Generate Compass Overlay

This adds the compass

Based on code from "Auxiliary Cartographic Functions in R: North Arrow, Scale Bar, and Label with a Leader Arrow"

generate_compass_overlay(
  x = 0.85,
  y = 0.15,
  size = 0.05,
  text_size = 1,
  bearing = 0,
  heightmap = NULL,
  width = NA,
  height = NA,
  resolution_multiply = 1,
  color1 = NA,
  color2 = NA,
  text_color = NA,
  border_color = "black",
  border_width = 1,
  compass_type = c("classic", "split_arrow", "triangle_circle", "split_arrow_ring"),
  halo_color = NA,
  halo_expand = 2,
  halo_alpha = 1,
  halo_offset = c(0, 0),
  halo_blur = 0,
  halo_edge_softness = 0.1
)

Arguments

x

Default NULL. The horizontal percentage across the map (measured from the bottom-left corner) where the compass is located.

y

Default NULL. The vertical percentage across the map (measured from the bottom-left corner) where the compass is located.

size

Default 0.05. Size of the compass, in percentage of the map size..

text_size

Default 1. Text size.

bearing

Default 0. Angle (in degrees) of north.

heightmap

Default NULL. The original height map. Pass this in to extract the dimensions of the resulting RGB image array automatically.

width

Default NA. Width of the resulting image array. Default the same dimensions as height map.

height

Default NA. Width of the resulting image array. 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 finer. Should be combined with add_overlay(rescale_original = TRUE) to ensure those added details are captured in the final map.

color1

Default NA, white except for compass_type == "triangle_circle" . Primary color of the compass.

color2

Default NA, black. Secondary color of the symcompass.

text_color

Default black. Text color.

border_color

Default black. Border color of the scale bar.

border_width

Default 1. Width of the scale bar border.

compass_type

Default "classic". Set to "split_arrow", "triangle_circle", or "split_arrow_ring" to draw simple polygon north arrows that match the styles shown above.

halo_color

Default NA, no halo. If a color is specified, the compass will be surrounded by a halo of this color.

halo_expand

Default 1. Number of pixels to expand the halo.

halo_alpha

Default 1. Transparency of the halo.

halo_offset

Default c(0,0). Horizontal and vertical offset to apply to the halo, in percentage of the image.

halo_blur

Default 1. Amount of blur to apply to the halo. Values greater than 30 won't result in further blurring.

halo_edge_softness

Default 0.1. Width of the softened halo edge transition, in pixels.

Value

Semi-transparent overlay with a compass.

Examples

if(run_documentation()) {
#Create the water palette
water_palette = colorRampPalette(c("darkblue", "dodgerblue", "lightblue"))(200)
bathy_hs = height_shade(montereybay, texture = water_palette)

#Generate flat water heightmap
mbay = montereybay
mbay[mbay < 0] = 0

base_map = mbay |>
 height_shade() |>
 add_overlay(generate_altitude_overlay(bathy_hs, montereybay, 0, 0))  |>
 add_shadow(lamb_shade(montereybay,zscale=50),0.3)

#Plot a compass
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay)) |>
 plot_map()
}


if(run_documentation()) {
#Change the position to be over the water
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15)) |>
 plot_map()
}

if(run_documentation()) {
#Change the type
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15,
                                      compass_type = "split_arrow")) |>
 plot_map()
}

if(run_documentation()) {
#Change the type
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15,
                                      compass_type = "split_arrow_ring")) |>
 plot_map()
}

if(run_documentation()) {
#Change the type
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15,
                                      compass_type = "triangle_circle")) |>
 plot_map()
}

if(run_documentation()) {
#Change the text color for visibility
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, compass_type = "split_arrow",
x = 0.15, text_color="white")) |>
 plot_map()
}

if(run_documentation()) {
#Alternatively, add a halo color to improve contrast
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             compass_type = "split_arrow", halo_color="white", halo_expand = 2)) |>
 plot_map()
}

if(run_documentation()) {
#Change the color scheme
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             compass_type = "split_arrow", halo_color="white",
             halo_expand = 2, color1 = "purple", color2 = "red")) |>
 plot_map()
}

if(run_documentation()) {
#Remove the inner border
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             border_color=NA,compass_type = "split_arrow",
             halo_color="white", halo_expand = 2,
             color1 = "darkolivegreen4", color2 = "burlywood3")) |>
 plot_map()
}

if(run_documentation()) {
#Change the size of the compass and text
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.75, y=0.75,
             halo_color="white", halo_expand = 2,compass_type = "classic",
             size=0.075*2, text_size = 1.25)) |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.45, y=0.45,
             halo_color="white", halo_expand = 2,compass_type = "split_arrow_ring",
             size=0.075)) |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             halo_color="white", halo_expand = 2,compass_type = "split_arrow",
             size=0.075/2, text_size = 0.75)) |>
 plot_map()
}

if(run_documentation()) {
#Change the bearing of the compass
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             halo_color="white", halo_expand = 2, bearing=30, compass_type = "classic",
             size=0.075)) |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.35, y=0.15,
             halo_color="white", halo_expand = 2, bearing=15, compass_type = "triangle_circle",
             size=0.075)) |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.35,
             halo_color="white", halo_expand = 2, bearing=-45, compass_type = "split_arrow_ring",
             size=0.075)) |>
 plot_map()
}

if(run_documentation()) {
#Create a drop shadow effect
base_map |>
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             text_color="white", halo_alpha=0.7, halo_blur=3,
             halo_color="black", halo_expand = 2, halo_offset = c(0.002,-0.002))) |>
add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.35, y=0.15,
             text_color="white", halo_alpha=0.7, halo_blur=3,
             compass_type = "split_arrow",
             halo_color="black", halo_expand = 2, halo_offset = c(0.002,-0.002))) |>
add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.35,
             text_color="white", halo_alpha=0.2, halo_blur=8,
             compass_type = "split_arrow_ring",
             halo_color="white", halo_expand = 2)) |>
 plot_map()
}