From this URL, we remove the sidebar, and full-screen screenshot to this local PNG file, then georef from the url
https://tasmap.org/#9/-42.8830/147.0026
The file read here with rast() can be read directly with this, or itis attached below.
r <- rast("/vsicurl/https://private-user-images.githubusercontent.com/4107631/479547609-2127f648-d117-457b-ba01-6b181cdd5843.png?jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.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.0TjLYya2nBjCNiO9po3uqGNK47gdW9b9x1JJPAiipXM")
## this URL and this screenshot are intimately tied, I screenshot at full screen with sidebar removed (title bar is 50 pixels, which we subtract below)
url <- "https://tasmap.org/#9/-42.8830/147.0026"
r <- terra::rast("2025-08-19 23_53_47-TasMap.org.png")
r <- terra::flip(r, "vertical")
## drop the top 50 rows (before we set the extent)
r <- terra::crop(r, terra::ext(0, ncol(r), 0, nrow(r) - 50))
tx <- strsplit(url, "/")
z <- as.integer(gsub("#", "", tx[[1]][[4]]))
ll <- matrix(as.numeric(unlist(tx[[1]][6:5])), ncol = 2)
crs <- "EPSG:3857"
## this is the centre point
xy <- terra::project(ll, to = crs, from = "EPSG:4326")
## this is the number of pixels
dm <- dim(r)[2:1]
## zero scale
z0 <- 20037508 * 2 / 256
## so width,height of image is
wh <- dm * z0 / (2^z)
## so extent of it is
ex <- rep(xy, each = 2L) + c(-1, 1, -1, 1) * rep(wh, each = 2L)/2
terra::ext(r) <- terra::ext(ex)
terra::crs(r) <- crs
plotRGB(r, asp = 1)
m <- do.call(cbind, maps::map(plot = F)[1:2])
lines(project(m, to = crs, from = "EPSG:4326"), lwd = 4, col = "firebrick")
