Actually make a library and start sketching out the interface

agb-image-converter/src/lib.rs

@@ -0,0 +1,41 @@
+#[derive(Debug, Clone, Copy)]
+pub struct Colour {
+    r: u8,
+    g: u8,
+    b: u8,
+}
+
+impl Colour {
+    pub fn from_rgb(r: u8, g: u8, b: u8) -> Self {
+        Colour { r, g, b }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum TileSize {
+    Tile8,
+    Tile16,
+}
+
+pub struct ImageConverter {}
+
+pub struct ImageConverterConfigBuilder {
+    transparent_colour: Option<Colour>,
+    tile_size: TileSize,
+}
+
+impl ImageConverterConfigBuilder {
+    pub fn new_with_tile_size(tile_size: TileSize) -> Self {
+        ImageConverterConfigBuilder {
+            tile_size,
+            transparent_colour: None,
+        }
+    }
+
+    pub fn with_transparent_colour(&self, transparent_colour: Colour) -> Self {
+        ImageConverterConfigBuilder {
+            transparent_colour: Some(transparent_colour),
+            ..*self
+        }
+    }
+}

agb-image-converter/src/main.rs

@@ -1,3 +0,0 @@
-fn main() {
-    println!("Hello, world!");
-}