addGeotiff: Add a GeoTIFF file to a leaflet map using optimised...

In leafem: 'leaflet' Extensions for 'mapview'

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

Description

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.

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.

Value

A leaflet map object.

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"
      )
    )

}

leafem documentation built on Sept. 18, 2023, 1:06 a.m.