R/animate.R

In angusmoore/arphit: RBA-style R Plots

#' Make slides in gif
#'
#' Flick through arphitgg objects in a gif
#'
#' @param gg_list List of gg objects
#' @param filename Path to save .gif to. If omitted, .gif will be opened
#' externally
#' @param delay Delay in seconds for each frame
#' @param loop Whether to loop through frames. Setting to zero will loop
#' infinitely (default).
#'
#' @return filename if provided, or NULL if not
#' @export
agg_slides <- function(gg_list, filename = NULL, delay = 1, loop = 0) {

  img_list <- lapply(
    seq_along(gg_list),
    function(idx, gg_list) {
      file_name <- file.path(tempdir(), paste0("animate-", idx, ".png"))
      agg_draw(gg_list[[idx]], file_name)
      list(path = file_name, img = magick::image_read(file_name))
    },
    gg_list
  )

  on.exit(unlink(sapply(img_list, "[[", "path")))

  animation <- magick::image_animate(
    image = do.call(c, lapply(img_list, "[[", "img")),
    fps = 1 / delay,
    loop = loop
  )

  if (is.null(filename)) {
    magick::image_browse(animation, browser = NULL)
  } else {
    magick::image_write(animation, path = filename)
  }
}