initial

Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "black-and-white-rainbows"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+hsl = "0.1.1"
+image = "0.25.5"
+itertools = "0.13.0"

src/main.rs

@@ -0,0 +1,72 @@
+use std::{collections::HashMap, env};
+
+use hsl::HSL;
+use image::{GenericImage, GenericImageView, Pixel, Rgb, Rgba};
+use itertools::Itertools;
+
+#[allow(clippy::many_single_char_names)]
+fn main() {
+    let mut args = env::args().skip(1);
+
+    let in_path = args.next().expect("i need a PATH. now!");
+    let start_x = args
+        .next()
+        .and_then(|n| n.parse::<i32>().ok())
+        .expect("start x");
+    let start_y = args
+        .next()
+        .and_then(|n| n.parse::<i32>().ok())
+        .expect("start y");
+    let out_path = args.next().expect("out path");
+
+    let mut img = image::open(in_path).expect("i wanna open an image");
+
+    // let's just hsl-rotate floodfill first
+    let mut covered = HashMap::new();
+    covered.insert((start_x, start_y), HSL::from_rgb(&[255, 0, 0]));
+
+    // TODO: hold front and covered. duh
+    // scale based on longest path (ez)
+    loop {
+        let mut front = HashMap::new();
+        for ((x, y), hsl) in &covered {
+            for (dx, dy) in (-1..=1).cartesian_product(-1..=1) {
+                let (x, y) = (x + dx, y + dy);
+                let Ok(x_idx) = x.try_into() else {
+                    break;
+                };
+                let Ok(y_idx) = y.try_into() else {
+                    break;
+                };
+
+                if img.in_bounds(x_idx, y_idx)
+                    && !is_dark(img.get_pixel(x_idx, y_idx).to_rgb())
+                    && !covered.contains_key(&(x, y))
+                {
+                    let mut color = *hsl;
+                    color.h += 1.;
+                    if color.h >= 360. {
+                        color.h = 0.;
+                    }
+                    let (r, g, b) = color.to_rgb();
+
+                    img.put_pixel(x_idx, y_idx, Rgba([r, g, b, 255]));
+                    front.insert((x, y), color);
+                }
+            }
+        }
+
+        if front.is_empty() {
+            break;
+        }
+
+        covered.extend(front);
+    }
+
+    img.save(out_path).expect("tried to save :(");
+}
+
+fn is_dark(pixel: Rgb<u8>) -> bool {
+    let Rgb([r, g, b]) = pixel;
+    r < 127 && g < 127 && b < 127
+}