#3 discuss: generating (randomly) RGB-colors

[Anonymous]

Originally created by: aapo.rantalainen (code.google.com)
Originally owned by: aapo.rantalainen (code.google.com)

This is discussion about generating (randomly) RGB-colors, so they are not
all approx [0.5 , 0.5 , 0.5]?

First version:
{{{
void getColors(float *red, float *green, float *blue){
int r=rand ();
int g=rand ();
int b=rand ();

*red=(r+0.0)/RAND_MAX;
*green=(g+0.0)/RAND_MAX;
*blue=(b+0.0)/RAND_MAX;
}
}}}

Second version: (little test-tweaking)
{{{
void getColors(float *red, float *green, float *blue){
int r=rand ();
int g=rand ();
int b=rand ();

*red=(r+0.0)/RAND_MAX;
*green=(g+0.0)/RAND_MAX;
*blue = *red+*green;
if (*blue >1.0)
   *blue=*blue-1.0;
}
}}}

Third version: (this is almost good)
{{{
/*
Because random number generator is NOT initialized, this gives same numbers
each time when program runs.
I try generate three numbers [0,1], that all is not approx 0,5.
First I randomize red and green, and if they are 'too middle' I fix blues
value.

The point is:
red   = random value [0,1]
green = random value [0,1]

There are 4 'slots' which red and green might be.
  0    low     mid=0.5     hig    1
R |     |         |         |     |
G |     |         |         |     |

case 1:
  0    low     mid=0.5     hig    1
R |     |    X    |         |     |
G |     |    X    |         |     |
B |     |         |         |  X  |

case 2:
  0    low     mid=0.5     hig    1
R |     |         |    X    |     |
G |     |         |    X    |     |
B |  X  |         |         |     |

case 3:
  0    low     mid=0.5     hig    1
R |     |         |    X    |     |
G |     |    X    |         |     |
B |  X  |         |         |  X  |

case 4:
  0    low     mid=0.5     hig    1
R |     |    X    |         |     |
G |     |         |    X    |     |
B |  X  |         |         |  X  |

*/
void getColors(float *red, float *green, float *blue){
int r=rand ();
*red=(r+0.0)/RAND_MAX;
int g=rand ();
*green=(g+0.0)/RAND_MAX;

float low = 0.2;
float mid = 0.5;
float hig = 1-low;
if (*red>low && *red<mid && *green>low && *green<mid)
   {
   *blue=(rand()+0.0)/RAND_MAX / (1/low) + hig;
   }
else if (*red>mid && *red<hig && *green>mid && *green<hig)
   {
   *blue=(rand()+0.0)/RAND_MAX / (1/low);
   }
else if (*red>low && *red<hig && *green>low && *green<hig)
   {
   *blue=(rand()+0.0)/RAND_MAX / 2.0;
   int b=rand (); /*toss a coin */
   if (b<RAND_MAX/2)
      *blue=*blue*2 / (1/low);
   else
      *blue=*blue*2 / (1/low) + hig;
   }
else
   {
   int b=rand ();
   *blue=(b+0.0)/RAND_MAX;
   }

//printf("%lf,%lf,%lf\n",*red,*green,*blue);
}
}}}