How could I find a color that complements another programmatically?

Given any (user selectable) color, I am trying to generate a matching color to go with it for a user interface.

Basically, it should be a color that is either similar, or complements it very well - but, it must also be easily distinguishable from the first color. So far, I have tried lightening/darkening the color, which works ok - but it doesn't look the best, I am not convinced that there is no better way to do it.

What are some alternative or better ways that I could achieve the desired effect? Any help is much appreciated!

-

Side note - 开发者_StackOverflow中文版I have the color in both RGB and HSL formats, although could easily convert to others if need be.

---

Would it be possible for you to use this site below to help you reverse engineer the concept you are looking for?

http://colorschemedesigner.com/

It's flash so you can't see the code, it still might help though.

---

If you can figure out how to produce a colour wheel, then complementary colours are on opposite sides of the wheel.

Update

Wikipedia has useful pages on hue, hsl and hsv

http://en.wikipedia.org/wiki/Hue

http://en.wikipedia.org/wiki/HSL_and_HSV

and more on conversions

http://130.113.54.154/~monger/hsl-rgb.html