Generate Compass Overlay — generate_compass

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,
  resolution_multiply = 1,
  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.
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 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

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 text color for visibility
base_map %>% 
 add_overlay(generate_compass_overlay(heightmap = montereybay, 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,
             halo_color="white", halo_expand = 1)) %>% 
 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,
             halo_color="white", halo_expand = 1)) %>% 
 plot_map()
}

if(run_documentation()) {
#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()
}

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,
             halo_color="white", halo_expand = 1, 
             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 = 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()
}

if(run_documentation()) {
#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()
}

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=0.5, halo_blur=2,
             halo_color="black", halo_expand = 1, halo_offset = c(0.003,-0.003))) %>% 
 plot_map()
}