Color Ramps on Perceptually Linear Scales

Functions for returning colors on perceptually linear scales, where steps correspond to ‘just detectable differences’.

LinGray (n, beg=1, end=92)
BTC     (n, beg=1, end=256)
LinOCS  (n, beg=1, end=256)
heat.ob (n, beg=1, end=256)
magent  (n, beg=1, end=256)
plinrain(n, beg=1, end=256)

Arguments

n

number of colors to return from the ramp

beg

begining of ramp, integer from 1-255

end

end of ramp, integer from 1-255

Value

returns an array of colors

Details

Several precalulated color ramps, that are on a perceptually linear color scale. A perceptually linear color scale is a scale where each jump corresponds to a “just detectable difference” in color and the scale is percieved as linear by the human eye (emprically determined).

When using the ramps, if beg is less than end the ramp will be reversed.

References

Haim Levkowitz (1997) Color Theory and Modeling for Computer Graphics, Visualization, and Multimedia Applications. Kluwer Academic Publishers, Boston/London/Dordrecht. http://www.cs.uml.edu/~haim/ColorCenter/

See also

rainbow, terrain.colors, rgb, hsv

Author

Nicholas Lewin-Koh

Examples

h <- hexbin(rnorm(10000),rnorm(10000))
plot(h, colramp= BTY)

## looks better if you shave the tails:
plot(h, colramp= function(n){LinOCS(n,beg=15,end=225)})