On Fri, 29 Jan 2010, 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.
You can use the "colorspace" package for that. hex2RGB() converts a hex
string to "RGB" coordinates which in turn can be easily converted to
systems like "HSV" or (preferably) HCL (called "polarLUV" in colorspace).
R> as(hex2RGB("#910322"), "polarLUV")
L C H
[1,] 31.61831 95.14145 6.913428
"L" corresponds to the luminance (whether a color is light or dark), "C"
is chroma (how colorful the color is compared to a gray with the same
luminance), and "H" is the hue.
hth,
Z
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
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Mark Heckmann
Dipl. Wirt.-Ing. cand. Psych.
Vorstra?e 93 B01
28359 Bremen
Blog: www.markheckmann.de
R-Blog: http://ryouready.wordpress.com
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