Dear Thomas,
This seems simpler than the solution that I used, so I'll give it a
try.
Thanks,
John
On Tue, 22 May 2007 09:01:01 -0700 (PDT)
Thomas Lumley <[EMAIL PROTECTED]> wrote:
> On Mon, 21 May 2007, John Fox wrote:
> >
> > In retrospect, I didn't specify the problem clearly: What I want to
> be able
> > to do is to place text on a background of arbitrary (but known RGB)
> colour
> > so that the text is legible. I guess that this is better described
> as a
> > "contrasting" than a "complementary" colour.
>
> Since luminance contrasts are necessary and sufficient for readable
> text, you could use white for dark colors and black for light colors.
>
> Luminance is roughly proportional to 0.2*(R^2.4)+0.6*(G^2.4),
> suggesting something like
>
> lightdark<-function (color)
> {
> rgb <- col2rgb(color)/255
> L <- c(0.2, 0.6, 0) %*% rgb
> ifelse(L >= 0.2, "#000060", "#FFFFA0")
> }
>
> This uses a pale yellow for dark backgrounds and a dark blue for
> light backgrounds, and it seems to work reasonably well.
>
> -thomas
--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
http://socserv.mcmaster.ca/jfox/
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