Add per-channel parameters to the 'Levels' node and make its midtones a gamma value (#4535)

* Add per-channel records and a gamma midtones value to the 'Levels' node, with a channel selector in its Properties panel

* Migrate the old 'Levels' midtones through its output range and bound a lone midtone marker by the track edges

editor/src/messages/layout/utility_types/widgets/input_widgets.rs

@@ -695,11 +695,9 @@ pub struct SpectrumInput {
 #[cfg_attr(feature = "wasm", derive(tsify::Tsify))]
 #[derive(Clone, Debug, Default, PartialEq, serde::Serialize, serde::Deserialize)]
 pub struct SpectrumMarker {
-	/// Position of the marker along the spectrum track, normally from 0 to 1. A shifted or stretched non-cyclic ramp can
-	/// place it outside that range, where the track draws only the markers falling within its visible span.
+	/// Position along the track, normally 0..1. A shifted or stretched non-cyclic ramp can push it outside, where it is not drawn.
 	position: f64,
-	/// Position (0..1) of the midpoint between this marker and the next, used only if `show_midpoints` is true.
-	/// The last marker's value controls the wrapped interval when `track_cyclic` is set, and is otherwise ignored.
+	/// Midpoint (0..1) of the interval to the next marker, used only with `show_midpoints`. The last marker's midpoint spans the wrap of a cyclic track, or is otherwise ignored.
 	midpoint: f64,
 	/// CSS color string for the marker handle's fill. Set via `SpectrumMarker::new` from a linear [`Color`],
 	/// discarding any transparency so the handle always shows the RGB that steers the interpolation.
@@ -708,6 +706,9 @@ pub struct SpectrumMarker {
 	/// Whether a dashed line runs from this marker to the next through the lane below the track. Dragging it carries both markers.
 	#[serde(rename = "dashedToNext")]
 	dashed_to_next: bool,
+	/// Whether this marker follows its neighbors instead of bounding them, so they may drag past its drawn position.
+	#[serde(rename = "betweenNeighbors")]
+	between_neighbors: bool,
 }
 
 impl SpectrumMarker {
@@ -718,9 +719,15 @@ impl SpectrumMarker {
 			midpoint,
 			handle_color_css,
 			dashed_to_next: false,
+			between_neighbors: false,
 		}
 	}
 
+	pub fn between_neighbors(mut self) -> Self {
+		self.between_neighbors = true;
+		self
+	}
+
 	pub fn dash_to_next(mut self) -> Self {
 		self.dashed_to_next = true;
 		self

editor/src/messages/portfolio/document/node_graph/node_properties.rs

@@ -1399,17 +1399,63 @@ pub(crate) fn transfer_curves_properties(node_id: NodeId, context: &mut NodeProp
 pub(crate) fn levels_properties(node_id: NodeId, context: &mut NodePropertiesContext) -> Vec<LayoutGroup> {
 	use graphene_std::raster::levels::*;
 
+	let mut channel_info = ParameterWidgetsInfo::new(node_id, ChannelInput, true, context);
+	channel_info.exposable = false;
+	let channel = enum_choice::<AdjustmentChannel>().for_socket(channel_info).property_row();
+
+	let channel_value = match get_document_node(node_id, context).ok().and_then(|document_node| document_node.input_value(ChannelInput).cloned()) {
+		Some(TaggedValue::AdjustmentChannel(channel)) => channel,
+		_ => AdjustmentChannel::Rgb,
+	};
+	let [shadows, midtones, highlights, output_minimums, output_maximums]: [ParameterRef; 5] = match channel_value {
+		AdjustmentChannel::Rgb => [
+			ShadowsInput.into(),
+			MidtonesInput.into(),
+			HighlightsInput.into(),
+			OutputMinimumsInput.into(),
+			OutputMaximumsInput.into(),
+		],
+		AdjustmentChannel::Red => [
+			RedShadowsInput.into(),
+			RedMidtonesInput.into(),
+			RedHighlightsInput.into(),
+			RedOutputMinimumsInput.into(),
+			RedOutputMaximumsInput.into(),
+		],
+		AdjustmentChannel::Green => [
+			GreenShadowsInput.into(),
+			GreenMidtonesInput.into(),
+			GreenHighlightsInput.into(),
+			GreenOutputMinimumsInput.into(),
+			GreenOutputMaximumsInput.into(),
+		],
+		AdjustmentChannel::Blue => [
+			BlueShadowsInput.into(),
+			BlueMidtonesInput.into(),
+			BlueHighlightsInput.into(),
+			BlueOutputMinimumsInput.into(),
+			BlueOutputMaximumsInput.into(),
+		],
+		AdjustmentChannel::Alpha => [
+			AlphaShadowsInput.into(),
+			AlphaMidtonesInput.into(),
+			AlphaHighlightsInput.into(),
+			AlphaOutputMinimumsInput.into(),
+			AlphaOutputMaximumsInput.into(),
+		],
+	};
+
 	let input_range_params = [
-		SpectrumSectionParam::new(ShadowsInput, Color::BLACK, 0., MarkerScale::Percent),
-		SpectrumSectionParam::new(MidtonesInput, Color::MIDDLE_GRAY, 50., MarkerScale::Percent),
-		SpectrumSectionParam::new(HighlightsInput, Color::WHITE, 100., MarkerScale::Percent),
+		SpectrumSectionParam::new(shadows, Color::BLACK, 0., MarkerScale::Percent),
+		SpectrumSectionParam::new(midtones, Color::MIDDLE_GRAY, 1., MarkerScale::Gamma).between_neighbors(),
+		SpectrumSectionParam::new(highlights, Color::WHITE, 100., MarkerScale::Percent),
 	];
 	let output_range_params = [
-		SpectrumSectionParam::new(OutputMinimumsInput, Color::BLACK, 0., MarkerScale::Percent),
-		SpectrumSectionParam::new(OutputMaximumsInput, Color::WHITE, 100., MarkerScale::Percent),
+		SpectrumSectionParam::new(output_minimums, Color::BLACK, 0., MarkerScale::Percent),
+		SpectrumSectionParam::new(output_maximums, Color::WHITE, 100., MarkerScale::Percent),
 	];
 
