Converts an R color to RGB (red/green/blue) including a transparency (alpha channel).

Converts an R color to RGB (red/green/blue) including a transparency (alpha channel). Similar to col2rgb except that a transparency (alpha channel) can be included.

col2rgbt(col, transp = 1)

Arguments

col	A vector of any of the three kinds of R color specifications (i.e., either a color name (as listed by colors()), a hexadecimal string of the form "#rrggbb" or "#rrggbbaa" (see rgb), or a positive integer i meaning palette()[i].
transp	A numeric vector that indicates the transparency level for the color. The transparency values must be greater than 0. Transparency values greater than 1 are interpreted as the number of points plotted on top of each other before the transparency is lost and is, thus, transformed to the inverse of the transparency value provided.

Value

A vector of hexadecimal strings of the form "#rrggbbaa" as would be returned by rgb.

See also

See col2rgb for similar functionality.

Author

Derek H. Ogle, derek@derekogle.com

Examples

col2rgbt("black")
#> [1] "#000000FF"
col2rgbt("black",1/4)
#> [1] "#00000040"
clrs <- c("black","blue","red","green")
col2rgbt(clrs)
#> [1] "#000000FF" "#0000FFFF" "#FF0000FF" "#00FF00FF"
col2rgbt(clrs,1/4)
#> [1] "#00000040" "#0000FF40" "#FF000040" "#00FF0040"
trans <- (1:4)/5
col2rgbt(clrs,trans)
#> [1] "#00000033" "#0000FF66" "#FF000099" "#00FF00CC"