[R] detect brightness of hex color value in R / convert from hex to hsl/hsv space how?

[Michael Friendly]

Perhaps some variation of

   SetTextContrastColor <- function(color)
   {
     ifelse( mean(col2rgb(color)) > 127, "black", "white")
   }

Mark Heckmann wrote:
> To the R color experts:
> I need to detect if a chosen background color (as hex e.g. #910322) is  
> light or dark.
> If it is dark I need to ovelay it with light text and vice versa.
> 
> Thus I would like to implement the following pseudo code:
> 
> if (brightness(color) > somevalue) textcolor= dark else textcolor=red
> 
> I am not too familiar with color systems. My idea was to convert the  
> hex value to hsv / hsl space and extract the v or l value.
> 1) I am not sure if this is the way to go.
> 2) I do not succeed in it. convertColor {grDevices} or make.rgb  
> {grDevices} did not help me with that. How can I convert hex to hsv/ 
> hsl space
> 
> How would you detect the (perceived) color brightness?
> 
> Thanks
> Mark
> 
> –––––––––––––––––––––––––––––––––––––––
> Mark Heckmann
> Dipl. Wirt.-Ing. cand. Psych.
> Vorstraße 93 B01
> 28359 Bremen
> Blog: www.markheckmann.de
> R-Blog: http://ryouready.wordpress.com
> 
> 
> 
> 
> 
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> 
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Michael Friendly     Email: friendly AT yorku DOT ca
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