colorspaces.cpp

#include "colorspaces.hpp"
#include <cmath>
#include <cstdlib>
 
//quick and dirty RGB<->HSV conversion from https://stackoverflow.com/questions/3018313/algorithm-to-convert-rgb-to-hsv-and-hsv-to-rgb-in-range-0-255-for-both
 
hsv rgb2hsv(rgb in)
{
    hsv         out;
    double      min, max, delta;
 
    min = in.r < in.g ? in.r : in.g;
    min = min  < in.b ? min  : in.b;
 
    max = in.r > in.g ? in.r : in.g;
    max = max  > in.b ? max  : in.b;
 
    out.v = max;                                // v
    delta = max - min;
    if (delta < 0.00001)
    {
        out.s = 0;
        out.h = 0; // undefined, maybe nan?
        return out;
    }
    if( max > 0.0 ) { // NOTE: if Max is == 0, this divide would cause a crash
        out.s = (delta / max);                  // s
    } else {
        // if max is 0, then r = g = b = 0
        // s = 0, h is undefined
        out.s = 0.0;
        out.h = NAN;                            // its now undefined
        return out;
    }
    if( in.r >= max )                           // > is bogus, just keeps compilor happy
        out.h = ( in.g - in.b ) / delta;        // between yellow & magenta
    else
    if( in.g >= max )
        out.h = 2.0 + ( in.b - in.r ) / delta;  // between cyan & yellow
    else
        out.h = 4.0 + ( in.r - in.g ) / delta;  // between magenta & cyan
 
    out.h *= 60.0;                              // degrees
 
    if( out.h < 0.0 )
        out.h += 360.0;
 
    return out;
}
 
 
rgb hsv2rgb(hsv in)
{
    double      hh, p, q, t, ff;
    long        i;
    rgb         out;
 
    if(in.s <= 0.0) {       // < is bogus, just shuts up warnings
        out.r = in.v;
        out.g = in.v;
        out.b = in.v;
        return out;
    }
    hh = in.h;
    if(hh >= 360.0) hh = 0.0;
    hh /= 60.0;
    i = (long)hh;
    ff = hh - i;
    p = in.v * (1.0 - in.s);
    q = in.v * (1.0 - (in.s * ff));
    t = in.v * (1.0 - (in.s * (1.0 - ff)));
 
    switch(i) {
    case 0:
        out.r = in.v;
        out.g = t;
        out.b = p;
        break;
    case 1:
        out.r = q;
        out.g = in.v;
        out.b = p;
        break;
    case 2:
        out.r = p;
        out.g = in.v;
        out.b = t;
        break;
 
    case 3:
        out.r = p;
        out.g = q;
        out.b = in.v;
        break;
    case 4:
        out.r = t;
        out.g = p;
        out.b = in.v;
        break;
    case 5:
    default:
        out.r = in.v;
        out.g = p;
        out.b = q;
        break;
    }
    return out;
}
 
rgb fromRGB(int r, int g, int b)
{
    return { r/255.0, g/255.0, b/255.0 };
}
 
double randd() {
  return (double)std::rand() / ((double)RAND_MAX + 1);
}
 
rgb randomColor()
{
    return (rgb){ randd(), randd(), randd() };
}