-	let mut layout = Vec::with_capacity(5);
+	let mut layout = vec![channel];
 	build_shared_spectrum_section(node_id, context, &bw_track(), &input_range_params, &mut layout);
 	build_shared_spectrum_section(node_id, context, &bw_track(), &output_range_params, &mut layout);
 	layout
@@ -1459,6 +1505,8 @@ struct SpectrumSectionParam {
 	scale: MarkerScale,
 	/// Whether a dashed line joins the marker to the next parameter's marker.
 	dash_to_next: bool,
+	/// Whether the marker takes its scale position within the span between its neighbors rather than the whole track, following them as they move.
+	between_neighbors: bool,
 }
 
 impl SpectrumSectionParam {
@@ -1469,9 +1517,15 @@ impl SpectrumSectionParam {
 			default_value,
 			scale,
 			dash_to_next: false,
+			between_neighbors: false,
 		}
 	}
 
+	fn between_neighbors(mut self) -> Self {
+		self.between_neighbors = true;
+		self
+	}
+
 	fn dash_to_next(mut self) -> Self {
 		self.dash_to_next = true;
 		self
@@ -1507,6 +1561,7 @@ fn build_shared_spectrum_section(node_id: NodeId, context: &mut NodePropertiesCo
 	let mut marker_default_positions = Vec::new();
 	let mut marker_scales = Vec::new();
 	let mut marker_positions = Vec::new();
+	let mut marker_between = Vec::new();
 	let mut marker_colors_and_links = Vec::new();
 	for (i, param) in params.iter().enumerate() {
 		let (exposed, value) = exposure_and_value[i];
@@ -1518,20 +1573,41 @@ fn build_shared_spectrum_section(node_id: NodeId, context: &mut NodePropertiesCo
 		marker_input_indices.push(param.parameter.input_index);
 		marker_default_positions.push(param.scale.position(param.default_value));
 		marker_scales.push(param.scale);
+		marker_between.push(param.between_neighbors);
 		marker_colors_and_links.push((param.handle_color, param.dash_to_next && next_has_marker));
 	}
 
-	// Enforce non-decreasing order so markers never visually cross, matching the node's algorithm where shadows takes precedence
-	for i in 1..marker_positions.len() {
-		marker_positions[i] = marker_positions[i].max(marker_positions[i - 1]);
+	// Enforce non-decreasing order so markers never visually cross, matching the node's algorithm where shadows takes precedence.
+	// A marker placed between its neighbors bounds nothing here and instead takes its scale position within their settled span.
+	let mut floor = 0.;
+	for (position, &between) in marker_positions.iter_mut().zip(&marker_between) {
+		if between {
+			continue;
+		}
+		*position = position.max(floor);
+		floor = *position;
+	}
+	for i in 0..marker_positions.len() {
+		if marker_between[i] {
+			let left = if i == 0 { 0. } else { marker_positions[i - 1] };
+			let right = marker_positions.get(i + 1).copied().unwrap_or(1.);
+			marker_positions[i] = left + marker_positions[i] * (right - left);
+		}
 	}
 
 	let spectrum_markers: Vec<SpectrumMarker> = marker_positions
 		.iter()
 		.zip(&marker_colors_and_links)
-		.map(|(&position, &(handle_color, dashed))| {
-			let marker = SpectrumMarker::new(position, 0.5, handle_color);
-			if dashed { marker.dash_to_next() } else { marker }
+		.zip(&marker_between)
+		.map(|((&position, &(handle_color, dashed)), &between)| {
+			let mut marker = SpectrumMarker::new(position, 0.5, handle_color);
+			if dashed {
+				marker = marker.dash_to_next();
+			}
+			if between {
+				marker = marker.between_neighbors();
+			}
+			marker
 		})
 		.collect();
 
