that works

Cargo.toml

@@ -7,9 +7,11 @@ version = "0.0.0"
 crate-type = ["cdylib"]
 
 [dependencies]
+lodepng = "3.10.4"
 # Default enable napi4 feature, see https://nodejs.org/api/n-api.html#node-api-version-matrix
 napi = { version = "2.12.2", default-features = false, features = ["napi4"] }
 napi-derive = "2.12.2"
+sha2 = "0.10.8"
 
 [build-dependencies]
 napi-build = "2.0.1"

index.d.ts

@@ -4,3 +4,9 @@
 /* auto-generated by NAPI-RS */
 
 export declare function sum(a: number, b: number): number
+export declare function encodeImage(rawData: Uint8Array): ImageWithHashes
+export declare class ImageWithHashes {
+  png: Uint8Array
+  minecraftHash: Uint8Array
+  hash: Uint8Array
+}

index.js

@@ -310,6 +310,8 @@ if (!nativeBinding) {
   throw new Error(`Failed to load native binding`)
 }
 
-const { sum } = nativeBinding
+const { sum, ImageWithHashes, encodeImage } = nativeBinding
 
 module.exports.sum = sum
+module.exports.ImageWithHashes = ImageWithHashes
+module.exports.encodeImage = encodeImage

src/lib.rs

@@ -1,9 +1,62 @@
 #![deny(clippy::all)]
 
+use lodepng::FilterStrategy;
+use sha2::{Digest, Sha256};
+use napi::{
+    bindgen_prelude::{Buffer, ClassInstance, ObjectFinalize, This, Uint8Array, Unknown},
+    Env, Property, Result,
+};
+use napi_derive::napi;
+
 #[macro_use]
 extern crate napi_derive;
 
+pub const SKIN_WIDTH: u8 = 64;
+pub const SKIN_HEIGHT: u8 = 64;
+pub const SKIN_CHANNELS: u8 = 4;
+
 #[napi]
 pub fn sum(a: i32, b: i32) -> i32 {
   a + b
 }
+
+#[napi]
+pub struct ImageWithHashes {
+    pub png: Uint8Array,
+    pub minecraft_hash: Uint8Array,
+    pub hash: Uint8Array,
+}
+
+#[napi]
+pub fn encode_image(raw_data: &[u8]) -> ImageWithHashes {
+    encode_custom_image(raw_data, SKIN_WIDTH, SKIN_HEIGHT)
+}
+
+//#[napi]
+pub fn encode_custom_image(raw_data: &[u8], width: u8, height: u8) -> ImageWithHashes {
+    // encode images like Minecraft does
+    let mut encoder = lodepng::Encoder::new();
+    encoder.set_auto_convert(false);
+    encoder.info_png_mut().interlace_method = 0; // should be 0 but just to be sure
+
+    let mut encoder_settings = encoder.settings_mut();
+    encoder_settings.zlibsettings.set_level(4);
+    encoder_settings.filter_strategy = FilterStrategy::ZERO;
+
+    let png = encoder.encode(raw_data, width as usize, height as usize).unwrap();
+
+    let mut hasher = Sha256::new();
+
+    hasher.update(&png);
+    let minecraft_hash = hasher.finalize_reset();
+
+    // make our own hash
+    hasher.update(raw_data);
+    let hash = hasher.finalize();
+
+    ImageWithHashes {
+        png: Uint8Array::from(png.as_slice()),
+        minecraft_hash: Uint8Array::from(minecraft_hash.as_slice()),
+        hash: Uint8Array::from(hash.as_slice()),
+    }
+}