addGeotiff: Add a GeoTIFF file to a leaflet map using optimised...
In r-spatial/leafem: 'leaflet' Extensions for 'mapview'

addGeotiff

R Documentation

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,
  imagequery = TRUE,
  imagequeryOptions = NULL,
  ...
)

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/en/latest/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`
`imagequery`	If `TRUE` a leaflet control with the hovered/clicked value will appear on the map.
`imagequeryOptions`	additional options for the control panel.
`...`	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"
      )
    )

}

r-spatial/leafem documentation built on Nov. 1, 2024, 2:48 p.m.