combine_overlays function

Combine multiple image overlays into a single file

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.

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

Arguments

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

• output_file: 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.

• transparency: 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.

Returns

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

Examples

## Not run:

# 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(
  mt_elbert_sf,
  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,
  ortho_merged[[1]],
  size = 15,
  color = "red",
  na.rm = TRUE
)

# Combine the overlay with our orthoimage
ortho_with_points <- combine_overlays(
  ortho_merged[[1]],
  mt_elbert_overlay
)
## End(Not run)

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()