Dither images using wasm plugin

showbits-typst-plugin/Cargo.toml

@@ -6,9 +6,11 @@ edition = { workspace = true }
 [lib]
 crate-type = ["cdylib"]
 
-[dependencies.wasm-minimal-protocol]
-git = "https://github.com/astrale-sharp/wasm-minimal-protocol.git"
-rev = "90336ebf2d99844fd8f8e99ea7096af96526cbf4"
+[dependencies]
+image = { workspace = true, features = ["png"] }
+mark = { workspace = true }
+palette = { workspace = true }
+wasm-minimal-protocol = { workspace = true }
 
 [profile.release]
 lto = true        # Enable link-time optimization

showbits-typst-plugin/src/lib.rs

@@ -1,8 +1,29 @@
-use wasm_minimal_protocol::*;
+use std::io::Cursor;
+
+use image::ImageFormat;
+use mark::dither::{AlgoFloydSteinberg, Algorithm, DiffEuclid, Palette};
+use palette::LinSrgb;
+use wasm_minimal_protocol::{initiate_protocol, wasm_func};
 
 initiate_protocol!();
 
 #[wasm_func]
-pub fn debug_print(arg: &[u8]) -> Vec<u8> {
-    format!("{arg:?}").into_bytes()
+pub fn dither(image: &[u8]) -> Result<Vec<u8>, String> {
+    let image = image::load_from_memory(image)
+        .map_err(|it| format!("Failed to read image: {it:?}"))?
+        .to_rgba8();
+
+    let palette = Palette::new(vec![
+        LinSrgb::new(0.0, 0.0, 0.0),
+        LinSrgb::new(1.0, 1.0, 1.0),
+    ]);
+
+    let dithered = <AlgoFloydSteinberg as Algorithm<LinSrgb, DiffEuclid>>::run(image, &palette);
+
+    let mut bytes: Vec<u8> = Vec::new();
+    dithered
+        .write_to(&mut Cursor::new(&mut bytes), ImageFormat::Png)
+        .map_err(|it| format!("Failed to write image: {it:?}"))?;
+
+    Ok(bytes)
 }