@@ -1550,21 +1626,35 @@ fn build_shared_spectrum_section(node_id: NodeId, context: &mut NodePropertiesCo
 				let marker_default_positions = marker_default_positions.clone();
 				let marker_scales = marker_scales.clone();
 				let marker_positions = marker_positions.clone();
+				let marker_between = marker_between.clone();
 				move |update: &SpectrumInputUpdate| {
 					let i = match update {
 						SpectrumInputUpdate::MoveMarker { index, .. } | SpectrumInputUpdate::ResetMarker { index } => *index as usize,
 						_ => return Message::NoOp,
 					};
-					let (Some(&input_index), Some(&scale), Some(&default_position)) = (marker_input_indices.get(i), marker_scales.get(i), marker_default_positions.get(i)) else {
+					let (Some(&input_index), Some(&scale), Some(&between), Some(&default_position)) =
+						(marker_input_indices.get(i), marker_scales.get(i), marker_between.get(i), marker_default_positions.get(i))
+					else {
 						return Message::NoOp;
 					};
-					let left = if i == 0 { 0. } else { marker_positions[i - 1] };
-					let right = marker_positions.get(i + 1).copied().unwrap_or(1.);
+
+					// The span the marker's scale maps onto: its neighbors' positions when placed between them, otherwise the track between the
+					// nearest markers that bound it, which a marker placed between its neighbors never does
+					let bounding = |j: usize| between || !marker_between[j];
+					let left = (0..i).rev().find(|&j| bounding(j)).map_or(0., |j| marker_positions[j]);
+					let right = (i + 1..marker_positions.len()).find(|&j| bounding(j)).map_or(1., |j| marker_positions[j]);
 
 					let scale_position = match update {
+						SpectrumInputUpdate::MoveMarker { position, .. } if between => {
+							let span = right - left;
+							if span <= f64::EPSILON {
+								return Message::NoOp;
+							}
+							((position - left) / span).clamp(0., 1.)
+						}
 						SpectrumInputUpdate::MoveMarker { position, .. } => *position,
 						// A default that would cross a neighbor falls back to the midpoint between them
-						SpectrumInputUpdate::ResetMarker { .. } if (left..=right).contains(&default_position) => default_position,
+						SpectrumInputUpdate::ResetMarker { .. } if between || (left..=right).contains(&default_position) => default_position,
 						SpectrumInputUpdate::ResetMarker { .. } => (left + right) / 2.,
 						_ => return Message::NoOp,
 					};

editor/src/messages/portfolio/document_migration.rs

@@ -2196,6 +2196,31 @@ fn migrate_node(node_id: &NodeId, node: &DocumentNode, network_path: &[NodeId],
 		inputs_count = 3;
 	}
 
+	// Levels' Midtones became the gamma value it encoded, and each channel gained its own record after the composite one
+	if reference == DefinitionIdentifier::ProtoNode(graphene_std::raster::levels::IDENTIFIER) && inputs_count == 6 {
+		let mut node_template = resolve_document_node_type(&reference)?.default_node_template();
+		document.network_interface.replace_implementation(node_id, network_path, &mut node_template);
+		let old_inputs = document.network_interface.replace_inputs(node_id, network_path, &mut node_template)?;
+		let output_level = |index: usize, default: f32| match old_inputs.get(index).and_then(|input| input.as_value()) {
+			Some(TaggedValue::F32(percent)) => percent / 100.,
+			_ => default,
+		};
+		let (output_minimums, output_maximums) = (output_level(4, 0.), output_level(5, 1.));
+		for (index, input) in old_inputs.iter().take(6).enumerate() {
+			let input = match (index, input.as_value()) {
+				(2, Some(TaggedValue::F32(percent))) => {
+					// The old node's midtones-to-gamma mapping, from https://stackoverflow.com/questions/39510072/algorithm-for-adjustment-of-image-levels
+					let midtones = output_minimums + (output_maximums - output_minimums) * percent / 100.;
+					let gamma = if midtones < 0.5 { 1. + 9. * (1. - midtones * 2.) } else { ((1. - midtones) * 2.).max(0.01) };
+					NodeInput::value(TaggedValue::F32(gamma.clamp(0.01, 9.99)), input.is_exposed())
+				}
+				_ => input.clone(),
+			};
+			document.network_interface.set_input(&InputConnector::node_at_index(*node_id, index), input, network_path);
+		}
+		inputs_count = 27;
+	}
+
 	if reference == DefinitionIdentifier::ProtoNode(graphene_std::repeat::repeat_on_points::IDENTIFIER) && inputs_count == 2 {
 		let mut node_template = resolve_document_node_type(&reference)?.default_node_template();
 		document.network_interface.replace_implementation(node_id, network_path, &mut node_template);