Add an Alpha Channel To a Color
Add transparency to a color defined by its name or number. The function first converts the color to RGB and then appends the alpha channel.
SetAlpha(col, alpha = 0.5)
- vector of two kind of R colors, i.e., either a color name (an element of
colors()) or an integer i meaning
- the alpha value to be added. This can be any value from 0 (fully transparent) to 1 (opaque).
NAis interpreted so as to delete a potential alpha channel. Default is 0.5.
All arguments are recyled as necessary.
Vector with the same length as
col, giving the rgb-values extended by the alpha channel as hex-number (#rrggbbaa).
SetAlpha("yellow", 0.2) SetAlpha(2, 0.5) # red Canvas(3) DrawCircle(x=c(-1,0,1), y=c(1,-1,1), r.out=2, col=SetAlpha(2:4, 0.4)) x <- rnorm(15000) par(mfrow=c(1,2)) plot(x, type="p", col="blue" ) plot(x, type="p", col=SetAlpha("blue", .2), main="Better insight with alpha channel" )
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