A palette that varies the hue of the colors along a scale.

Colors in a rainbow palette all have the same saturation, value and alpha components, while the hue is varied between two given extremes linearly. This palette has the advantage that it wraps around nicely if the hue is varied between zero and one (which is the default).

Example:

>>> pal = RainbowPalette(n=120)
>>> pal.get(0)
(1.0, 0.0, 0.0, 1.0)
>>> pal.get(20)
(1.0, 1.0, 0.0, 1.0)
>>> pal.get(40)
(0.0, 1.0, 0.0, 1.0)
>>> pal = RainbowPalette(n=120, s=1, v=0.5, alpha=0.75)
>>> pal.get(60)
(0.0, 0.5, 0.5, 0.75)
>>> pal.get(80)
(0.0, 0.0, 0.5, 0.75)
>>> pal.get(100)
(0.5, 0.0, 0.5, 0.75)
>>> pal = RainbowPalette(n=120)
>>> pal2 = RainbowPalette(n=120, start=0.5, end=0.5)
>>> pal.get(60) == pal2.get(0)
True
>>> pal.get(90) == pal2.get(30)
True

This palette was modeled after the rainbow command of R.