colors.prevR.r

#' Continuous color palettes.
#'
#' Functions generating color palettes usable with \R graphical functions.
#' These palettes are continuous, contrast being accentuated by darkening
#' and lightening extreme values. \code{prevR.demo.pal} plot the available
#' palettes. \code{prevR.colors.qgis.pal} export a palette in a text file
#' readable by Quantum GIS, an open-source mapping software.
#'
#' @param n number of different colors in the palette.
#'
#' @details
#'
#' [prevR.colors.red()] produces a color gradation from white/yellow
#' to red/dark red.
#'
#' [prevR.colors.blue()] produces a color gradation from light blue
#' to dark blue.
#'
#' [prevR.colors.green()] produces a color gradation from light green
#' to dark green.
#'
#' [prevR.colors.gray()] produces a color gradation from white/light gray to
#' dark gray/black.
#'
#' Functions with a suffix \emph{.inverse} produce the same color gradation,
#' but from dark colors to light ones.
#'
#' @return
#' [prevR.demo.pal()] plot the color palettes.
#'
#' [prevR.colors.qgis.pal()] export a color palette in a text file readable
#' by Quantum GIS.
#'
#' The other functions return a list of colors coded in hexadecimal.
#'
#' @note
#' To obtain the list of colors in RGB (Red/Green/Blue), use the function
#' [grDevices::col2rgb()].
#' The code of [prevR.demo.pal()] was adapted from the function \code{demo.pal}
#' presented in the examples of [grDevices::rainbow()].
#'
#' @seealso Other color palettes are available in \R. See for example
#' [grDevices::rainbow()] or the package \pkg{RColorBrewer}.
#'
#' @examples
#' prevR.demo.pal(25)
#' prevR.colors.red(5)
#' col2rgb(prevR.colors.red(5))
#'
#' \dontrun{
#' prevR.colors.qgis.pal("palette.txt", seq(0, 25, length.out = 100), "red")
#' }
#'
#' @name prevR.colors
#' @export
#' @keywords color
prevR.colors.blue <-
  function(n = 10) {
    if ((n <- as.integer(n[1])) > 0) {
      j <- n %/% 2.75
      i <- n - 2 * j
      c(if (j > 0) {
        hsv(h = 26 / 48, s = seq(
          to = 1 - 1 / (2 * j),
          from = 1 / (2 * j), length = j
        ), v = 1)
      }, hsv(h = seq(26 / 48,
        33 / 48,
        length = i
      )), if (j > 0) {
        hsv(h = 33 / 48, v = seq(from = 1 -
          1 / (2 * j), to = 1 / (2 * j), length = j), s = 1)
      })
    } else {
      character(0)
    }
  }

#' @export
#' @rdname prevR.colors
prevR.colors.blue.inverse <-
  function(n = 10) {
    if ((n <- as.integer(n[1])) > 0) {
      j <- n %/% 2.75
      i <- n - 2 * j
      c(if (j > 0) {
        hsv(h = 33 / 48, v = seq(
          to = 1 - 1 / (2 * j),
          from = 1 / (2 * j), length = j
        ), s = 1)
      }, hsv(h = seq(33 / 48,
        26 / 48,
        length = i
      )), if (j > 0) {
        hsv(h = 26 / 48, s = seq(from = 1 -
          1 / (2 * j), to = 1 / (2 * j), length = j), v = 1)
      })
    } else {
      character(0)
    }
  }

#' @export
#' @rdname prevR.colors
prevR.colors.gray <-
  function(n = 10) {
    if ((n <- as.integer(n[1])) > 0) {
      i <- n - 1
      gray(i:0 / i)
    } else {
      character(0)
    }
  }

#' @export
#' @rdname prevR.colors
prevR.colors.gray.inverse <-
  function(n = 10) {
    if ((n <- as.integer(n[1])) > 0) {
      i <- n - 1
      gray(0:i / i)
    } else {
      character(0)
    }
  }

#' @export
#' @rdname prevR.colors
prevR.colors.green <-
  function(n = 10) {
    if ((n <- as.integer(n[1])) > 0) {
      j <- n %/% 2
      i <- n - 2 * j
      c(if (j > 0) {
        hsv(h = 1 / 3, s = seq(
          to = 1 - 1 / (2 * j),
          from = 1 / (2 * j), length = j
        ), v = 1)
      }, hsv(h = seq(1 / 3,
        1 / 3,
        length = i
      )), if (j > 0) {
        hsv(h = 1 / 3, v = seq(from = 1 -
          1 / (2 * j), to = 1 / (2 * j), length = j), s = 1)
      })
    } else {
      character(0)
    }
  }

