the number of gray colors (\(\ge 1\)) to be in the
starting gray level in the palette (should be between
0 and 1 where zero indicates "black" and one
ending gray level in the palette.
the gamma correction.
the opacity, is specified.
logical indicating whether the ordering of the colors should
A vector of n gray colors.
The function gray.colors chooses a series of n
gamma-corrected gray levels between start and end:
seq(start^gamma, end^gamma, length = n)^(1/gamma).
The returned palette contains the corresponding gray colors.
This palette is used in barplot.default.