set R color alpha value — alpha2col • jamba

Define the alpha transparency per R color

Usage

alpha2col(x, alpha = 1, maxValue = 1, ...)

Arguments

x: R compatible color, either a color name, or hex value, or a mixture of the two. Any value compatible with col2rgb.
alpha: numeric alpha transparency to use per x color. alpha is recycled to length(x) as needed.
maxValue: numeric maximum value to return, useful when the downstream alpha range should be 255. By default maxValue=1 is returned.
...: Additional arguments are ignored.

Value

character vector of R colors, with alpha values.

See also

Other jam color functions: applyCLrange(), col2alpha(), col2hcl(), col2hsl(), col2hsv(), color2gradient(), fixYellow(), fixYellowHue(), getColorRamp(), hcl2col(), hsl2col(), hsv2col(), isColor(), kable_coloring(), makeColorDarker(), rainbow2(), rgb2col(), setCLranges(), setTextContrastColor(), showColors(), unalpha(), warpRamp()

Examples

withr::with_par(list("mfrow"=c(2,2)), {
for (alpha in c(1, 0.8, 0.5, 0.2)) {
   nullPlot(plotAreaTitle=paste0("alpha=", alpha),
      doMargins=FALSE);
   usrBox(fill=alpha2col("yellow",
      alpha=alpha));
}
})