R/gdaldem.R

In gdalUtilities: Wrappers for 'GDAL' Utilities Executables

##' This function provides an interface mirroring that of the GDAL
##' command-line app \code{gdaldem}. For a description of the
##' utility and the arguments that it takes, see the documentation at
##' \url{https://gdal.org/programs/gdaldem.html}.
##'
##' @title Interface to GDAL's gdaldem utility
##' @param input_dem Path to a GDAL-supported readable DEM datasource.
##' @param output_map Character. Path to a GDAL-supported output file.
##' @param mode Character, one of \code{"hillshade"}, \code{"slope"},
##'     \code{"color-relief"}, \code{"TRI"}, \code{"TPI"},
##'     \code{"roughness"}, indicating which of the available
##'     processing modes is to be used.
##' @param ... Here, a placeholder argument that forces users to
##'     supply exact names of all subsequent formal arguments.
##' @param of,compute_edges,alg,b,co,q,z,s,az,alt,combined See the
##'     GDAL project's
##'     \href{https://gdal.org/programs/gdaldem.html}{gdaldem
##'     documentation} for details.
##' @param multidirectional,igor,p,trigonometric,zero_for_flat See the
##'     GDAL project's
##'     \href{https://gdal.org/programs/gdaldem.html}{gdaldem
##'     documentation} for details.
##' @param color_text_file,alpha,exact_color_entry,nearest_color_entry
##'     See the GDAL project's
##'     \href{https://gdal.org/programs/gdaldem.html}{gdaldem
##'     documentation} for details.
##' @param dryrun Logical (default \code{FALSE}). If \code{TRUE},
##'     instead of executing the requested call to GDAL, the function
##'     will print the command-line call that would produce the
##'     equivalent output.
##' @param config_options A named character vector with GDAL config
##'     options, of the form \code{c(option1=value1, option2=value2)}. (See
##'     \href{https://gdal.org/user/configoptions.html}{here} for a
##'     complete list of supported config options.)
##' @return Silently returns path to \code{output_map}.
##' @export
##' @author Joshua O'Brien
##' @examples
##' \donttest{
##' ## Prepare file paths
##' td <- tempdir()
##' in_dem <- system.file("extdata/maunga.tif", package = "gdalUtilities")
##' out_slope  <- file.path(td, "slope.tif")
##' out_shade  <- file.path(td, "shade.tif")
##' out_aspect <- file.path(td, "aspect.tif")
##'
##' ## Apply DEM processing
##' gdaldem("slope", in_dem, out_slope)
##' gdaldem("shade", in_dem, out_shade)
##' gdaldem("aspect", in_dem, out_aspect)
##'
##' ## View results
##' if(require(terra)) {
##'     op <- par(mfcol = c(1, 2))
##'     plot(rast(in_dem),     main = "elevation")
##'     plot(rast(out_slope),  main = "slope")
##'     plot(rast(out_shade),  main = "hillshade")
##'     plot(rast(out_aspect), main = "aspect")
##'     par(op) ## Reset parameters to preexisting values
##' }
##' }
gdaldem <-
    function(mode, input_dem, output_map, ..., of,
             compute_edges, alg, b, co, q, z, s, az, alt, combined,
             multidirectional, igor, p, trigonometric, zero_for_flat,
             color_text_file = character(0), alpha, exact_color_entry,
             nearest_color_entry,
             config_options = character(0), dryrun = FALSE)
{
    ## Unlike `as.list(match.call())`, forces eval of arguments
    args <-  mget(names(match.call())[-1])
    args[c("mode", "input_dem", "output_map", "color_text_file",
           "config_options", "dryrun")] <- NULL
    formalsTable <- getFormalsTable("gdaldem")
    opts <- process_args(args, formalsTable)

    if(dryrun) {
        x <- CLI_call("gdaldem", mode,
                      input_dem, color_text_file, output_map,
                      opts=opts)
        return(x)
    }

    ## (My name for "mode" and "output_map")
    gdal_utils("demprocessing",
               source = input_dem,
               destination = output_map,
               options = opts,
               processing = mode,
               colorfilename = color_text_file,
               config_options = config_options)
    invisible(output_map)
}