# [rrd-users] Re: rrdtool- question on line colors

Tobias Oetiker oetiker at ee.ethz.ch
Mon Apr 29 16:02:09 MEST 2002

```Today 'Donald Mahler' wrote:

>
I quite like walking the hsv weal ... here is some code ...

/* code stolen from the gimp */
unsigned int
hsv2rgb(double h, double s, double v, art_u8 alpha)
{
int    j;
double rd, gd, bd;
double f, p, q, t;
if (s == 0.0)
s = 0.000001;
if (h == -1.0) {
rd = v;
gd = v;
bd = v;
} else {
while (h >= 360.0) h = h - 360.0;
while (h <  0.0) h = h + 360.0;
h= h / 60.0;

j = (int)h;
f = h - j;
p = v * (1.0 - s );
q = v * (1.0 - (s*f));
t = v * (1.0 - (s* (1.0 - f)));

switch (j) {
case 0:  rd = v;  gd = t;  bd = p;  break;
case 1:  rd = q;  gd = v;  bd = p;  break;
case 2:  rd = p;  gd = v;  bd = t;  break;
case 3:  rd = p;  gd = q;  bd = v;  break;
case 4:  rd = t;  gd = p;  bd = v;  break;
case 5:  rd = v;  gd = p;  bd = q;  break;
default: rd = v;  gd = t;  bd = p;  break;
}
}
return
((unsigned int)(rd*255.0) << 24) +
((unsigned int)(gd*255.0) << 16) +
((unsigned int)(bd*255.0) << 8) + alpha;
}

>
>
> Does anyone have a mathematical methodology for setting the rrdtool line
> colors that they could share?
>
> I am graphing up to 10 lines on a single graph and there are times that the
> colors are just too close (at least for my... ahem... perception of color :
> -)
>
>
> I was thinking   cycling thru the colors as such...
>
> 000000
> 000033
> 000066
> 000099
> 0000cc
> 330000
> 330033
> 330066
> 3300cc
> 660000
> 660033
> 660066
> 6600cc
>
>
> is this reasonable?   how are others doing this?
>
>
>
> Don M
>
>
>
>
>
> --
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>
>

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