New node: Blur (#2477)

* Implementation of gaussian blur and box blur with linear/nonlinear colorspace in raster category

* styling/formatting

* Partial code review

* remove image crate, use conversion functions from color.rs

* fix box blur checkmark, fix linear/gamma conversion

* mult/unmult alpha before/after blur

* Code review

---------

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

node-graph/gstd/src/filter.rs

@@ -0,0 +1,179 @@
+use graph_craft::proto::types::PixelLength;
+use graphene_core::raster::image::{Image, ImageFrameTable};
+use graphene_core::raster::{Bitmap, BitmapMut};
+use graphene_core::transform::{Transform, TransformMut};
+use graphene_core::{Color, Ctx};
+
+/// Blurs the image with a Gaussian or blur kernel filter.
+#[node_macro::node(category("Raster: Filter"))]
+async fn blur(
+	_: impl Ctx,
+	/// The image to be blurred.
+	image_frame: ImageFrameTable<Color>,
+	/// The radius of the blur kernel.
+	#[range((0., 100.))]
+	radius: PixelLength,
+	/// Use a lower-quality box kernel instead of a circular Gaussian kernel. This is faster but produces boxy artifacts.
+	box_blur: bool,
+	/// Opt to incorrectly apply the filter with color calculations in gamma space for compatibility with the results from other software.
+	gamma: bool,
+) -> ImageFrameTable<Color> {
+	let image_frame_transform = image_frame.transform();
+	let image_frame_alpha_blending = image_frame.one_instance_ref().alpha_blending;
+
+	let image = image_frame.one_instance_ref().instance.clone();
+
+	// Run blur algorithm
+	let blurred_image = if radius < 0.1 {
+		// Minimum blur radius
+		image.clone()
+	} else if box_blur {
+		box_blur_algorithm(image, radius, gamma)
+	} else {
+		gaussian_blur_algorithm(image, radius, gamma)
+	};
+
+	let mut result = ImageFrameTable::new(blurred_image);
+	*result.transform_mut() = image_frame_transform;
+	*result.one_instance_mut().alpha_blending = *image_frame_alpha_blending;
+
+	result
+}
+
+// 1D gaussian kernel
+fn gaussian_kernel(radius: f64) -> Vec<f64> {
+	// Given radius, compute the size of the kernel that's approximately three times the radius
+	let kernel_radius = (3. * radius).ceil() as usize;
+	let kernel_size = 2 * kernel_radius + 1;
+	let mut gaussian_kernel: Vec<f64> = vec![0.; kernel_size];
+
+	// Kernel values
+	let two_radius_squared = 2. * radius * radius;
+	let sum = gaussian_kernel
+		.iter_mut()
+		.enumerate()
+		.map(|(i, value_at_index)| {
+			let x = i as f64 - kernel_radius as f64;
+			let exponent = -(x * x) / two_radius_squared;
+			*value_at_index = exponent.exp();
+			*value_at_index
+		})
+		.sum::<f64>();
+
+	// Normalize
+	gaussian_kernel.iter_mut().for_each(|value_at_index| *value_at_index /= sum);
+
+	gaussian_kernel
+}
+
+fn gaussian_blur_algorithm(mut original_buffer: Image<Color>, radius: f64, gamma: bool) -> Image<Color> {
+	if gamma {
+		original_buffer.map_pixels(|px| px.to_gamma_srgb().to_associated_alpha(px.a()));
+	} else {
+		original_buffer.map_pixels(|px| px.to_associated_alpha(px.a()));
+	}
+
+	let (width, height) = original_buffer.dimensions();
+
+	// Create 1D gaussian kernel
+	let kernel = gaussian_kernel(radius);
+	let half_kernel = kernel.len() / 2;
+
+	// Intermediate buffer for horizontal and vertical passes
+	let mut x_axis = Image::new(width, height, Color::TRANSPARENT);
