Creating a CLI using the library

Let's now use the library we created in our small CLI app.

✅ In cli/Cargo.toml, add:

[dependencies]
rustagram2 = "2"
image-manipulation = { path = "../image-manipulation" }

✅ Recreate parts of the main function:

use image_manipulation::apply_filter;
use rustagram::FilterType;

fn main() {
    let mut args = std::env::args().skip(1);
    let input = args.next().expect("INPUT required");
    let filter = args.next().expect("FILTER required");
    let output = args.next().unwrap_or_else(|| "output.jpg".to_string());

    let filter_type: FilterType = filter.parse().expect("can't parse filter name");
}

As our image manipulation library does not handle IO, we will reach for the std::fs::{read,write} function.

✅ Read the image as input

let bytes: Vec<u8> = std::fs::read(input).unwrap();

The type annotation here isn't strictly necessary and is generally omitted, but helps during explaining the example.

✅ Call the apply_filter library function

let manipulated_image = apply_filter(&bytes, filter_type);

Note the referencing sigil in front of bytes.

✅ Write the output to disk

std::fs::write(output, manipulated_image).unwrap();

Some ideas on what to do next:

• Instead of unwrapping all errors, handle Result otherwise
• Enable logging in the CLI binary - try out a few different logging crates