Bump Rust to 2021 edition

Cargo.toml

@@ -1,6 +1,7 @@
 [package]
 name = "pixelpwnr"
 version = "0.1.0"
+edition = "2021"
 authors = ["Tim Visée <timvisee@gmail.com>"]
 license = "GPL-3.0"
 readme = "README.md"

src/arg_handler.rs

@@ -1,6 +1,3 @@
-extern crate clap;
-extern crate num_cpus;
-
 use clap::Parser;
 
 #[derive(Parser)]

src/image_manager.rs

@@ -3,12 +3,10 @@ use std::path::Path;
 use std::thread::sleep;
 use std::time::Duration;
 
-use image;
+use crate::pix::canvas::Canvas;
 use image::imageops::FilterType;
 use image::DynamicImage;
 
-use pix::canvas::Canvas;
-
 /// A manager that manages all images to print.
 pub struct ImageManager {
     images: Vec<DynamicImage>,

src/main.rs

@@ -1,7 +1,3 @@
-extern crate clap;
-extern crate image;
-extern crate rayon;
-
 mod arg_handler;
 mod color;
 mod image_manager;

src/painter/handle.rs

@@ -1,11 +1,9 @@
-extern crate image;
-
 use std::sync::mpsc::Sender;
 use std::thread::JoinHandle;
 
 use image::DynamicImage;
 
-use rect::Rect;
+use crate::rect::Rect;
 
 /// A handle to a painter thread.
 ///

src/painter/painter.rs

@@ -3,9 +3,9 @@ use std::sync::mpsc::Receiver;
 
 use image::{DynamicImage, Pixel};
 
-use color::Color;
-use pix::client::Client;
-use rect::Rect;
+use crate::color::Color;
+use crate::pix::client::Client;
+use crate::rect::Rect;
 
 /// A painter that paints on a pixelflut panel.
 pub struct Painter {

src/pix/canvas.rs

@@ -5,10 +5,10 @@ use std::time::Duration;
 
 use image::DynamicImage;
 
-use painter::handle::Handle;
-use painter::painter::Painter;
-use pix::client::Client;
-use rect::Rect;
+use crate::painter::handle::Handle;
+use crate::painter::painter::Painter;
+use crate::pix::client::Client;
+use crate::rect::Rect;
 
 /// A pixflut instance
 pub struct Canvas {

src/pix/client.rs

@@ -1,14 +1,11 @@
-extern crate bufstream;
-extern crate regex;
-
 use std::io::prelude::*;
 use std::io::{Error, ErrorKind};
 use std::net::TcpStream;
 
-use self::bufstream::BufStream;
-use self::regex::Regex;
+use bufstream::BufStream;
+use regex::Regex;
 
-use color::Color;
+use crate::color::Color;
 
 // The default buffer size for reading the client stream.
 // - Big enough so we don't have to expand