#' @export
#' @rdname prevR.colors
prevR.colors.green.inverse <-
  function(n = 10) {
    if ((n <- as.integer(n[1])) > 0) {
      j <- n %/% 2
      i <- n - 2 * j
      c(if (j > 0) {
        hsv(h = 1 / 3, v = seq(
          to = 1 - 1 / (2 * j),
          from = 1 / (2 * j), length = j
        ), s = 1)
      }, hsv(h = seq(1 / 3,
        1 / 3,
        length = i
      )), if (j > 0) {
        hsv(h = 1 / 3, s = seq(from = 1 -
          1 / (2 * j), to = 1 / (2 * j), length = j), v = 1)
      })
    } else {
      character(0)
    }
  }

#' @export
#' @rdname prevR.colors
prevR.colors.red <-
  function(n = 10) {
    if ((n <- as.integer(n[1])) > 0) {
      j <- n %/% 3.5
      i <- n - 2 * j
      c(if (j > 0) {
        hsv(h = 1 / 6, s = seq(
          to = 1 - 1 / (2 * j),
          from = 1 / (2 * j), length = j
        ), v = 1)
      }, hsv(h = seq(1 / 6,
        0,
        length = i
      )), if (j > 0) {
        hsv(h = 0, v = seq(from = 1 -
          1 / (2 * j), to = 1 / (2 * j), length = j), s = 1)
      })
    } else {
      character(0)
    }
  }

#' @export
#' @rdname prevR.colors
prevR.colors.red.inverse <-
  function(n = 10) {
    if ((n <- as.integer(n[1])) > 0) {
      j <- n %/% 3.5
      i <- n - 2 * j
      c(
        if (j > 0) {
          hsv(h = 0, v = seq(to = 1 - 1 / (2 * j), from = 1 / (2 *
            j), length = j), s = 1)
        }, hsv(h = seq(0, 1 / 6, length = i)),
        if (j > 0) {
          hsv(h = 1 / 6, s = seq(from = 1 - 1 / (2 *
            j), to = 1 / (2 * j), length = j), v = 1)
        }
      )
    } else {
      character(0)
    }
  }

#' @param border border color.
#' @param main title.
#' @export
#' @rdname prevR.colors
prevR.demo.pal <-
  function(n, border = if (n < 32) "light gray" else NA, main = NULL) {
    # Fonction basee sur demo.pal - cf. aide de la fonction rainbow : ?rainbow
    ch.col <- c(
      "prevR.colors.red.inverse(n)", "prevR.colors.blue.inverse(n)",
      "prevR.colors.green.inverse(n)", "prevR.colors.gray.inverse(n)",
      "prevR.colors.red(n)", "prevR.colors.blue(n)",
      "prevR.colors.green(n)", "prevR.colors.gray(n)"
    )
    nt <- length(ch.col)
    i <- 1:n
    j <- n / nt
    d <- j / 6
    dy <- 2 * d
    if (missing(main))
      main <- gettextf("prevR.colors palettes for n=%d", n, domain = "R-prevR")
    plot(i, i + d, type = "n", yaxt = "n", xlab = "n", ylab = "", main = main)
    for (k in 1:nt) {
      rect(
        i - .5, (k - 1) * j + dy, i + .4,
        k * j,
        col = eval(parse(text = ch.col[k])),
        border = border
      )
      text(2 * j, k * j + dy / 4, ch.col[k], cex = 0.8)
    }
  }

# Fonction prevR.colors.qgis.pal()
# Permet de generer une palette de couleurs utilisable par Quantum GIS
# Il s'agit d'un fichier txt
# Les lignes sont de la forme :
# -12.5,0,68,27,255,Color entry 1
# valeur,Rouge,Vert,Bleu,Transparence,Nom couleur
# pal vaut red, green, blue ou gray (selection de la palette)
# inverse : si true, prendre l'ordre inverse
# at : liste des valeurs de la palette
# n : nombre de couleurs
# file : nom du fichier

#' @param file file name with extension.
#' @param at list of values of the palette.
#' @param pal color palette to use ("red", "green", "blue" or "gray").
#' @param inverse use the inverse palette?
#' @export
#' @rdname prevR.colors
prevR.colors.qgis.pal <- function(file, at, pal = "red", inverse = FALSE) {
  n.pal <- paste("prevR.colors.", pal, sep = "")
  if (inverse) {
    n.pal <- paste(n.pal, ".inverse", sep = "")
  }
  f.pal <- get(n.pal)
  write.table(
    format(data.frame(
      at,
      t(col2rgb(f.pal(length(at)))),
      rep(255, length.out = length(at)),
      rep(n.pal, length.out = length(at))
    ), scientific = FALSE, trim = TRUE),
    file,
    sep = ",", dec = ".",
    col.names = FALSE, row.names = FALSE, quote = FALSE
  )
}