How to convert a picture in pure black and white in Rust

Question

I want to convert a picture in pure black and white(e.g. no grayscale) using Image crate, the result should be a picture with 0 and 255 RGB values.

Following the docs i've wrote the following:

let img = image::open("photo.jpg").unwrap(); // Load picture
let gray_img = img.grayscale(); // Convert it

// Access a random pixel value
let px = gray_img.get_pixel(0,0);
println!("{:?}", pixel.data); // Print RGB array

The problem here is that, whatever pixel i print, it gives me grayscale value. So, is there a function to convert an image in pure black and white? Something like Pillow's convert function for Python?

Answer 1

Here's how you can first build a grayscale image then dither it to a Black and White one:

use image::{self, imageops::*};

let img = image::open("cat.jpeg").unwrap();
let mut img = img.grayscale();
let mut img = img.as_mut_luma8().unwrap();
dither(&mut img, &BiLevel);
img.save("cat.png").unwrap(); // this step is optional but convenient for testing

You should of course properly handle errors instead of just doing unwrap.