On 27 Jan. 2022 my package rasterpic was accepted on CRAN (Hooray!). This package geotags images, using a spatial object (from sf or terra) as a geographic reference.
I tweeted about that, and it seems to have received good feedback from the #rspatial community:
#rspatial Do we need a package for using our own pictures as base maps? I don’t know, but anyway we have it! {rasterpic} 📦 is now on CRAN, and we can convert our pngs to spatial rasters like this https://t.co/fpoollARoN pic.twitter.com/l9o7rQwdgX
— dieghernan ن (@dhernangomez) January 27, 2022
I also received an interesting reply to this from Hefin Ioan Rhys @HRJ21:
Ooh I think a map with countries filled with their own flag would be poppin'.
— Hefin Ioan Rhys (@HRJ21) January 28, 2022
That reminds me of a previous post that I wrote when I added some new functions to the cartography package, now replaced by the mapsf package.
With rasterpic, we now have an alternative tool for creating maps using images, and this quick post shows you how to do it.
I will replicate the Africa map presented in my previous plot, but this time I
will use newer packages, such as
giscoR, and the development
version of ggspatial
(not released yet), which adds support for SpatRaster objects in ggplot2.
The flags will be extracted from the GitHub repository
https://github.com/hampusborgos/country-flags.
# Development version of ggspatial
# devtools::install_github("paleolimbot/ggspatial")
library(ggspatial)
library(ggplot2)
library(giscoR)
library(dplyr)
library(rasterpic)
# For country names
library(countrycode)
world <- gisco_get_countries(epsg = 3857)
africa <- gisco_get_countries(region = "Africa", epsg = 3857)
# Base map of Africa
plot <- ggplot(world) +
geom_sf(fill = "grey90") +
theme_minimal() +
theme(panel.background = element_rect(fill = "lightblue"))
plot +
# Zoom on Africa
coord_sf(
xlim = c(-2000000, 6000000),
ylim = c(-4000000, 5000000)
)
Now, let’s add the flags with a loop:
# We paste the ISO2 code to each African country
africa$iso2 <- countrycode(africa$ISO3_CODE, "iso3c", "iso2c")
# Get flags from repo - low quality to speed up the code
flagrepo <- "https://raw.githubusercontent.com/hjnilsson/country-flags/master/png250px/"
# Loop and add
for (iso in africa$iso2) {
# Download pic and plot
imgurl <- paste0(flagrepo, tolower(iso), ".png")
tmpfile <- tempfile(fileext = ".png")
download.file(imgurl, tmpfile, quiet = TRUE, mode = "wb")
# Raster
x <- africa %>% filter(iso2 == iso)
x_rast <- rasterpic_img(x, tmpfile, crop = TRUE, mask = TRUE)
plot <- plot + layer_spatial(x_rast)
}
plot +
geom_sf(data = africa, fill = NA) +
# Zoom on Africa
coord_sf(
xlim = c(-2000000, 6000000),
ylim = c(-4000000, 5000000)
)
