Generate Scalebar Overlay
This function creates an overlay with a scale bar of a user-specified length. It uses the coordinates of the map (specified by passing an extent) and then creates a scale bar at a specified x/y proportion across the map. If the map is not projected (i.e. is in lat/long coordinates) this function will use the 'geosphere' package to create a scale bar of the proper length.
generate_scalebar_overlay( extent, length, x = 0.05, y = 0.05, latlong = FALSE, thickness = NA, bearing = 90, unit = "m", flip_ticks = FALSE, labels = NA, text_size = 1, decimals = 0, text_offset = 1, adj = 0.5, heightmap = NULL, width = NA, height = NA, color1 = "white", color2 = "black", text_color = "black", font = 1, border_color = "black", tick_color = "black", border_width = 1, tick_width = 1, halo_color = NA, halo_expand = 1, halo_alpha = 1, halo_offset = c(0, 0), halo_blur = 1 )
extent |
A 'raster::Extent' object with the bounding box for the height map used to generate the original map. If this is in lat/long coordinates, be sure to set 'latlong = TRUE'. |
length |
The length of the scale bar, in 'units'. This should match the units used on the map, unless 'extent' uses lat/long coordinates. In that case, the distance should be in meters. |
x |
Default '0.05'. The x-coordinate of the bottom-left corner of the scale bar, as a proportion of the full map width. |
y |
Default '0.05'. The y-coordinate of the bottom-left corner of the scale bar, as a proportion of the full map height. |
latlong |
Default 'FALSE'. Set to 'TRUE' if the map is in lat/long coordinates to get an accurate scale bar (using distance calculated with the 'geosphere' package). |
thickness |
Default 'NA', automatically computed as 1/20th the length of the scale bar. Width of the scale bar. |
bearing |
Default '90', horizontal. Direction (measured from north) of the scale bar. |
unit |
Default 'm'. Displayed unit on the scale bar. |
flip_ticks |
Default 'FALSE'. Whether to flip the ticks to the other side of the scale bar. |
labels |
Default 'NA'. Manually specify the three labels with a length-3 character vector. Use this if you want display units other than meters. |
text_size |
Default '1'. Text size. |
decimals |
Default '0'. Number of decimal places for scale bar labels. |
text_offset |
Default '1'. Amount of offset to apply to the text from the scale bar, as a multiple of 'thickness'. |
adj |
Default '0.5', centered. Text justification. '0' is left-justified, and '1' is right-justified. |
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 'black'. Primary color of the scale bar. |
color2 |
Default 'white'. Secondary color of the scale bar. |
text_color |
Default 'black'. Text color. |
font |
Default '1'. An integer which specifies which font to use for text. If possible, device drivers arrange so that 1 corresponds to plain text (the default), 2 to bold face, 3 to italic and 4 to bold italic. |
border_color |
Default 'black'. Border color of the scale bar. |
tick_color |
Default 'black'. Tick color of the scale bar. |
border_width |
Default '1'. Width of the scale bar border. |
tick_width |
Default '1'. Width of the tick. |
halo_color |
Default 'NA', no halo. If a color is specified, the text label 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, as a proportion of the full scene. |
halo_blur |
Default ‘1'. Amount of blur to apply to the halo. Values greater than '30' won’t result in further blurring. |
Semi-transparent overlay with a scale bar.
#Only run these examples if the `magick` package is installed.
if ("magick" %in% rownames(utils::installed.packages())) {
#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)
#For convenience, the extent of the montereybay dataset is included as an attribute
mb_extent = attr(montereybay, "extent")
#Add a scalebar
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 40000,
heightmap = montereybay,
latlong=TRUE)) %>%
plot_map()
#Change the text color
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 40000,
text_color = "white",
heightmap = montereybay,
latlong=TRUE)) %>%
plot_map()
#Change the length
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 30000,
text_color = "white",
heightmap = montereybay,
latlong=TRUE)) %>%
plot_map()
#Change the thickness (default is length/20)
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 30000,
text_color = "white", thickness = 30000/10,
heightmap = montereybay,
latlong=TRUE)) %>%
plot_map()
#Change the text offset (given in multiples of thickness)
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 30000,
text_color = "white", thickness = 30000/10,
text_offset = 0.75,
heightmap = montereybay,
latlong=TRUE)) %>%
plot_map()
#Change the primary and secondary colors, along with the border and tick color
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 30000,
text_color = "white", border_color = "white",
tick_color = "white",
color1 = "darkolivegreen4", color2 = "burlywood3",
heightmap = montereybay,
latlong=TRUE)) %>%
plot_map()
#Add a halo
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 40000,
halo_color = "white", halo_expand = 1,
heightmap = montereybay,
latlong=TRUE)) %>%
plot_map()
#Change the orientation, position, text alignment, and flip the ticks to the other side
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 40000, x = 0.07,
bearing=0, adj = 0, flip_ticks = TRUE,
halo_color = "white", halo_expand = 1.5,
heightmap = montereybay,
latlong=TRUE)) %>%
plot_map()
#64373.8 meters in 40 miles
#Create custom labels, change font and text size, remove the border/ticks, and change the color
#Here, we specify a width and height to double the resolution of the image (for sharper text)
base_map %>%
add_overlay(generate_scalebar_overlay(extent = mb_extent, length = 64373.8, x = 0.07,
labels = c("0", "20", "40 miles"), thickness=2500,
text_size=3, font = 2, text_offset = 0,
text_color="white", color2="#bf323b", border_color=NA,
tick_color="red", tick_width=0,
bearing=0, adj = 0, flip_ticks = TRUE,
halo_color="black", halo_blur=3, halo_alpha=0.5,
width = ncol(montereybay)*2,
height = nrow(montereybay)*2,
latlong=TRUE), rescale_original=TRUE) %>%
plot_map()
}Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.