+	let mut y_axis = Image::new(width, height, Color::TRANSPARENT);
+
+	for pass in [false, true] {
+		let (max, old_buffer, current_buffer) = match pass {
+			false => (width, &original_buffer, &mut x_axis),
+			true => (height, &x_axis, &mut y_axis),
+		};
+		let pass = pass as usize;
+
+		for y in 0..height {
+			for x in 0..width {
+				let (mut r_sum, mut g_sum, mut b_sum, mut a_sum, mut weight_sum) = (0., 0., 0., 0., 0.);
+
+				for (i, &weight) in kernel.iter().enumerate() {
+					let p = [x, y][pass] as i32 + (i as i32 - half_kernel as i32);
+
+					if p >= 0 && p < max as i32 {
+						if let Some(px) = old_buffer.get_pixel([p as u32, x][pass], [y, p as u32][pass]) {
+							r_sum += px.r() as f64 * weight;
+							g_sum += px.g() as f64 * weight;
+							b_sum += px.b() as f64 * weight;
+							a_sum += px.a() as f64 * weight;
+							weight_sum += weight;
+						}
+					}
+				}
+
+				// Normalize
+				let (r, g, b, a) = if weight_sum > 0. {
+					((r_sum / weight_sum) as f32, (g_sum / weight_sum) as f32, (b_sum / weight_sum) as f32, (a_sum / weight_sum) as f32)
+				} else {
+					let px = old_buffer.get_pixel(x, y).unwrap();
+					(px.r(), px.g(), px.b(), px.a())
+				};
+				current_buffer.set_pixel(x, y, Color::from_rgbaf32_unchecked(r, g, b, a));
+			}
+		}
+	}
+
+	if gamma {
+		y_axis.map_pixels(|px| px.to_linear_srgb().to_unassociated_alpha());
+	} else {
+		y_axis.map_pixels(|px| px.to_unassociated_alpha());
+	}
+
+	y_axis
+}
+
+fn box_blur_algorithm(mut original_buffer: Image<Color>, radius: f64, gamma: bool) -> Image<Color> {
+	if gamma {
+		original_buffer.map_pixels(|px| px.to_gamma_srgb().to_associated_alpha(px.a()));
+	} else {
+		original_buffer.map_pixels(|px| px.to_associated_alpha(px.a()));
+	}
+
+	let (width, height) = original_buffer.dimensions();
+	let mut x_axis = Image::new(width, height, Color::TRANSPARENT);
+	let mut y_axis = Image::new(width, height, Color::TRANSPARENT);
+
+	for pass in [false, true] {
+		let (max, old_buffer, current_buffer) = match pass {
+			false => (width, &original_buffer, &mut x_axis),
+			true => (height, &x_axis, &mut y_axis),
+		};
+		let pass = pass as usize;
+
+		for y in 0..height {
+			for x in 0..width {
+				let (mut r_sum, mut g_sum, mut b_sum, mut a_sum, mut weight_sum) = (0., 0., 0., 0., 0.);
+
+				let i = [x, y][pass];
+				for d in (i as i32 - radius as i32).max(0)..=(i as i32 + radius as i32).min(max as i32 - 1) {
+					if let Some(px) = old_buffer.get_pixel([d as u32, x][pass], [y, d as u32][pass]) {
+						let weight = 1.;
+						r_sum += px.r() as f64 * weight;
+						g_sum += px.g() as f64 * weight;
+						b_sum += px.b() as f64 * weight;
+						a_sum += px.a() as f64 * weight;
+						weight_sum += weight;
+					}
+				}
+
+				let (r, g, b, a) = ((r_sum / weight_sum) as f32, (g_sum / weight_sum) as f32, (b_sum / weight_sum) as f32, (a_sum / weight_sum) as f32);
+				current_buffer.set_pixel(x, y, Color::from_rgbaf32_unchecked(r, g, b, a));
+			}
+		}
+	}
+
+	if gamma {
+		y_axis.map_pixels(|px| px.to_linear_srgb().to_unassociated_alpha());
+	} else {
+		y_axis.map_pixels(|px| px.to_unassociated_alpha());
+	}
+
+	y_axis
+}

node-graph/gstd/src/lib.rs

@@ -8,6 +8,7 @@ pub mod vector;
 pub use graphene_core::*;
 pub mod brush;
 pub mod dehaze;
+pub mod filter;
 pub mod image_color_palette;
 #[cfg(feature = "wasm")]
 pub mod wasm_application_io;