R/divide.R

In nrennie/aRt: Generative Art with R

#' Divide
#'
#' This function generates a coloured generative art ggplot object from intersecting lines.
#'
#' @param num_lines Number of intersecting lines. Default `30`.
#' @param col_palette Vector of colours. Default `PrettyCols::prettycols("TangerineBlues")`.
#' @param rayshade Boolean determining whether the returned plot should be converted to
#' three dimensional using rayshader. If `TRUE`, `{rayshader}` is required to be installed.
#' Default `FALSE`.
#' @param s Seed value. Default `1234`.
#' @return A ggplot object.
#' @examples
#' divide()
#' @export

divide <- function(num_lines = 30,
                   col_palette = PrettyCols::prettycols("TangerineBlues"),
                   rayshade = FALSE,
                   s = 1234) {
  num_lines <- ceiling(num_lines)
  if (num_lines < 3) {
    stop("num_lines must be at least 3")
  }
  cropped_sf <- withr::with_seed(
    seed = s,
    code = {
      polygon1 <- sf::st_polygon(list(cbind(c(0, 1, 1, 0, 0), c(0, 0, 1, 1, 0))))
      endpoints <- tibble::tibble(
        x = c(
          seq(0, 1, length = 100),
          seq(0, 1, length = 100),
          rep(0, 100),
          rep(1, 100)
        ),
        y = c(
          rep(0, 100),
          rep(1, 100),
          seq(0, 1, length = 100),
          seq(0, 1, length = 100)
        )
      )
      choose_ends <- purrr::map(
        .x = 1:num_lines,
        .f = ~ as.matrix(dplyr::slice_sample(endpoints, n = 2))
      )
      make_lines <- sf::st_multilinestring(x = choose_ends)
      cropped_sf <- lwgeom::st_split(polygon1, make_lines) |>
        sf::st_collection_extract(c("POLYGON")) |>
        sf::st_as_sf()
      cropped_sf$col <- sample(seq_len(length(col_palette)),
        size = nrow(cropped_sf),
        replace = TRUE
      )
      cropped_sf
    }
  )

  g <- ggplot2::ggplot() +
    ggplot2::geom_sf(
      data = cropped_sf,
      mapping = ggplot2::aes(fill = col),
      colour = NA
    ) +
    ggplot2::scale_fill_gradientn(colours = col_palette) +
    ggplot2::coord_sf(expand = FALSE) +
    theme_aRt(col_palette[1])
  if (rayshade) {
    if (!requireNamespace("rayshader", quietly = TRUE)) {
      stop("Please install {rayshader} to use this argument, or set 'rayshade = FALSE'")
    } else {
      rayshader::plot_gg(g,
        fov = 0,
        theta = 0,
        phi = 90,
        preview = TRUE
      )
    }
  } else {
    return(g)
  }
}