[R] How to use alpha transparency channel for colors?
deepayan at stat.wisc.edu
Thu Oct 7 17:52:33 CEST 2004
On Thursday 07 October 2004 10:01, kwright at eskimo.com wrote:
> The release notes for R 2.0.0 states:
> It is now possible to specify colours with a full alpha
> transparency channel via the new 'alpha' argument to the
> rgb() and hsv() functions, or as a string of the form "#RRGGBBAA".
> NOTE: most devices draw nothing if a colour is not opaque,
> but PDF and Quartz devices will render semitransparent colours.
> A new argument 'alpha' to the function col2rgb()
> provides the ability to return the alpha component of
> colours (as well as the red, green, and blue components).
> I'm using R 2.0.0 on Windows 2000 and wanted to try this feature.
> The following simple test works fine:
You probably just need (see ?pdf)
pdf("c:/alpha.pdf", version = "1.4")
> But as soon as I change alpha value from "ff" to "fe", the points are
> no longer visible for me. I've tried viewing the pdf with Acrobat
> Reader 5.1.0 and gsview4.5.
> Do I need a more recent pdf viewer? Is this feature not working on
> Windows? Am I doing something wrong? Any tips would be appreciated.
> Kevin Wright
More information about the R-help