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 = 0.075,
  text_size = 1,
  bearing = 0,
  heightmap = NULL,
  width = NA,
  height = NA,
  color1 = "white",
  color2 = "black",
  text_color = "black",
  border_color = "black",
  border_width = 1,
  halo_color = NA,
  halo_expand = 1,
  halo_alpha = 1,
  halo_offset = c(0, 0),
  halo_blur = 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.

color1

Default `white`. Primary color of the compass.

color2

Default `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.

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.

Value

Semi-transparent overlay with a compass.

Examples

#Only run these examples if the `magick` package is installed.
if (length(find.package("magick", quiet = TRUE)) > 0) {
# \donttest{
#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()
 
#Change the position to be over the water
base_map %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15)) %>% 
 plot_map()
 
#Change the text color for visibility
base_map %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, text_color="white")) %>% 
 plot_map()
 
#Alternatively, add a halo color to improve contrast
base_map %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             halo_color="white", halo_expand = 1)) %>% 
 plot_map()
 
#Alternatively, add a halo color to improve contrast
base_map %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             halo_color="white", halo_expand = 1)) %>% 
 plot_map()
 
#Change the color scheme
base_map %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             halo_color="white", halo_expand = 1, color1 = "purple", color2 = "red")) %>% 
 plot_map()
 
#Remove the inner border
base_map %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             border_color=NA,
             halo_color="white", halo_expand = 1, 
             color1 = "darkolivegreen4", color2 = "burlywood3")) %>% 
 plot_map()
 
#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 = 1, 
             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 = 1, 
             size=0.075)) %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             halo_color="white", halo_expand = 1, 
             size=0.075/2, text_size = 0.75)) %>% 
 plot_map()
 
#Change the bearing of the compass
base_map %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.85, y=0.85,
             halo_color="white", halo_expand = 1, bearing=30,
             size=0.075)) %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.5, y=0.5,
             halo_color="white", halo_expand = 1, bearing=15,
             size=0.075)) %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, x = 0.15, y=0.15,
             halo_color="white", halo_expand = 1, bearing=-45,
             size=0.075)) %>% 
 plot_map()
 
#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=0.5, halo_blur=2,
             halo_color="black", halo_expand = 1, halo_offset = c(0.003,-0.003))) %>% 
 plot_map()
# }
}