switch to fenix to manage rust toolchain in nix

Cargo.toml

@@ -11,6 +11,7 @@ path = "src/cli.rs"
 required-features = ["cli"]
 
 [dependencies]
+image = { version = "0.25.8", optional = true }
 rug = "1.27"
 
 [dependencies.clap]
@@ -21,3 +22,4 @@ optional = true
 [features]
 default = []
 cli = ["dep:clap"]
+image = ["dep:image"]

flake.lock

@@ -1,5 +1,26 @@
 {
   "nodes": {
+    "fenix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "rust-analyzer-src": "rust-analyzer-src"
+      },
+      "locked": {
+        "lastModified": 1761806629,
+        "narHash": "sha256-3u8345VliQtbpOtCNYYpDTCsjS8A9osrpU03E8TaIBw=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "c7c690951af16e60912678fab6155fb120cc27b0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1758690382,
@@ -18,8 +39,26 @@
     },
     "root": {
       "inputs": {
+        "fenix": "fenix",
         "nixpkgs": "nixpkgs"
       }
+    },
+    "rust-analyzer-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1761739801,
+        "narHash": "sha256-ONUpb+l5oEIb9iOGkmUhze5YjRexZ6sc3mwQyLXlcms=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "769ebafdc66559d620bdc414743f32bb28180c58",
+        "type": "github"
+      },
+      "original": {
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
+        "type": "github"
+      }
     }
   },
   "root": "root",

flake.nix

@@ -1,12 +1,30 @@
 {
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+
+    fenix = {
+      url = "github:nix-community/fenix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs =
-    { self, nixpkgs }:
+    {
+      self,
+      nixpkgs,
+      fenix,
+    }:
     let
       pkgs = nixpkgs.legacyPackages.x86_64-linux;
+      rustPkgs = fenix.packages.x86_64-linux.default;
+
+      rustPlatform = pkgs.makeRustPlatform {
+        inherit (rustPkgs)
+          cargo
+          rustc
+          ;
+      };
+
       nativeBuildInputs = with pkgs; [
         pkg-config
         m4
@@ -29,7 +47,7 @@
       };
 
       devShells.x86_64-linux.default = mkShell {
-        packages = [
+        packages = with rustPkgs; [
           cargo
           clippy
           rustc

src/lib.rs

@@ -1,3 +1,6 @@
+#[cfg(feature = "image")]
+use image::{ImageBuffer, Pixel};
+
 use rug::Integer as Int;
 
 #[derive(Debug)]
@@ -45,6 +48,7 @@ impl Dollcode {
         }
 
         out.reverse();
+
         Dollcode(out.into_iter().collect())
     }
 
@@ -94,8 +98,52 @@ impl Dollcode {
         }
 
         out.reverse();
+
         out.into_iter().collect()
     }
+
+    #[cfg(feature = "image")]
+    pub fn render_image<Pix>(&self) -> ImageBuffer<Pix, Vec<u8>>
+    where
+        Pix: Pixel<Subpixel = u8> + 'static,
+    {
+        let char_width = 16u32;
+        let char_height = char_width * 4u32;
+
+        let img_width = ((char_width * 2) * self.0.chars().count() as u32) - char_width;
+        let img_height = char_height;
+
+        let mut dark_pixel =
+            *Pix::from_slice(&vec![Pix::Subpixel::MIN; Pix::CHANNEL_COUNT as usize]);
+        let mut light_pixel =
+            *Pix::from_slice(&vec![Pix::Subpixel::MAX; Pix::CHANNEL_COUNT as usize]);
+
+        if matches!(Pix::CHANNEL_COUNT, 2 | 4) {
+            dark_pixel.channels_mut()[Pix::CHANNEL_COUNT as usize - 1] = Pix::Subpixel::MAX;
+            light_pixel.channels_mut()[Pix::CHANNEL_COUNT as usize - 1] = Pix::Subpixel::MIN;
+        }
+
+        let mut img = ImageBuffer::from_pixel(img_width, img_height, light_pixel);
+
+        for (i, ch) in self.0.chars().enumerate() {
+            let x_offset = (i as u32) * char_width * 2;
+
+            let (x, y, width, height) = match ch {
+                '▖' => (x_offset, char_height / 2, char_width, char_height / 2),
+                '▘' => (x_offset, 0, char_width, char_height / 2),
+                '▌' => (x_offset, 0, char_width, char_height),
+                _ => unreachable!(),
+            };
+
+            for y_ in y..(y + height) {
+                for x_ in x..(x + width) {
+                    img.put_pixel(x_, y_, dark_pixel)
+                }
+            }
+        }
+
+        img
+    }
 }
 
 impl std::str::FromStr for Dollcode {