Rasterize node: the rasterized image is leaking from one document to another

[rvliq]

Description:
When using the Rasterize node in multiple documents which are opened at the same time, a rasterized image produced by the Rasterize node in one document is shown in another document which also uses the Rasterize node.

Environment:
The bug is happening in the web version of Graphite (link https://dev.graphite.art, commit 4ab75c9) opened in the Opera web browser (v125.0.5729.49) on MS Windows 11 Home (v10.0.26200).

Steps to reproduce:

1. Open the web version of Graphite at https://dev.graphite.art.
2. Create a new document.
3. In the document, draw a circle in the top-left corner of the document.
4. In the Properties panel, add the Rasterize node to the circle.
5. Create another document.
6. In that new document, draw a rectangle in the top-left corner of the document.
7. In the Properties panel, add the Rasterize node to the rectangle.

Expected: the rectangle is shown in the second document.
Actual: the circle from the first document is shown in the second document, instead of the rectangle.

[Ayush2k02]

Can I take this one !?

[Keavon]

Yes @Ayush2k02. See also https://discord.com/channels/731730685944922173/1134981447539761273/1454200983402975424 for the discussion, which includes a video, that will give you further details that you should be sure to reproduce before attempting.

[0HyperCube]

In my testing, the issue only occurs in SVG rendering mode and is due to the two images hashing to the same thing (since they are both almost completely white and the same size).

Specifically removing this condition from node-graph/libraries/rendering/src/renderer.rs:1254 (so that the code always runs) fixes the issue for me.

Graphite/node-graph/libraries/rendering/src/renderer.rs

Lines 1254 to 1258 in fa45efa

	if !render.image_data.iter().any(|(old_id, _)| *old_id == id) {
	let mut image = image.data().clone();
	image.map_pixels(|p| p.to_unassociated_alpha());
	render.image_data.push((id, image));
	}

The hashing code for images is included below:

Graphite/node-graph/libraries/raster-types/src/image.rs

Lines 104 to 116 in fa45efa

	// TODO: Evaluate if this will be a problem for our use case.
	/// Warning: This is an approximation of a hash, and is not guaranteed to not collide.
	impl<P: Hash + Pixel> Hash for Image<P> {
	fn hash<H: Hasher>(&self, state: &mut H) {
	const HASH_SAMPLES: u64 = 1000;
	let data_length = self.data.len() as u64;
	self.width.hash(state);
	self.height.hash(state);
	for i in 0..HASH_SAMPLES.min(data_length) {
	self.data[(i * data_length / HASH_SAMPLES) as usize].hash(state);
	}
	}
	}

Since the image is 1000x1000 and only contains a couple of pixels of black (from the thin strokes), the hash nearly always collides. You will see if you modify the stroke of one of the layers, the rasterised version will not update.

[Ayush2k02]

yeah, this was happening for me as well