Animation example of multithreaded raster processing using {stars} in R

animate_stars.R

library("sf")
library("stars")
library("gganimate")
library("ggnewscale")

tif = system.file("tif/L7_ETMs.tif", package = "stars")
bands = paste0("B", c(1:5, 7))
r = read_stars(tif)
r = st_set_dimensions(r, 3, values = bands, names = "band")
r_bbox = st_as_sfc(st_bbox(r))

blocks = st_make_grid(r, cellsize = c(2048, 2048))
blocks = st_intersection(blocks, r_bbox)
blocks = st_as_sf(blocks)
blocks$cpu = rep(1:5, times = 5)
blocks$iter = rep(1:5, each = 5)
# blocks$iter = sample(1:7, 49, replace = TRUE) # random order

r_df = as.data.frame(split(r))
r_df$rgb = rgb(r_df$B3, r_df$B2, r_df$B1, maxColorValue = 255)

p = ggplot() +
  geom_raster(data = r_df, aes(x = x, y = y, fill = rgb)) +
  labs(title = "Parallel processing") +
  scale_fill_identity() +
  new_scale_fill() +
  geom_sf(data = blocks, aes(fill = as.factor(cpu)), alpha = 0.3) +
  scale_fill_brewer(palette = "Set1", name = "CPU") +
  transition_manual(iter, cumulative = TRUE) +
  theme_void() +
  theme(
    plot.title = element_text(size = 26, face = "bold", hjust = 0.5)
  )
animate(p)

anim_save("gif.gif", p)