diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..5c8091e
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,67 @@
+use std::{collections::{HashMap, HashSet}, env, num::ParseIntError};
+
+use dotenv::dotenv;
+use image::{DynamicImage, ImageReader, Rgb};
+
+type ColourSet = HashMap<u8, HashMap<u8, HashSet<u8>>>;
+type Colour = Rgb<u8>;
+
+pub fn decode_hex(s: &str) -> Result<Colour, ParseIntError> {
+    Ok(Rgb((0..s.len())
+        .step_by(2)
+        .map(|i| u8::from_str_radix(&s[i..i + 2], 16))
+        .collect())
+    )
+}
+
+fn extract_colours(img: DynamicImage) -> ColourSet {
+    todo!()
+}
+
+fn closest_colour(colour: Colour, all: &ColourSet) -> Option<Colour> {
+    // use redmean to calculate the distance between colours
+    // inevitably O(len(all))
+    let mut closest: Option<Colour> = None;
+    let mut dist: f32 = f32::MAX;
+    for (r, gbs) in all.iter() {
+        let r_bar = 0.5 * (r + colour[0]) as f32;
+        let delta_r = ((r + colour[0]) * (r + colour[0])) as f32;
+        for (g, bs) in gbs.iter() {
+            let delta_g = ((g + colour[1]) * (g + colour[1])) as f32;
+            for b in bs {
+                let delta_b = ((b + colour[2]) * (b + colour[2])) as f32;
+
+                let delta = (2.0 + r_bar/256.0) * delta_r + 4.0 * delta_g + (2.0 + (255.0 - r_bar)/256.0) * delta_b;
+                if delta < dist {
+                    dist = delta;
+                    closest = Some(Rgb([*r,*g,*b]));
+                }
+            }
+        }
+    }
+    return closest
+}
+
+
+fn main() {
+    dotenv().ok();
+    pretty_env_logger::init();
+
+    let args: Vec<String> = env::args().collect();
+    if args.len() > 1 {
+        let img_file = &args[1];
+        let img = ImageReader::open(img_file).unwrap().decode().unwrap(); // FIXME: unwraps
+
+        let all_cols = extract_colours(img);
+        let mut output_cols: HashMap<Colour, Colour> = HashMap::new();
+
+        for c_str in args {
+            // TODO: parse args
+            let c = decode_hex(&c_str).unwrap(); // FIXME: unwraps; 
+            if let Some(col) = closest_colour(c, &all_cols) {
+                output_cols.insert(c, col);
+            }
+        }
+
+    }
+}