[R-sig-Geo] semi-transparent layer with image()

hadley wickham h.wickham at gmail.com
Fri Nov 16 23:34:55 CET 2007


There's the alpha function in the ggplot2 package:

plot(1:90, 1:90, pch=16, cex=2, col="red")
points(1:90, 1:90, pch=16, cex=2, col=alpha(grey(90:1/90), 0.5))

Hadley

On 11/16/07, Ingo Holz <Ingo.Holz at uni-hohenheim.de> wrote:
> Hi,
>
>  is there an easier way to get a semi-transparent grey-palette?
>
>  plot(1:90, 1:90, pch=16, cex=2, col="red")
>  points(1:90, 1:90, pch=16, cex=2, col=rgb(t(col2rgb(grey(90:1/90))),
> alpha=100, maxColorValue=255))
>
>  windows() does support semi-transparent colours
>
> Thanks,
> Ingo
>
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>
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