Add the Mask node (#1080)

* Add MaskImageNode

Co-authored-by: Dennis Kobert <dennis@kobert.dev>

node-graph/gstd/src/executor.rs

@@ -44,7 +44,7 @@ fn map_gpu_single_image(input: Image, node: String) -> Image {
 		nodes: [(
 			0,
 			DocumentNode {
-				name: "Image filter Node".into(),
+				name: "Image Filter".into(),
 				inputs: vec![NodeInput::Network(concrete!(Color))],
 				implementation: DocumentNodeImplementation::Unresolved(identifier),
 				metadata: DocumentNodeMetadata::default(),

node-graph/gstd/src/raster.rs

@@ -194,6 +194,40 @@ fn compute_transformed_bounding_box(transform: DAffine2) -> Bbox {
 	}
 }
 
+#[derive(Debug, Clone, Copy)]
+pub struct MaskImageNode<Mask> {
+	mask: Mask,
+}
+
+#[node_macro::node_fn(MaskImageNode)]
+fn mask_image(mut image: ImageFrame, mask: ImageFrame) -> ImageFrame {
+	let image_size = DVec2::new(image.image.width as f64, image.image.height as f64);
+	let mask_size = DVec2::new(mask.image.width as f64, mask.image.height as f64);
+
+	if mask_size == DVec2::ZERO {
+		return image;
+	}
+
+	// Transforms a point from the background image to the forground image
+	let bg_to_fg = DAffine2::from_scale(mask_size) * mask.transform.inverse() * image.transform * DAffine2::from_scale(1. / image_size);
+
+	for y in 0..image.image.height {
+		for x in 0..image.image.width {
+			let image_point = DVec2::new(x as f64, y as f64);
+			let mut mask_point = bg_to_fg.transform_point2(image_point);
+			mask_point = mask_point.clamp(DVec2::ZERO, mask_size);
+
+			let image_pixel = image.get_mut(x as usize, y as usize);
+			let mask_pixel = mask.sample(mask_point);
+			let alpha = image_pixel.a() * mask_pixel.r();
+
+			*image_pixel = Color::from_rgbaf32(image_pixel.r(), image_pixel.g(), image_pixel.b(), alpha).unwrap();
+		}
+	}
+
+	image
+}
+
 #[derive(Debug, Clone, Copy)]
 pub struct BlendImageNode<Background, MapFn> {
 	background: Background,