new file mode 100644
--- /dev/null
+++ b/.hgignore
@@ -0,0 +1,1 @@
+^target/

new file mode 100644
--- /dev/null
+++ b/Cargo.toml
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+[package]
+name = "image-resizer"
+version = "0.1.0"
+edition = "2018"
+authors = ["Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>"]
+description = "Resizer of PNGs and JPEGs"
+homepage = "https://linkmauve.fr/dev/image-resizer"
+repository = "https://hg.linkmauve.fr/image-resizer"
+keywords = ["image", "resizer", "png", "jpeg"]
+license = "MPL-2.0"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+image = { version = "0.23", default-features = false, features = ["png", "jpeg"] }
+log = "0.4"

new file mode 100644
--- /dev/null
+++ b/src/main.rs
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+use image::{imageops::FilterType, io::Reader as ImageReader};
+use log::info;
+use std::env;
+use std::error::Error;
+use std::path::Path;
+use std::str::FromStr;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let args: Vec<_> = env::args().collect();
+    if args.len() != 4 {
+        eprintln!("Usage: {} <size> <input> <output>", args[0]);
+        std::process::exit(1);
+    }
+
+    // Parse the arguments.
+    let size = u32::from_str(&args[1])?;
+    let input = Path::new(&args[2]);
+    let output = Path::new(&args[3]);
+
+    let (width, height) = image::image_dimensions(input)?;
+    if width < size && height < size {
+        info!(
+            "Input is already smaller than {}×{}, copying as is.",
+            size, size
+        );
+        std::fs::copy(input, output)?;
+        return Ok(());
+    }
+
+    // Open the image file.
+    let reader = ImageReader::open(input)?;
+
+    // Extract the guessed format, or panic if unknown/unsupported.
+    let format = reader.format().expect("Unsupported format in input file");
+
+    // Decode the image.
+    let image = reader.decode()?;
+
+    // Resize it to the requested size.
+    let image = image.resize(size, size, FilterType::Triangle);
+
+    // Then save it to the output.
+    image.save_with_format(output, format)?;
+
+    info!("Successfully resized!");
+    Ok(())
+}