Plotters image artifacts

Cargo.toml

[package]
name = "plotters_artifacts_test"
version = "0.1.0"
edition = "2021"

[dependencies]
image = "0.25.6"
plotters = "0.3.7"
plotters-bitmap = "0.3.7"

main.rs

use image::{DynamicImage, RgbaImage};
use plotters::prelude::*;
use plotters_bitmap::BitMapBackend;

const WIDTH: u32 = 100;
const HEIGHT: u32 = 100;

fn main() {
    // Create an RGBA buffer
    let mut buffer = vec![0u8; (WIDTH * HEIGHT * 4) as usize];

    // Use Plotters to draw something on the buffer
    fill_buffer(&mut buffer);

    // Write the resulting image, again, based on RGBA buffer
    DynamicImage::ImageRgba8(RgbaImage::from_raw(WIDTH, HEIGHT, buffer).unwrap())
        .save("test.png")
        .unwrap();
}

fn fill_buffer(buffer: &mut Vec<u8>) {
    // Create a backend based on RGB buffer
    let backend = BitMapBackend::with_buffer(buffer, (WIDTH, HEIGHT));
    let root = backend.into_drawing_area();

    // Clear the background
    root.fill(&WHITE).unwrap();

    // Fill the left half of the area
    root.split_evenly((1, 2))[0].fill(&BLACK).unwrap();

    // Finish drawing
    root.present().unwrap();
}