[R] How to use alpha transparency channel for colors?
kwright at eskimo.com
Thu Oct 7 17:01:16 CEST 2004
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:
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.
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