Add a GeoTIFF file to a leaflet map using optimised rendering.

Usage

addGeotiff(
  map,
  file = NULL,
  url = NULL,
  group = NULL,
  layerId = NULL,
  resolution = 96,
  bands = NULL,
  arith = NULL,
  project = TRUE,
  method = NULL,
  opacity = 0.8,
  options = leaflet::tileOptions(),
  colorOptions = NULL,
  rgb = FALSE,
  pixelValuesToColorFn = NULL,
  autozoom = TRUE,
  ...
)

Arguments

map: the map to add the raster data to.
file: path to the GeoTIFF file to render.
url: url to the GeoTIFF file to render. Ignored if file is provided.
group: he name of the group this raster image should belong to.
layerId: the layerId.
resolution: the target resolution for the simple nearest neighbor interpolation. Larger values will result in more detailed rendering, but may impact performance. Default is 96 (pixels).
bands: which bands to use in case of multi-band Geotiff.
arith: an optional function to be applied to a multi-layer object. Will be computed on-the-fly in the browser.
project: if TRUE (default), automatically project x to the map projection expected by georaster-layer-for-leaflet (EPSG:4326); if FALSE, it's the caller's responsibility to ensure that file is already projected.
method: character defining the resampling method to be used when project is TRUE. See https://gdal.org/programs/gdalwarp.html#cmdoption-gdalwarp-r for possible values.
opacity: opacity of the rendered layer.
options: options to be passed to the layer. See tileOptions for details.
colorOptions: list defining the palette, breaks and na.color to be used.
rgb: logical, whether to render Geotiff as RGB.
pixelValuesToColorFn: optional JS function to be passed to the browser. Can be used to fine tune and manipulate the color mapping. See examples & https://github.com/r-spatial/leafem/issues/25 for some examples.
autozoom: whether to automatically zoom to the full extent of the layer. Default is TRUE
...: currently not used.

Value

A leaflet map object.

Details

This uses the leaflet plugin 'georaster-layer-for-leaflet' to render GeoTIFF data. See https://github.com/GeoTIFF/georaster-layer-for-leaflet for details. The GeoTIFF file is read directly in the browser using geotiffjs (https://geotiffjs.github.io/), so there's no need to read data into the current R session. GeoTIFF files can be read from the file system or via url. The clue is that rendering uses simple nearest neighbor interpolation on-the-fly to ensure smooth rendering. This enables handling of larger rasters than with the standard addRasterImage.

Examples

if (interactive()) {
  library(leaflet)
  library(leafem)
  library(stars)

  tif = system.file("tif/L7_ETMs.tif", package = "stars")
  x1 = read_stars(tif)
  x1 = x1[, , , 3] # band 3

  tmpfl = tempfile(fileext = ".tif")

  write_stars(st_warp(x1, crs = 4326), tmpfl)

  leaflet() %>%
    addTiles() %>%
    addGeotiff(
      file = tmpfl
      , opacity = 0.9
      , colorOptions = colorOptions(
        palette = hcl.colors(256, palette = "inferno")
        , na.color = "transparent"
      )
    )

}