Convert hex color code to color name

Question

How can I translate a hex representation of a color to its corresponding name?

For example, consider the following colors:

rainbow(4)
# "#FF0000FF" "#80FF00FF" "#00FFFFFF" "#8000FFFF"

What are their names (hoping a name exist for each code)?

I discovered the function col2rgb() but it does not exaclty what I am needing.

Answer 1

You may use the convenience function color.id from the plotrix package*:

Given a color specified as a hex string, find the closest match in the table of known (named) colors.

library(plotrix)
sapply(rainbow(4), color.id)
# $`#FF0000FF`
# [1] "red"  "red1"
# 
# $`#80FF00FF`
# [1] "chartreuse"  "chartreuse1"
# 
# $`#00FFFFFF`
# [1] "cyan"  "cyan1"
# 
# $`#8000FFFF`
# [1] "purple"

---

*Credits to Jim Lemon and his answer here: Convert color hex code to color names.

Answer 2

Perhaps not the most elegant solution, but it should get the job done:

color.names <- function(d) {
  # get RGB components of d and convert to data frame
  z2 <- as.data.frame(t(col2rgb(d)))

  # get RGB components of standard colors and convert them to data frame
  z <- as.data.frame(t(sapply(colors(distinct=T),col2rgb)))
  colnames(z) <- colnames(z2)
  z$name <- rownames(z)

  # EDIT: original answer used 'merge', which messed up the order
  library(dplyr)
  z2 %>% left_join(z) %>% select(name) 

}

color.names(rainbow(4))
#   name
# 1  red
# 2 <NA>
# 3 cyan
# 4 <NA>

The function color.names uses the same input as col2rgb, i.e.

vector of any of the three kinds of R color specifications, i.e., either a color name (as listed by colors()), a hexadecimal string of the form "#rrggbb" or "#rrggbbaa" (see rgb), or a positive integer i meaning palette()[i].

so you can use it to get the names of standard colors by doing color.names(1:8)

For computational efficiency, data set with standard colors can be precalculated as in this example:

init.color.names <- function() {
  z <- as.data.frame(t(sapply(colors(distinct=T),col2rgb)))
  colnames(z) <- colnames(z2)
  z$name <- rownames(z)
  library(dplyr)

  function(d) {
    z2 <- as.data.frame(t(col2rgb(d)))     
    z2 %>% left_join(z) %>% select(name)   }
}
cl <- init.color.names()
cl(1:3)
cl(rainbow(4))