geom_spatraster_rgb {tidyterra}

Visualise SpatRaster objects as images

Description

This geom is used to visualise SpatRaster objects (see terra::rast()) as RGB images. The layers are combined such that they represent the red, green and blue channel.

For plotting SpatRaster objects by layer values use geom_spatraster().

The underlying implementation is based on ggplot2::geom_raster().

Usage

geom_spatraster_rgb(
  mapping = aes(),
  data,
  interpolate = TRUE,
  r = 1,
  g = 2,
  b = 3,
  alpha = 1,
  maxcell = 5e+05,
  max_col_value = 255,
  ...
)

Arguments

mapping

Ignored.

data

A SpatRaster object.

interpolate

If TRUE interpolate linearly, if FALSE (the default) don't interpolate.

r, g, b

Integer representing the number of layer of data to be considered as the red (r), green (g) and blue (b) channel.

alpha

The alpha transparency, a number in [0,1], see argument alpha in hsv.

maxcell

positive integer. Maximum number of cells to use for the plot.

max_col_value

Number giving the maximum of the color values range. When this is 255 (the default), the result is computed most efficiently. See grDevices::rgb().

...

Other arguments passed on to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like colour = "red" or size = 3. They may also be parameters to the paired geom/stat.

Value

A ggplot2 layer

terra equivalent

terra::plotRGB()

Aesthetics

No aes() is required. In fact, aes() will be ignored.

Coords

When the SpatRaster does not present a crs (i.e., terra::crs(rast) == "") the geom does not make any assumption on the scales.

On SpatRaster that have a crs, the geom uses ggplot2::coord_sf() to adjust the scales. That means that also the SpatRaster may be reprojected.

Source

Based on the layer_spatial() implementation on ggspatial package. Thanks to Dewey Dunnington and ggspatial contributors.

See Also

ggplot2::geom_raster(), ggplot2::coord_sf(), grDevices::rgb().

You can get also RGB tiles from the maptiles package, see maptiles::get_tiles().

Other ggplot2 utils: autoplot.Spat, fortify.Spat, geom_spat_contour, geom_spatraster(), ggspatvector, stat_spat_coordinates()

Examples

# Tile of Castille and Leon (Spain) from OpenStreetMap
file_path <- system.file("extdata/cyl_tile.tif", package = "tidyterra")

library(terra)
tile <- rast(file_path)

library(ggplot2)


ggplot() +
  geom_spatraster_rgb(data = tile) +
  # You can use coord_sf
  coord_sf(crs = 3035)

# Combine with sf objects
vect_path <- system.file("extdata/cyl.gpkg", package = "tidyterra")

cyl_sf <- sf::st_read(vect_path)

ggplot(cyl_sf) +
  geom_spatraster_rgb(data = tile) +
  geom_sf(aes(fill = iso2)) +
  coord_sf(crs = 3857) +
  scale_fill_viridis_d(alpha = 0.7)