
}