Add a GeoTIFF file to a leaflet map using optimised rendering.
Add a GeoTIFF file to a leaflet map using optimised rendering.
addGeotiff( map, file = NULL, url = NULL, group = NULL, layerId = NULL, resolution = 96, opacity = 0.8, options = leaflet::tileOptions(), colorOptions = NULL, pixelValuesToColorFn = NULL, ... )
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 |
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). |
opacity |
opacity of the rendered layer. |
options |
options to be passed to the layer.
See |
colorOptions |
list defining the palette, breaks and na.color to be used. |
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. |
... |
currently not used. |
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.
A leaflet map object.
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)
myCustomJSFunc = htmlwidgets::JS(
"
pixelValuesToColorFn = (raster, colorOptions) => {
const cols = colorOptions.palette;
var scale = chroma.scale(cols);
if (colorOptions.breaks !== null) {
scale = scale.classes(colorOptions.breaks);
}
var pixelFunc = values => {
let clr = scale.domain([raster.mins, raster.maxs]);
if (isNaN(values)) return colorOptions.naColor;
return clr(values).hex();
};
return pixelFunc;
};
"
)
leaflet() %>%
addTiles() %>%
addGeotiff(
file = tmpfl
, opacity = 0.9
, colorOptions = colorOptions(
palette = grey.colors
, na.color = "transparent"
)
, pixelValuesToColorFn = myCustomJSFunc
)
}Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.