R/color.R

In FastUtils: Fast, Readable Utility Functions

#' Compute the Average of Hex Colors
#'
#' This function computes the average color of the provided hex color values.
#'
#' @param ... Hex color values as character strings. Could also be any number
#' of character vectors (including lists) which will all be coerced into one
#' character, assuming they are valid hex codes.
#'
#' @return A single hex color character representing the average of the input
#' colors.
#' @export
#' @keywords color
#'
#' @source <https://stackoverflow.com/questions/649454>
#'
#' @examples
#' getAvgHex("#000000", "#FF00FF")
#' getAvgHex(c("#008040", "#000000", "#FF00FF"))
#'
#' # very nonstandard but possible way to input hexes. Essentially,
#' # any combination of vectors will work.
#' getAvgHex(list("#008040", "#000000"), "#FF00FF", c("#FF00FF"))
#'
getAvgHex <- function(...) {

    hexVector <- unlist(list(...))

    Reduce(add, lapply(hexVector, grDevices::col2rgb)) %>%
        divide(length(hexVector)) %>%
        round() %>%
        t() %>%
        grDevices::rgb(maxColorValue = 256)
}

#' Scale the Brightness of a Hex Color
#'
#' This function scales the brightness of hex colors by a given factor.
#'
#' @param hex Hex color values as characters.
#' @param scaleFactor A numeric value to scale the brightness.
#' A value of 1 returns the original color.
#'
#' @return A hex color value with adjusted brightness.
#' @export
#' @keywords color
#' @examples
#' scaleHex("#404040", 2)
#'
scaleHex <- function(hex, scaleFactor) {

    if (all(scaleFactor == 1)) return(hex)

    hsvColor <- hex %>%
        grDevices::col2rgb() %>%
        grDevices::rgb2hsv()

    hsvColor["v", ] <- bound(hsvColor["v", ] * scaleFactor, 0, 1)

    grDevices::hsv(hsvColor["h", ], hsvColor["s", ], hsvColor["v", ])
}