R/plot_tiles.R

In maptiles: Download and Display Map Tiles

#' @title Plot map tiles
#' @description Plot map tiles.
#' @name plot_tiles
#' @param x a SpatRaster object.
#' @param add whether to add the layer to an existing plot (TRUE) or
#' not (FALSE).
#' @param ... bgalpha, smooth, or other arguments passed to be passed to
#' \code{\link[terra:plotRGB]{plotRGB}}
#' @param adjust if TRUE, plot the raster without zoom-in or zoom-out in the
#' graphic device: add margins if the raster is smaller than the graphic device,
#' zoom-in if the raster is larger than the graphic device. This feature does
#' not work with an unprojected (lon/lat) raster.
#' @note This function is a wrapper for \code{\link[terra:plotRGB]{plotRGB}}
#' from the terra package.
#' @export
#' @importFrom graphics plot.new plot.window
#' @importFrom grDevices dev.size
#' @examples
#' \dontrun{
#' library(sf)
#' library(maptiles)
#' nc <- st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
#' nc_osm <- get_tiles(nc, crop = TRUE)
#' plot_tiles(nc_osm)
#' }
plot_tiles <- function(x, adjust = FALSE, add = FALSE, ...) {
  if (!inherits(x, "SpatRaster")) {
    stop(paste0("x should be a SpatRaster"), call. = FALSE)
  }
  ops <- list(...)
  ops$x <- x
  ops$add <- add
  # Default opts
  ops$maxcell <- ifelse(is.null(ops$maxcell), Inf, ops$maxcell)
  ops$bgalpha <- ifelse(is.null(ops$bgalpha), 0, ops$bgalpha)
  ops$smooth <- ifelse(is.null(ops$smooth), TRUE, ops$smooth)


  # Add margins if the raster is smaller than the device
  # Zoom-in if the raster is larger than the device
  if (adjust == TRUE && add == FALSE) {
    if (terra::is.lonlat(ops$x)) {
      message(paste0("The 'adjust' feature does not work with",
                     " an unprojected (lon/lat) raster."))
    } else {
      tsp <- dim(ops$x)[2:1]
      dsp <- dev.size("px")
      dsi <- dev.size("in")
      dd <- ((dsp - tsp) / 2) / (dsp / dsi)
      dd <- c(dd[2:1], dd[2:1]) / 0.2
      if (min(dd) >= 0) {
        ops$mar <- dd
      } else {
        et <- terra::ext(ops$x)
        rt <- terra::res(ops$x)[1]
        wp <- (tsp[1] - dsp[1]) / 2
        hp <- (tsp[2] - dsp[2]) / 2
        et[1:4] <- c(et[1] + wp * rt, et[2] - wp * rt,
                     et[3] + hp * rt, et[4] - hp * rt)
        ops$ext <- et
      }
      ops$smooth <- FALSE
    }
  }
  do.call(terra::plotRGB, ops)
}