Support remote image URLs in Typst compiler

README.md

@@ -65,6 +65,12 @@ Uploaded images can be referenced natively using the `#image` function in Typst.
 #image("logo.png", width: 50%)
 ```
 
+You can also reference remote images directly by their `http://` or `https://` URL — TypstDrive fetches them at compile time.
+
+```typst
+#image("https://example.com/logo.png", width: 50%)
+```
+
 ## Self-Hosting
 
 TypstDrive is completely self-hostable. A Docker image packages both the Rust backend and the SvelteKit frontend into a single container.

server/Cargo.toml

@@ -37,3 +37,4 @@ tempfile = "3.27.0"
 sha2 = "0.10"
 base64 = "0.22"
 toml = "0.8"
+ureq = "2.12"

server/src/world.rs

@@ -1,5 +1,6 @@
 use chrono::Datelike;
 use std::collections::HashMap;
+use std::io::Read;
 
 use typst::diag::{FileError, FileResult};
 use typst::foundations::{Bytes, Datetime, Duration};
@@ -22,10 +23,44 @@ pub struct MemoryWorld {
 
 const LOCAL_NAMESPACE: &str = "typstdrive";
 
+const REMOTE_FETCH_TIMEOUT_SECS: u64 = 15;
+const REMOTE_MAX_BYTES: u64 = 50 * 1024 * 1024;
+
 fn normalize_path(path: &str) -> String {
     path.trim_start_matches('/').replace('\\', "/")
 }
 
+fn remote_url(path: &str) -> Option<String> {
+    for scheme in ["https", "http"] {
+        let prefix = format!("{scheme}:/");
+        if let Some(rest) = path.strip_prefix(&prefix) {
+            let host_and_path = rest.trim_start_matches('/');
+            return Some(format!("{scheme}://{host_and_path}"));
+        }
+    }
+    None
+}
+
+fn fetch_remote(url: &str) -> FileResult<Vec<u8>> {
+    let agent = ureq::AgentBuilder::new()
+        .timeout(std::time::Duration::from_secs(REMOTE_FETCH_TIMEOUT_SECS))
+        .build();
+
+    let response = agent
+        .get(url)
+        .call()
+        .map_err(|e| FileError::Other(Some(format!("failed to fetch {url}: {e}").into())))?;
+
+    let mut bytes = Vec::new();
+    response
+        .into_reader()
+        .take(REMOTE_MAX_BYTES)
+        .read_to_end(&mut bytes)
+        .map_err(|e| FileError::Other(Some(format!("failed to read {url}: {e}").into())))?;
+
+    Ok(bytes)
+}
+
 impl MemoryWorld {
     pub fn new_project(
         entrypoint: String,
@@ -103,6 +138,10 @@ impl MemoryWorld {
             return root.load(id.vpath()).map(|bytes| bytes.to_vec());
         }
 
+        if let Some(url) = remote_url(&path) {
+            return fetch_remote(&url);
+        }
+
         self.files
             .get(&path)
             .cloned()