Dither images using wasm plugin

showbits-thermal-printer/src/documents/image/lib.typ

@@ -0,0 +1 @@
+../lib.typ

showbits-thermal-printer/src/documents/image/main.typ

@@ -0,0 +1,4 @@
+#import "lib.typ";
+#show: it => lib.init(it)
+
+#lib.dither("image.png")

showbits-thermal-printer/src/documents/image/mod.rs

@@ -0,0 +1,24 @@
+use std::io::Cursor;
+
+use anyhow::Context;
+use image::{ImageFormat, RgbaImage};
+use showbits_typst::Typst;
+
+pub struct Image {
+    pub image: RgbaImage,
+}
+
+impl Image {
+    pub fn into_typst(self) -> anyhow::Result<Typst> {
+        let mut bytes: Vec<u8> = Vec::new();
+        self.image
+            .write_to(&mut Cursor::new(&mut bytes), ImageFormat::Png)
+            .context("failed to encode image as png")?;
+
+        let typst = super::typst_with_lib()
+            .with_file("/image.png", bytes)
+            .with_main_file(include_str!("main.typ"));
+
+        Ok(typst)
+    }
+}

showbits-thermal-printer/src/documents/image/plugin.wasm

@@ -0,0 +1 @@
+../plugin.wasm

showbits-thermal-printer/src/documents/lib.typ

@@ -20,4 +20,14 @@
 // the same size after tearing off the paper.
 #let feed = v(64pt + 32pt)
 
-#import plugin("plugin.wasm") as plugin
+////////////
+// Plugin //
+////////////
+
+#import plugin("plugin.wasm") as p
+
+#let dither(path) = {
+  let bytes = read(path, encoding: none)
+  let dithered = p.dither(bytes)
+  image(dithered)
+}