Add MemoizeImpure node and cache image base64 in graph (#1595)

* Cache base64 representation of images when converting to graphic group

* Fix build

* Fix build again

* Actually fix it this time

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

node-graph/gcore/src/graphic_element.rs

@@ -159,7 +159,19 @@ async fn construct_artboard<Fut: Future<Output = GraphicGroup>>(
 }
 
 impl From<ImageFrame<Color>> for GraphicElement {
-	fn from(image_frame: ImageFrame<Color>) -> Self {
+	fn from(mut image_frame: ImageFrame<Color>) -> Self {
+		use base64::Engine;
+
+		let image = &image_frame.image;
+		if !image.data.is_empty() {
+			let output = image.to_png();
+			let preamble = "data:image/png;base64,";
+			let mut base64_string = String::with_capacity(preamble.len() + output.len() * 4);
+			base64_string.push_str(preamble);
+			base64::engine::general_purpose::STANDARD.encode_string(output, &mut base64_string);
+			image_frame.image.base64_string = Some(base64_string);
+		}
+
 		GraphicElement::ImageFrame(image_frame)
 	}
 }