Improve the Vibrance node (#1050)

* Fix vibrance

* Improve results

* Clean up implementation

* Fix warnings from unrelated commit

* Improve negative vibrance

editor/src/messages/tool/tool_messages/path_tool.rs

@@ -6,9 +6,7 @@ use crate::messages::prelude::*;
 use crate::messages::tool::common_functionality::overlay_renderer::OverlayRenderer;
 use crate::messages::tool::common_functionality::shape_editor::{ManipulatorPointInfo, ShapeEditor};
 use crate::messages::tool::common_functionality::snapping::SnapManager;
-use crate::messages::tool::common_functionality::transformation_cage::axis_align_drag;
-use crate::messages::tool::utility_types::{EventToMessageMap, Fsm, ToolActionHandlerData, ToolMetadata, ToolTransition, ToolType};
-use crate::messages::tool::utility_types::{HintData, HintGroup, HintInfo};
+use crate::messages::tool::utility_types::{EventToMessageMap, Fsm, HintData, HintGroup, HintInfo, ToolActionHandlerData, ToolMetadata, ToolTransition, ToolType};
 
 use document_legacy::intersection::Quad;
 use graphene_std::vector::consts::ManipulatorType;

node-graph/gcore/src/raster/adjustments.rs

@@ -216,13 +216,61 @@ pub struct VibranceNode<Vibrance> {
 	vibrance: Vibrance,
 }
 
-// TODO: The current results are incorrect, try implementing this from https://stackoverflow.com/questions/33966121/what-is-the-algorithm-for-vibrance-filters
+// From https://stackoverflow.com/questions/33966121/what-is-the-algorithm-for-vibrance-filters
+// The results of this implementation are very close to correct, but not quite perfect
 #[node_macro::node_fn(VibranceNode)]
 fn vibrance_node(color: Color, vibrance: f64) -> Color {
-	let [hue, saturation, lightness, alpha] = color.to_hsla();
+	// TODO: Remove conversion to linear when the whole node graph uses linear color
+	let color = color.to_linear_srgb();
+
 	let vibrance = vibrance as f32 / 100.;
-	let saturation = saturation + vibrance * (1. - saturation);
-	Color::from_hsla(hue, saturation, lightness, alpha)
+	// Slow the effect down by half when it's negative, since artifacts begin appearing past -50%.
+	// So this scales the 0% to -50% range to 0% to -100%.
+	let slowed_vibrance = if vibrance >= 0. { vibrance } else { vibrance * 0.5 };
+
+	let channel_max = color.r().max(color.g()).max(color.b());
+	let channel_min = color.r().min(color.g()).min(color.b());
+	let channel_difference = channel_max - channel_min;
+
+	let scale_multiplier = if channel_max == color.r() {
+		let green_blue_difference = (color.g() - color.b()).abs();
+		let t = (green_blue_difference / channel_difference).min(1.);
+		t * 0.5 + 0.5
+	} else {
+		1.
+	};
+	let scale = slowed_vibrance * scale_multiplier * (2. - channel_difference);
+	let channel_reduction = channel_min * scale;
+	let scale = 1. + scale * (1. - channel_difference);
+
+	let luminance_initial = color.to_linear_srgb().luminance_srgb();
+	let altered_color = color.map_rgb(|channel| (channel * scale - channel_reduction)).to_linear_srgb();
+	let luminance = altered_color.luminance_srgb();
+	let altered_color = altered_color.map_rgb(|channel| channel * luminance_initial / luminance);
+
+	let channel_max = altered_color.r().max(altered_color.g()).max(altered_color.b());
+	let altered_color = if Color::linear_to_srgb(channel_max) > 1. {
+		let scale = (1. - luminance) / (channel_max - luminance);
+		altered_color.map_rgb(|channel| (channel - luminance) * scale + luminance)
+	} else {
+		altered_color
+	};
+	let altered_color = altered_color.to_gamma_srgb();
+
+	let altered_color = if vibrance >= 0. {
+		altered_color
+	} else {
+		// TODO: The result ends up a bit darker than it should be, further investigation is needed
+		let luminance = color.luminance_rec_601();
+
+		// Near -0% vibrance we mostly use `altered_color`.
+		// Near -100% vibrance, we mostly use half the desaturated luminance color and half `altered_color`.
+		let factor = -slowed_vibrance;
+		altered_color.map_rgb(|channel| channel * (1. - factor) + luminance * factor)
+	};
+
+	// TODO: Remove conversion to linear when the whole node graph uses linear color
+	altered_color.to_gamma_srgb()
 }
 
 #[derive(Debug, Clone, Copy)]

node-graph/gcore/src/raster/color.rs

@@ -235,7 +235,7 @@ impl Color {
 	}
 
 	pub fn with_luminance(&self, luminance: f32) -> Color {
-		let d = luminance - self.luminance_rec_601();
+		let d = luminance - self.luminance_rec_601_rounded();
 		self.map_rgb(|c| (c + d).clamp(0., 1.))
 	}