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This function combines any number of images into a single file, which may then be further processed as an image or transformed into an image overlay.


  output_file = tempfile(fileext = ".png"),
  transparency = 0



File paths for images to be combined. Note that combining TIFF images requires the tiff package be installed.


The path to save the resulting image to. Can be any format accepted by magick::image_read. Optionally, can be set to NULL, in which case this function will return the image as a magick object instead of writing to disk.


A value indicating how much transparency should be added to each image. If less than 1, interpreted as a proportion (so a value of 0.1 results in each image becoming 10% more transparent); if between 1 and 100, interpreted as a percentage (so a value of 10 results in each image becoming 10% more transparent.) A value of 0 is equivalent to no additional transparency.


If output_file is not null, output_file, invisibly. If output_file is null, a magick image object.

See also

Other data manipulation functions: georeference_overlay(), merge_rasters(), raster_to_raw_tiles(), vector_to_overlay()

Other overlay creation functions: georeference_overlay(), vector_to_overlay()

Other visualization functions: geom_spatial_rgb(), raster_to_raw_tiles(), vector_to_overlay()


if (FALSE) {
# Generate points and download orthoimagery
mt_elbert_points <- data.frame(
  lat = runif(100, min = 39.11144, max = 39.12416),
  lng = runif(100, min = -106.4534, max = -106.437)

mt_elbert_sf <- sf::st_as_sf(mt_elbert_points, coords = c("lng", "lat"))
sf::st_crs(mt_elbert_sf) <- sf::st_crs(4326)

output_files <- get_tiles(
  output_prefix = tempfile(),
  services = c("ortho")

# Merge orthoimagery into a single file
ortho_merged <- merge_rasters(
  input_rasters = output_files[1],
  output_raster = tempfile(fileext = ".tif")

# Convert our points into an overlay
mt_elbert_overlay <- vector_to_overlay(mt_elbert_sf,
  size = 15,
  color = "red",
  na.rm = TRUE

# Combine the overlay with our orthoimage
ortho_with_points <- combine_overlays(