Extract graster-nodes (#2783)

node-graph/graster-nodes/src/generate_curves.rs

@@ -0,0 +1,46 @@
+//! requires bezier-rs
+
+use crate::curve::{Curve, CurveManipulatorGroup, ValueMapperNode};
+use bezier_rs::{Bezier, TValue};
+use graphene_core::color::{Channel, Linear};
+use graphene_core::context::Ctx;
+
+const WINDOW_SIZE: usize = 1024;
+
+#[node_macro::node(category(""))]
+fn generate_curves<C: Channel + Linear>(_: impl Ctx, curve: Curve, #[implementations(f32, f64)] _target_format: C) -> ValueMapperNode<C> {
+	let [mut pos, mut param]: [[f32; 2]; 2] = [[0.; 2], curve.first_handle];
+	let mut lut = vec![C::from_f64(0.); WINDOW_SIZE];
+	let end = CurveManipulatorGroup {
+		anchor: [1.; 2],
+		handles: [curve.last_handle, [0.; 2]],
+	};
+	for sample in curve.manipulator_groups.iter().chain(std::iter::once(&end)) {
+		let [x0, y0, x1, y1, x2, y2, x3, y3] = [pos[0], pos[1], param[0], param[1], sample.handles[0][0], sample.handles[0][1], sample.anchor[0], sample.anchor[1]].map(f64::from);
+
+		let bezier = Bezier::from_cubic_coordinates(x0, y0, x1, y1, x2, y2, x3, y3);
+
+		let [left, right] = [pos[0], sample.anchor[0]].map(|c| c.clamp(0., 1.));
+		let lut_index_left: usize = (left * (lut.len() - 1) as f32).floor() as _;
+		let lut_index_right: usize = (right * (lut.len() - 1) as f32).ceil() as _;
+		for index in lut_index_left..=lut_index_right {
+			let x = index as f64 / (lut.len() - 1) as f64;
+			let y = if x <= x0 {
+				y0
+			} else if x >= x3 {
+				y3
+			} else {
+				bezier.find_tvalues_for_x(x)
+					.next()
+					.map(|t| bezier.evaluate(TValue::Parametric(t.clamp(0., 1.))).y)
+					// Fall back to a very bad approximation if Bezier-rs fails
+					.unwrap_or_else(|| (x - x0) / (x3 - x0) * (y3 - y0) + y0)
+			};
+			lut[index] = C::from_f64(y);
+		}
+
+		pos = sample.anchor;
+		param = sample.handles[1];
+	}
+	ValueMapperNode::new(lut)
+}