R/canvas_stripes.R

In aRtsy: Generative Art with 'ggplot2'

# Copyright (C) 2021-2023 Koen Derks

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

#' Draw Stripes
#'
#' @description This function creates a brownian motion on each row of the artwork and colors it according to the height of the motion.
#'
#' @usage canvas_stripes(
#'   colors,
#'   n = 300,
#'   H = 1,
#'   burnin = 1
#' )
#'
#' @param colors      a string or character vector specifying the color(s) used for the artwork.
#' @param n           a positive integer specifying the length of the brownian motion (effectively the width of the artwork).
#' @param H           a positive value specifying the square of the standard deviation of each step in the motion.
#' @param burnin      a positive integer specifying the number of steps to discard before filling each row.
#'
#' @return A \code{ggplot} object containing the artwork.
#'
#' @author Koen Derks, \email{koen-derks@hotmail.com}
#'
#' @keywords artwork canvas
#'
#' @seealso \code{colorPalette}
#'
#' @examples
#' \donttest{
#' set.seed(1)
#'
#' # Simple example
#' canvas_stripes(colors = colorPalette("random", n = 10))
#' }
#'
#' @export

canvas_stripes <- function(colors,
                           n = 300,
                           H = 1,
                           burnin = 1) {
  stopifnot("'burnin' must be a single integer >= 1" = burnin > 0 && burnin %% 1 == 0 && length(burnin) == 1)
  mat <- matrix(NA, nrow = n, ncol = n)
  for (i in seq_len(nrow(mat))) {
    t <- seq_len(n + burnin)
    x <- stats::rnorm(n = length(t) - 1, sd = sqrt(H))
    x <- c(0, cumsum(x))
    mat[i, ] <- rev(x[-(1:burnin)])
  }
  canvas <- .unraster(mat, names = c("x", "y", "z"))
  artwork <- ggplot2::ggplot(data = canvas, ggplot2::aes(x = x, y = y, fill = z)) +
    ggplot2::geom_raster(interpolate = TRUE) +
    ggplot2::scale_fill_gradientn(colours = colors)
  artwork <- theme_canvas(artwork)
  return(artwork)
}