[rrd-users] Re: CDEFs and graduated colors

[Serge Maandag]

Check out the hsv color model:
http://www.diaginc.com/forum/July_2002/

By changing the hue in the hsv color model you can calculate colors that fluently go from blue to red.

Check out this newsgroup article:

http://groups.google.com/groups?q=rgb+to+hsv+perl&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&selm=nadie3a50e94c12145%40news.latino-2000.com&rnum=1

It features code to convert rgb to hsv and vice versa.
Combine it with your idea and make a routine that returns an array of rgb values to spread over your cdefs.

Serge.


> Been trying to get my head round a little problem with RRD. I've set it up
> to print some pretty flame graphs using CDEFs - basically by making 255
> CDEFs each 1/255th of the data value and stacking them up with a color which
> increments from blue to red.
>
> What I was looking to do was come up with a way to have the color get redder
> ( i.e. hotter ) as the actual value increases. So for example a graph
> showing data ranging from 0 - 25% would be a comforting blueish-purple ,
> while one getting to 70 odd percent would have a blue base with a "flame"
> that gets pretty red at the top of the graph.

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