R/canvas_cobweb.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 Cobwebs
#'
#' @description This function draws a cobweb on the canvas. The cobweb consists
#' of many Fibonacci spirals shifted by random noise from a normal distribution.
#' A Fibonacci spiral is a logarithmic spiral that is derived from the
#' Fibonacci sequence, a mathematical sequence where each number is the sum of
#' the two preceding ones. The spiral is created by connecting the corners of
#' squares that are sized according to the Fibonacci sequence. Specifically, if
#' we draw a sequence of squares with side lengths of 1, 1, 2, 3, 5, 8, 13, and
#' so on, each square can be arranged so that it is tangent to the previous
#' square at a corner. When we connect these corners with a smooth curve, the
#' resulting shape is the Fibonacci spiral.
#'
#' @usage canvas_cobweb(
#'   colors,
#'   background = "#fafafa",
#'   lines = 300,
#'   iterations = 100
#' )
#'
#' @param colors      a string or character vector specifying the color(s) used for the artwork.
#' @param background  a character specifying the color used for the background.
#' @param lines       the number of lines to draw.
#' @param iterations  the number of iterations of the algorithm.
#'
#' @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_cobweb(colors = colorPalette("neon1"), background = "black")
#' }
#'
#' @export

canvas_cobweb <- function(colors,
                          background = "#fafafa",
                          lines = 300,
                          iterations = 100) {
  .checkUserInput(background = background, iterations = iterations)
  fibonacci <- .cobweb_fibonacci(n = iterations)
  seqn <- seq_len(iterations)
  nrows <- length(seqn - 3) * lines
  canvas <- data.frame(x = rep(NA, nrows), xend = rep(NA, nrows), y = rep(NA, nrows), yend = rep(NA, nrows), z = rep(NA, nrows), lwd = rep(NA, nrows), col = rep(NA, nrows))
  for (i in 1:lines) {
    x1 <- ifelse(seqn %% 2 == 1, yes = fibonacci, no = 0)
    y1 <- ifelse(seqn %% 2 == 0, yes = fibonacci, no = 0)
    x2 <- ifelse(seqn %% 4 == 1, yes = x1, no = -x1)
    y2 <- ifelse(seqn %% 4 == 2, yes = y1, no = -y1)
    suppressWarnings({
      x <- ifelse(x2 > 0, log(x2), ifelse(x2 < 0, -log(-x2), 0)) * stats::rnorm(length(x2))
      y <- ifelse(y2 > 0, log(y2), ifelse(y2 < 0, -log(-y2), 0)) * stats::rnorm(length(x2))
    })
    xend <- c(x[-1], x[1])
    yend <- c(y[-1], y[1])
    subdata <- data.frame(x = x, xend = xend, y = y, yend = yend, z = i, lwd = stats::runif(1, 0, 0.1), col = sample(colors, size = 1))
    subdata <- subdata[-which(subdata[["x"]] == subdata[["xend"]] | subdata[["y"]] == subdata[["yend"]]), ]
    ind <- which(is.na(canvas[["x"]]))[1]
    canvas[ind:(ind + nrow(subdata) - 1), ] <- subdata[stats::complete.cases(subdata), ]
  }
  canvas <- canvas[stats::complete.cases(canvas), ]
  artwork <- ggplot2::ggplot() +
    ggplot2::geom_curve(
      data = canvas, mapping = ggplot2::aes(x = x, y = y, xend = xend, yend = yend, group = z),
      color = canvas[["col"]], curvature = stats::runif(1, 0, 0.8), ncp = 25, linewidth = canvas[["lwd"]], alpha = 0.01
    ) +
    ggplot2::coord_cartesian(
      xlim = c(min(canvas[["x"]]) / 4, max(canvas[["x"]]) / 4),
      ylim = c(min(canvas[["y"]]) / 4, max(canvas[["y"]]) / 4)
    )
  artwork <- theme_canvas(artwork, background = background)
  return(artwork)
}

.cobweb_fibonacci <- function(n) {
  x <- c(0, 1)
  for (i in 3:n) {
    x[i] <- x[i - 1] + x[i - 2]
  }
  x <- x[-1]
  return(x)
}