add alpha/requireAlpha argument when decoding images

remove size checks from setImage (we are assuming the caller knows the correct size)
This also adds some monkey-patch methods to js_interop to convert Float32List to a UInt8List (but use this with care, because it will only work for emscripten-allocated objects)

thermion_dart/lib/src/filament/src/implementation/ffi_filament_app.dart

@@ -310,6 +310,7 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
       TextureSamplerType textureSamplerType = TextureSamplerType.SAMPLER_2D,
       TextureFormat textureFormat = TextureFormat.RGBA16F,
       int? importedTextureHandle}) async {
+    
     var bitmask = flags.fold(0, (a, b) => a | b.value);
 
     final texturePtr = await withPointerCallback<TTexture>((cb) {
@@ -362,19 +363,28 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
     return FFITextureSampler(samplerPtr);
   }
 
+  /// Decodes the image data into a native LinearImage (floating point).
+  /// If [requireAlpha] is true, the decoded image will always contain an 
+  /// alpha channel (even if the original image did not contain one). 
   ///
-  ///
-  ///
-  Future<LinearImage> decodeImage(Uint8List data) async {
-    final name = "image";
+  Future<LinearImage> decodeImage(Uint8List data, { String name = "image", bool requireAlpha = false}) async {
+    
     late Pointer stackPtr;
     if (FILAMENT_WASM) {
       //stackPtr = stackSave();
     }
+    var now = DateTime.now();
+
     var ptr = Image_decode(
       data.address,
       data.length,
       name.toNativeUtf8().cast<Char>(),
+      requireAlpha
+    );
+
+    var finished = DateTime.now();
+    print(
+      "Image_decode (render thread) finished in ${finished.millisecondsSinceEpoch - now.millisecondsSinceEpoch}ms",
     );
 
     if (FILAMENT_WASM) {
@@ -1114,11 +1124,11 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
     if (FILAMENT_WASM) {
       stackPtr = stackSave();
     }
-    TransformManager_setTransform(transformManager, entity, matrix4ToDouble4x4(transform));
+    TransformManager_setTransform(
+        transformManager, entity, matrix4ToDouble4x4(transform));
     if (FILAMENT_WASM) {
       stackRestore(stackPtr);
     }
-    
   }
 
   ///
@@ -1129,7 +1139,7 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
     if (FILAMENT_WASM) {
       stackPtr = stackSave();
     }
-    
+
     var transform = double4x4ToMatrix4(
         TransformManager_getWorldTransform(transformManager, entity));
     if (FILAMENT_WASM) {
@@ -1137,5 +1147,4 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
     }
     return transform;
   }
-
 }

thermion_dart/lib/src/filament/src/implementation/ffi_texture.dart

@@ -165,15 +165,10 @@ class FFILinearImage extends LinearImage {
   }
 
   static Future<FFILinearImage> decode(Uint8List data,
-      [String name = "image"]) async {
-    final namePtr = name.toNativeUtf8();
-
-    final imagePtr = await withPointerCallback<TLinearImage>((cb) {
-      Image_decodeRenderThread(
-          data.address, data.lengthInBytes, namePtr.cast(), cb);
-    });
-
-    return FFILinearImage(imagePtr);
+      {String name = "image", bool requireAlpha = false}) async {
+    final image = await FilamentApp.instance!
+        .decodeImage(data, name: name, requireAlpha: requireAlpha);
+    return image as FFILinearImage;
   }
 
   Future<void> destroy() async {

thermion_dart/lib/src/filament/src/interface/filament_app.dart

@@ -133,7 +133,7 @@ abstract class FilamentApp<T> {
   ///
   /// Decodes the specified image data.
   ///
-  Future<LinearImage> decodeImage(Uint8List data);
+  Future<LinearImage> decodeImage(Uint8List data, { String name = "image", bool requireAlpha = false});
 
   ///
   /// Creates an (empty) imge with the given dimensions.

thermion_dart/lib/src/filament/src/interface/texture.dart

@@ -484,11 +484,17 @@ abstract class LinearImage {
   Future<int> getHeight();
   Future<int> getChannels();
   
+  /// Decodes the image contained in [data] and returns a texture of 
+  /// the corresponding size with the image set as mip-level 0. 
   ///
   ///
-  ///
-  static Future<Texture> decodeToTexture(Uint8List data, { TextureFormat textureFormat = TextureFormat.RGB32F, PixelDataFormat pixelDataFormat = PixelDataFormat.RGB, PixelDataType pixelDataType = PixelDataType.FLOAT, int levels = 1}) async {
-    final decodedImage = await FilamentApp.instance!.decodeImage(data);
+  static Future<Texture> decodeToTexture(Uint8List data, { 
+    TextureFormat textureFormat = TextureFormat.RGB32F,
+    PixelDataFormat pixelDataFormat = PixelDataFormat.RGB,
+    PixelDataType pixelDataType = PixelDataType.FLOAT,
+    int levels = 1, 
+    bool requireAlpha = false}) async {
+    final decodedImage = await FilamentApp.instance!.decodeImage(data, requireAlpha: requireAlpha);
     
     final texture = await FilamentApp.instance!.createTexture(
       await decodedImage.getWidth(),