feat: add image-resizer servlet

servlets/image-resizer/.cargo/config.toml

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+[build]
+target = "wasm32-wasip1"

servlets/image-resizer/.gitignore

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+# Generated by Cargo
+# will have compiled files and executables
+debug/
+target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+
+# RustRover
+#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
+#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
+#  and can be added to the global gitignore or merged into this file.  For a more nuclear
+#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
+#.idea/

servlets/image-resizer/Cargo.toml

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+[package]
+name = "image-resizer"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+name = "plugin"
+crate-type = ["cdylib"]
+
+[dependencies]
+extism-pdk = "1.1.0"
+chrono = { version = "0.4", features = ["serde"] }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+base64-serde = "0.7"
+base64 = "0.21"
+image = "0.25.5"
+
+[workspace]

servlets/image-resizer/prepare.sh

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+#!/bin/bash
+
+# Function to check if a command exists
+command_exists () {
+  command -v "$1" >/dev/null 2>&1
+}
+
+missing_deps=0
+
+# Check for Cargo
+if ! (command_exists cargo); then
+  missing_deps=1
+  echo "❌ Cargo/rust is not installed."
+  echo ""
+  echo "To install Rust, visit the official download page:"
+  echo "👉 https://www.rust-lang.org/tools/install"
+  echo ""
+  echo "Or install it using a package manager:"
+  echo ""
+  echo "🔹 macOS (Homebrew):"
+  echo "    brew install cargo"
+  echo ""
+  echo "🔹 Ubuntu/Debian:"
+  echo "    sudo apt-get install -y cargo"
+  echo ""
+  echo "🔹 Arch Linux:"
+  echo "    sudo pacman -S rust"
+  echo ""
+fi
+
+if ! (command_exists rustup); then
+  missing_deps=1
+  echo "❌ rustup is missing. Check your rust installation."
+  echo ""
+fi
+
+# Exit with a bad exit code if any dependencies are missing
+if [ "$missing_deps" -ne 0 ]; then
+  echo "Install the missing dependencies and ensure they are on your path. Then run this command again."
+  # TODO: remove sleep when cli bug is fixed
+  sleep 2
+  exit 1
+fi
+
+if ! (rustup target list --installed | grep -q '^wasm32-wasip1$'); then
+  if ! (rustup target add wasm32-wasip1); then
+    echo "❌ error encountered while adding target \"wasm32-wasip1\""
+    echo ""
+    echo "Update rustup with:"
+    echo "👉 rustup update"
+    echo ""
+    exit 1
+  fi
+fi
+
+if ! (rustup target list --installed | grep -q '^wasm32-unknown-unknown$'); then
+  rustup target add wasm32-unknown-unknown
+fi

servlets/image-resizer/src/lib.rs

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+mod pdk;
+
+use crate::types::ListToolsResult;
+use crate::types::ToolDescription;
+use base64::{
+    engine::general_purpose::STANDARD, engine::general_purpose::URL_SAFE_NO_PAD, Engine as _,
+};
+use extism_pdk::*;
+use image::GenericImageView;
+use image::ImageReader;
+use pdk::*;
+use serde_json::{Map, Value};
+use std::io::Cursor;
+
+// Called when the tool is invoked.
+// If you support multiple tools, you must switch on the input.params.name to detect which tool is being called.
+// The name will match one of the tool names returned from "describe".
+pub(crate) fn call(_input: types::CallToolRequest) -> Result<types::CallToolResult, Error> {
+    // load the params
+    let b64_image = _input
+        .params
+        .arguments
+        .as_ref()
+        .and_then(|args| args.get("data"))
+        .and_then(|data| data.as_str())
+        .ok_or_else(|| Error::msg("Argument `data` must be provided"))?;
+    let image_data = match URL_SAFE_NO_PAD.decode(b64_image) {
+        Ok(data) => data,
+        _ => STANDARD.decode(b64_image)?
+    };
+    let image = ImageReader::new(Cursor::new(image_data))
+        .with_guessed_format()?
+        .decode()?;
+    let scale = _input
+        .params
+        .arguments
+        .as_ref()
+        .and_then(|args| args.get("scale"))
+        .and_then(|scale| scale.as_number())
+        .ok_or_else(|| Error::msg("Argument `scale` must be provided"))?;
+    let scale = scale.as_f64().unwrap();
+
+    // scale
+    let (oldw, oldh) = image.dimensions();
+    let neww = ((oldw as f64) * scale) as u32;
+    let newh = ((oldh as f64) * scale) as u32;
+    let image = image.resize(neww, newh, image::imageops::FilterType::Nearest);
+
+    // return the result
+    let mut result_bytes: Vec<u8> = Vec::new();
+    image.write_to(&mut Cursor::new(&mut result_bytes), image::ImageFormat::Png)?;
+    let result_text = URL_SAFE_NO_PAD.encode(result_bytes.clone());
+    let result_image = STANDARD.encode(result_bytes);
+    Ok(types::CallToolResult {
+        content: vec![
+            types::Content {
+                r#type: types::ContentType::Image,
+                text: None,
+                annotations: None,
+                data: Some(result_image),
+                mime_type: Some("image/png".into()),
+            },
+            types::Content {
+                r#type: types::ContentType::Text,
+                text: Some(result_text),
+                annotations: None,
+                data: None,
+                mime_type: None,
+            },
+        ],
+        is_error: None,
+    })
+}
+
+// Called by mcpx to understand how and why to use this tool.
+// Note: Your servlet configs will not be set when this function is called,
+// so do not rely on config in this function
+pub(crate) fn describe() -> Result<types::ListToolsResult, Error> {
+    let mut data_prop: Map<String, Value> = Map::new();
+    data_prop.insert("type".into(), "string".into());
+    data_prop.insert(
+        "description".into(),
+        "base64url data of image file to resize".into(),
+    );
+
+    let mut scale_prop: Map<String, Value> = Map::new();
+    scale_prop.insert("type".into(), "number".into());
+    scale_prop.insert(
+        "description".into(),
+        "Amount to scale image, for example, 1 to keep the same, 2 to double the size, etc".into(),
+    );
+
+    let mut props: Map<String, Value> = Map::new();
+    props.insert("data".into(), data_prop.into());
+    props.insert("scale".into(), scale_prop.into());
+
+    let mut schema: Map<String, Value> = Map::new();
+    schema.insert("type".into(), "object".into());
+    schema.insert("properties".into(), Value::Object(props));
+    schema.insert(
+        "required".into(),
+        Value::Array(vec!["data".into(), "scale".into()]),
+    );
+
+    Ok(ListToolsResult {
+        tools: vec![ToolDescription {
+            name: "image-resizer".into(),
+            description: "Resize an image file".into(),
+            input_schema: schema,
+        }],
+    })
+}