Use leftover bits in HighestBits selector

squash/Cargo.toml

@@ -7,14 +7,14 @@ license = "ISC"
 description = "CLI tool for quantizing colours"
 repository = "https://github.com/gennyble/colorsquash/tree/main/squash"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
-[dependencies]
 # the meat 'o the thing! the meaning behind it all
-colorsquash = { path = "..", version = "0.2.0", default-features = false, features = [
-	"gifed",
-] }
+[dependencies.colorsquash]
+path = ".."
+version = "0.2.0"
+default-features = false # `kmeans` crate currently very broken
+features = ["gifed"]
 
+[dependencies]
 # just useful tools for writing binaries
 anyhow = "1.0.75"
 camino = "1.1.6"

src/selection.rs

@@ -337,17 +337,28 @@ pub struct HighestBits {}
 
 impl Selector for HighestBits {
 	fn select(&mut self, max_colors: usize, image: ImageData) -> Vec<RGB8> {
-		let max_bits = max_colors.next_power_of_two().ilog2() / 3;
-		let shift = 8 - max_bits;
+		let bits = max_colors.next_power_of_two().ilog2();
+		let leftover = bits % 3;
+		let shift = 8 - (bits / 3);
+
+		//TODO: gen- we're taking red/green here because, as i remember, they
+		// are the colours to which we are most sensetive? but it would be cool
+		// if this was selectable
+		let (rshift, gshift, bshift) = match leftover {
+			0 => (shift, shift, shift),
+			1 => (shift, shift - 1, shift),
+			2 => (shift - 1, shift - 1, shift),
+			_ => unreachable!(),
+		};
 
 		image
 			.0
 			.iter()
 			.map(|color| {
 				RGB8::new(
-					color.r >> shift << shift,
-					color.g >> shift << shift,
-					color.b >> shift << shift,
+					color.r >> rshift << rshift,
+					color.g >> gshift << gshift,
+					color.b >> bshift << bshift,
 				)
 			})
 			.collect::<HashSet<_>>()