Get external image file dimensions with base r - r

Question

Is it possible to get external image dimensions (for .png, .jpg, etc.) using base R? If not, what is the most lightweight R package that allows one to accomplish this?

Answer 1

Not base R, but the {magick} package does this easily. An example using a picture from the documentation:
library(magick)
frink <- image_read("https://jeroen.github.io/images/frink.png")
image_info(frink)
Output:
format width height colorspace matte filesize density
1 PNG 220 445 sRGB TRUE 73494 72x72

Answer 2

Here is a function inspired by r2evans suggestion to use the file system command:
png_url <- "https://static1.squarespace.com/static/5d2dfbe36a873f0001547453/t/5d2e5ab5607b8f00015901b6/1619287812905/?format=1500w"
jpg_url <- "https://guardian.ng/wp-content/uploads/2016/12/Rice-farm.jpg"
download.file(png_url, "test.png")
download.file(jpg_url, "test.jpg")
get_image_dimensions <- function(path) {
# Ensure file exists
if(!file.exists(path))
stop("No file found", call. = FALSE)
# Ensure file ends with .png or .jpg or jpeg
if (!grepl("\\.(png|jpg|jpeg)$", x = path, ignore.case = TRUE))
stop("File must end with .png, .jpg, or .jpeg", call. = FALSE)
# Get return of file system command
s <- system(paste0("file ", path), intern = TRUE)
# Extract width and height from string
width <- regmatches(s, gregexpr("(?<=, )[0-9]+(?=(x| x )[0-9]+,)", s, perl = TRUE))[[1]]
height <- regmatches(s, gregexpr(", [0-9]+(x| x )\\K[0-9]+(?=,)", s, perl = TRUE))[[1]]
setNames(as.numeric(c(width, height)), c("Width", "Height"))
}
get_image_dimensions('test.png')
#> Width Height
#> 1409 1046
get_image_dimensions('test.jpg')
#> Width Height
#> 1280 724
Created on 2021-06-11 by the reprex package (v1.0.0)