Find the R built-in colour that's closest in RGB space to a given colour

closest_colour.R

# Find the R built-in colour that's closest in RGB space to a given colour
# This can be useful if you have a colour in mind you want to use in your R
# code, but would rather use a pretty built-in name rather than a HEX value.
#
# @param target The target RGB colour, given as a length-3 numeric vector
# @param n The number of top hits to return
# @param superset A vector with all possible colour names to choose from
#
# Note that the closest colour in RGB space is not guaranteed to be the
# closest colour visually, but it works in many cases.
#
# @examples
# closest_colour(c(100, 100, 100))   -> "gray39"
# closest_colour(c(0, 230, 0), 3)    -> "green2" "green" "green1"
# closest_colour(c(240, 150, 30))    -> "goldenrod2"
# closest_colour(col2rgb("red"), 3)  -> "red" "red1" "red2"

library(magrittr)
closest_colour <- function(target, n = 1, superset = colours()) {
  target %<>% as.numeric
  
  # Find the manhattan distance from each colour to the target colour
  superset %>%
  col2rgb %>% 
  subtract(target) %>% 
  apply(2, function(x) x %>% abs %>% sum) %>% 
  order %>%   
  .[1:n] %>%
  superset[.]
}

# This version takes HEX colours instead of RGB vectors, and can
# deal with multiple colour inputs.
# @examples
# closest_colour_hex(c("#ff0010", "#f1f1f1"))  ->  c("red", "gray94")
closest_colour_hex <- function(targets, n = 1, superset = colours()) {
  vapply(targets, function(target) {
    target <- target %>% col2rgb %>% as.numeric
    
    # Find the manhattan distance from each colour to the target colour
    superset %>%
      col2rgb %>% 
      subtract(target) %>% 
      apply(2, function(x) x %>% abs %>% sum) %>% 
      order %>%   
      .[1:n] %>%
      superset[.]
  }, character(n))
}

Very useful, thanks!