Transforms an input `sf` object into an image overlay for the current height map.
generate_polygon_overlay(
geometry,
extent,
heightmap = NULL,
width = NA,
height = NA,
resolution_multiply = 1,
offset = c(0, 0),
data_column_fill = NULL,
linecolor = "black",
palette = "white",
linewidth = 1
)Arguments
- geometry
An `sf` object with POLYGON geometry.
- extent
Either an object representing the spatial extent of the scene (either from the `raster`, `terra`, `sf`, or `sp` packages), a length-4 numeric vector specifying `c("xmin", "xmax","ymin","ymax")`, or the spatial object (from the previously aforementioned packages) which will be automatically converted to an extent object.
- heightmap
Default `NULL`. The original height map. Pass this in to extract the dimensions of the resulting overlay automatically.
- width
Default `NA`. Width of the resulting overlay. Default the same dimensions as height map.
- height
Default `NA`. Width of the resulting overlay. Default the same dimensions as height map.
- resolution_multiply
Default `1`. If passing in `heightmap` instead of width/height, amount to increase the resolution of the overlay, which should make lines/polygons/text finer. Should be combined with `add_overlay(rescale_original = TRUE)` to ensure those added details are captured in the final map.
- offset
Default `c(0,0)`. Horizontal and vertical offset to apply to the polygon, in units of `geometry`.
- data_column_fill
Default `NULL`. The column to map the polygon fill color to.
- linecolor
Default `black`. Color of the lines.
- palette
Default `black`. Single color, named vector color palette, or palette function. If this is a named vector and `data_column_fill` is not `NULL`, it will map the colors in the vector to the names. If `data_column_fill` is a numeric column, this will give a continuous mapping.
- linewidth
Default `1`. Line width.
Value
Image overlay representing the input polygon data.
Examples
#Plot the counties around Monterey Bay, CA
if(run_documentation()) {
generate_polygon_overlay(monterey_counties_sf, palette = rainbow,
extent = attr(montereybay,"extent"), heightmap = montereybay) %>%
plot_map()
}
if(run_documentation()) {
#These counties include the water, so we'll plot bathymetry data over the polygon
#data to only include parts of the polygon that fall on land.
water_palette = colorRampPalette(c("darkblue", "dodgerblue", "lightblue"))(200)
bathy_hs = height_shade(montereybay, texture = water_palette)
generate_polygon_overlay(monterey_counties_sf, palette = rainbow,
extent = attr(montereybay,"extent"), heightmap = montereybay) %>%
add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
plot_map()
}
if(run_documentation()) {
#Add a semi-transparent hillshade and change the palette, and remove the polygon lines
montereybay %>%
sphere_shade(texture = "bw") %>%
add_overlay(generate_polygon_overlay(monterey_counties_sf,
palette = terrain.colors, linewidth=NA,
extent = attr(montereybay,"extent"), heightmap = montereybay),
alphalayer=0.7) %>%
add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
add_shadow(ray_shade(montereybay,zscale=50),0) %>%
plot_map()
}
if(run_documentation()) {
#Map one of the variables in the sf object and use an explicitly defined color palette
county_palette = c("087" = "red", "053" = "blue", "081" = "green",
"069" = "yellow", "085" = "orange", "099" = "purple")
montereybay %>%
sphere_shade(texture = "bw") %>%
add_shadow(ray_shade(montereybay,zscale=50),0) %>%
add_overlay(generate_polygon_overlay(monterey_counties_sf, linecolor="white", linewidth=3,
palette = county_palette, data_column_fill = "COUNTYFP",
extent = attr(montereybay,"extent"), heightmap = montereybay),
alphalayer=0.7) %>%
add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
add_shadow(ray_shade(montereybay,zscale=50),0.5) %>%
plot_map()
}
