R/convert_color.R

In jfjelstul/eumaps: Tools to make maps of the European Union

# Joshua C. Fjelstul, Ph.D.
# eumaps R package

#' Convert colors
#'
#' This function converts colors to an 8-digit hex format (e.g., `#FFFFFFFF`). It supports
#' RGB values, with or without an alpha value, and with a maximum of 1 or 255. It also
#' supports hex values, with or without an alpha value, and without or without a leading `#`.
#'
#' @return This function returns a color in an 8-digit hex format with a leading `#` (e.g., `#FFFFFFFF`).
#'
#' @param color Color. Required, and does not have a default value. This argument can be an RGB color
#' specified as a vector with 3 or 4 values, as in c(1, 1, 1), c(1, 1, 1, 1), c(255, 255, 255), or c(255, 255, 255, 255), or
#' a hex color specified as a string, as in `#FFFFFF`, `#FFFFFFFF`, `FFFFFF`, or `FFFFFFFF`.
#'
#' @examples
#' convert_color(c(1, 1, 1)) # RGB, no alpha, max 1
#' convert_color(c(1, 1, 1, 1)) # RGB, alpha, max 1
#' convert_color(c(255, 255, 255)) # RGB, no alpha, max 255
#' convert_color(c(255, 255, 255, 255)) # RGB, alpha, max 255
#' convert_color("#FFFFFF") # hex, no alpha, with #
#' convert_color("#FFFFFFFF") # hex, alpha, with #
#' convert_color("FFFFFF") # hex, no alpha, without #
#' convert_color("FFFFFFFF") # hex, alpha, without #
#'
#' @export
convert_color <- function(color) {

  # if RGB
  if(length(color) == 3 | length(color) == 4) {

    # if no alpha
    if(length(color) == 3) {

      # if max value is 1
      if(color[1] <= 1 & color[2] <= 1 & color[3] <= 1) {
        color <- rgb(color[1], color[2], color[3], 1, maxColorValue = 1)
      }

      # if max value is 255
      else {
        color <- rgb(color[1], color[2], color[3], 255, maxColorValue = 255)
      }
    }

    # if alpha
    else {

      # if max value is 1
      if(color[1] <= 1 & color[2] <= 1 & color[3] <= 1 & color[4] <= 1) {
        color <- rgb(color[1], color[2], color[3], color[4], maxColorValue = 1)
      }

      # if max value is 255
      else {
        color <- rgb(color[1], color[2], color[3], color[4], maxColorValue = 255)
      }
    }
  }

  # if hex
  else if(length(color) == 1){

    if(!stringr::str_detect(color, "^(#)?([A-Z0-9]{6}|[A-Z0-9]{8})$")) {
      stop("please enter a valid RGB or HEX color")
    }

    # if 6 digits, convert to 8 digits
    if(stringr::str_detect(color, "^(#)?[A-Z0-9]{6}$")) {
      color <- stringr::str_c(color, "FF")
    }

    # add a # if needed
    if(!stringr::str_detect(color, "^#")) {
      color <- stringr::str_c("#", color)
    }
  }

  else {
    stop("The argument 'color' should be an RGB color as a numeric vector (of length 3 or 4) or a hex color as a string.")
  }

  return(color)
}