From b2728da81069c05ad24c6728c38375b87da4754b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philipp=20Do=CC=88rfler?= <phdoerfler@gmail.com>
Date: Thu, 21 Jan 2016 19:41:31 +0100
Subject: [PATCH] Added primitive sobel convolution.

---
 src/conv.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/conv.rs b/src/conv.rs
index 61e41ec..19649da 100644
--- a/src/conv.rs
+++ b/src/conv.rs
@@ -94,12 +94,32 @@ fn gaussian_kernel(w: usize, sigma: f32) -> Vec<f32> {
     k
 }
 
+fn sobel_kernel(horizontal: bool) -> Vec<f32> {
+    let mut k = vec![0f32; 9];
+    if horizontal {
+        k[0] = -1.0; k[1] =  0.0; k[2] =  1.0;
+        k[3] = -2.0; k[4] =  0.0; k[5] =  2.0;
+        k[6] = -1.0; k[7] =  0.0; k[8] =  1.0;
+    } else {
+        k[0] = -1.0; k[1] = -2.0; k[2] = -1.0;
+        k[3] =  0.0; k[4] =  0.0; k[5] =  0.0;
+        k[6] =  1.0; k[7] =  2.0; k[8] =  1.0;
+    }
+    
+    k
+}
+
 pub fn gaussian_blur<T: Pixel>(src: &Image<T>, kernel_width :usize, sigma: f32) -> Image<T> {
     assert!(kernel_width >= 1);
     let k = gaussian_kernel(kernel_width, sigma);
     conv2d_sep(src, &k, &k)
 }
 
+pub fn sobel<T: Pixel>(src: &Image<T>, horizontal: bool) -> Image<T> {
+    let k = sobel_kernel(horizontal);
+    conv2d_sep(src, &k, &k)
+}
+
 #[cfg(test)]
 mod test {
     use std::path::Path;