Implement sobel filter

src/filter.rs

@@ -0,0 +1,3 @@
+pub mod sobel;
+
+pub use sobel::sobel;

src/filter/sobel.rs

@@ -0,0 +1,55 @@
+use crate::image::*;
+use crate::kernel::Kernel;
+use crate::*;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Vector {
+    pub magnitude: f32,
+    pub direction: f32,
+}
+
+impl Default for Vector {
+    fn default() -> Self {
+        Vector {
+            magnitude: 0.0,
+            direction: 0.0,
+        }
+    }
+}
+
+const KERNEL_X: [[f32; 3]; 3] =
+    [[-1.0, 0.0, 1.0], [-2.0, 0.0, 2.0], [-1.0, 0.0, 1.0]];
+const KERNEL_Y: [[f32; 3]; 3] =
+    [[-1.0, -2.0, -1.0], [0.0, 0.0, 0.0], [1.0, 2.0, 1.0]];
+
+pub fn sobel(img: Image<Luminance>) -> Image<Vector> {
+    let x_edges = KERNEL_X.convolve(&img);
+    let y_edges = KERNEL_Y.convolve(&img);
+
+    let mut result = image::Image::<Vector>::with_extent(x_edges.extent);
+    result.for_each(|x, y, p| {
+		let gx = x_edges.at(x, y).y;
+		let gy = y_edges.at(x, y).y;
+        p.magnitude = norm(gx, gy);
+		p.direction = gy.atan2(gx);
+    });
+
+	normalise_magnitude(&mut result);
+	result
+}
+
+fn norm(x: f32, y: f32) -> f32 {
+    (x * x + y * y).sqrt()
+}
+
+fn normalise_magnitude(img: &mut Image<Vector>) {
+	let mut max = f32::NEG_INFINITY;
+	for p in &img.pixels {
+		if p.magnitude > max {
+			max = p.magnitude;
+		}
+	}
+	img.for_each(|_, _, p| {
+		p.magnitude /= max;
+	});
+}

src/lib.rs

@@ -1,2 +1,3 @@
 pub mod image;
 pub mod kernel;
+pub mod filter;