Convert color hex code to color names

Actually all 6 colors in rainbow(6) do have names. I missed the fact that
rainbow() adds an alpha value that we need to strip off before comparing to
the values in clrs$RGB:

rain <- substr(rain, 1, 7)
sum(clrs$RGB %in% rain)

[1] 12

So there are two color names for each color in rainbow(6):

for (i in 1:6) cat(i, colors()[clrs$RGB==rain[i]], "\n")

1 red red1
2 yellow yellow1
3 green green1
4 cyan cyan1
5 blue blue1
6 magenta magenta1

David C

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of David L
Carlson
Sent: Monday, April 13, 2015 12:07 PM
To: Boris Steipe; Alejo C.S.
Cc: r-help at r-project.org
Subject: Re: [R] Convert color hex code to color names

And expanding at a more elementary level. The reason you need to find the
smallest difference is
that all of the possible colors do not have names. There are 256^3 =
16,777,216 possible rgb color designations, but only 657 named colors. You
can create a data frame of the named colors and their rgb designations using

clrs <- data.frame(Color=colors(), RGB=rgb(t(col2rgb(colors())),

    maxColorValue=255), stringsAsFactors=FALSE)

str(clrs)

'data.frame':   657 obs. of  2 variables:
 $ Color: chr  "white" "aliceblue" "antiquewhite" "antiquewhite1" ...
 $ RGB  : chr  "#FFFFFF" "#F0F8FF" "#FAEBD7" "#FFEFDB" ...

head(clrs)

          Color     RGB
1         white #FFFFFF
2     aliceblue #F0F8FF
3  antiquewhite #FAEBD7
4 antiquewhite1 #FFEFDB
5 antiquewhite2 #EEDFCC
6 antiquewhite3 #CDC0B0

So most colors do not have names. In your example, none of the colors in
rainbow(6) have names:

rain <- rainbow(6)
sum(clrs$RGB %in% rain)

[1] 0

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352


-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Boris
Steipe
Sent: Monday, April 13, 2015 11:44 AM
To: Alejo C.S.
Cc: r-help at r-project.org
Subject: Re: [R] Convert color hex code to color names

To add slightly to that:

What you want to do is write a function that returns the named color that
has the smallest difference to your input hex-triplet. But note that color
difference is a large topic. Assuming you want to minimize *perceptual*
differences, you want to calculate your differences in Lab color space. The
function convertColor() has the option to convert hex to Lab. Example:
convertColor(t(col2rgb("thistle")), from="sRGB", to="Lab", scale.in=255)

Within Lab space, you can take the Euclidian distance.

That all said, I can't imagine why one would want to do this in the first
place - color triplets are much more convenient than label strings :-)


B.




On Apr 13, 2015, at 11:45 AM, Thierry Onkelinx <thierry.onkelinx at inbo.be>
wrote:

A combination of rgb(), col2rgb() and colors() can gives hex values for

the

named colors.

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature

and

Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to

say

what the experiment died of. ~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data. ~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of

data.

~ John Tukey

2015-04-13 17:28 GMT+02:00 Alejo C.S. <alej.c.s at gmail.com>:

Hi all, I want to convert the output of:

rainbow(6)

[1] "#FF0000FF" "#FFFF00FF" "#00FF00FF" "#00FFFFFF" "#0000FFFF"

"#FF00FFFF"

To a vector of color names. Any tip?


Thanks in advance

C.

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