Dither images to correct width

showbits-typst-plugin/src/lib.rs

@@ -1,18 +1,57 @@
 use std::io::Cursor;
 
-use image::ImageFormat;
+use image::{
+    ImageFormat,
+    imageops::{self, FilterType},
+};
 use mark::dither::{AlgoFloydSteinberg, Algorithm, DiffEuclid, Palette};
 use palette::LinSrgb;
 use wasm_minimal_protocol::{initiate_protocol, wasm_func};
 
 initiate_protocol!();
 
+fn i64_from_bytes(bytes: &[u8]) -> Result<i64, String> {
+    let bytes: [u8; 8] = bytes.try_into().map_err(|it| format!("{it}"))?;
+    Ok(i64::from_le_bytes(bytes))
+}
+
+fn size_from_i64(size: i64) -> Result<Option<u32>, String> {
+    if size < 0 {
+        return Ok(None); // Unlimited width
+    }
+
+    let size: u32 = size.try_into().map_err(|_| "size too large")?;
+    Ok(Some(size))
+}
+
 #[wasm_func]
-pub fn dither(image: &[u8]) -> Result<Vec<u8>, String> {
-    let image = image::load_from_memory(image)
+pub fn dither(image: &[u8], max_width: &[u8], max_height: &[u8]) -> Result<Vec<u8>, String> {
+    let max_width = size_from_i64(i64_from_bytes(max_width)?)?;
+    let max_height = size_from_i64(i64_from_bytes(max_height)?)?;
+
+    let mut image = image::load_from_memory(image)
         .map_err(|it| format!("Failed to read image: {it:?}"))?
         .to_rgba8();
 
+    let image_width = image.width();
+    let image_height = image.height();
+
+    let scale_factor = match (max_width, max_height) {
+        (None, None) => 1.0,
+        (None, Some(height)) => height as f32 / image_height as f32,
+        (Some(width), None) => width as f32 / image_width as f32,
+        (Some(width), Some(height)) => {
+            (width as f32 / image_width as f32).min(height as f32 / image_height as f32)
+        }
+    };
+
+    let target_width = (image_width as f32 * scale_factor) as u32;
+    let target_height = (image_height as f32 * scale_factor) as u32;
+
+    if image_width != target_width || image_height != target_height {
+        image = imageops::resize(&image, target_width, target_height, FilterType::CatmullRom);
+    }
+
     let palette = Palette::new(vec![
         LinSrgb::new(0.0, 0.0, 0.0),
         LinSrgb::new(1.0, 1.0, 1.0),
@@ -27,3 +66,16 @@ pub fn dither(image: &[u8]) -> Result<Vec<u8>, String> {
 
     Ok(bytes)
 }
+
+#[wasm_func]
+pub fn debug(value: &[u8]) -> Result<Vec<u8>, String> {
+    // let value: [u8; 4] = value
+    //     .try_into()
+    //     .map_err(|it| format!("incorrect number of bytes: {it}"))?;
+
+    // let be = u32::from_be_bytes(value);
+    // let le = u32::from_le_bytes(value);
+
+    // Ok(format!("be: {be}, le: {le}").into_bytes())
+    Ok(format!("{value:?}").into_bytes())
+}