Add speckle noise

src/noise.rs

@@ -33,6 +33,59 @@ where
     }
 }
 
+/// Adds multiplicative speckle noise to an image with the given mean and standard deviation.
+/// Noise can be added independently per channel for data augmentation, or just per pixel for
+/// realistic sensor noise simulation.
+pub fn speckle_noise<P>(
+    image: &Image<P>,
+    per_channel: bool,
+    mean: f64,
+    stddev: f64,
+    seed: u64,
+) -> Image<P>
+where
+    P: Pixel,
+    P::Subpixel: Into<f64> + Clamp<f64>,
+{
+    let mut out = image.clone();
+    speckle_noise_mut(&mut out, per_channel, mean, stddev, seed);
+    out
+}
+#[doc=generate_mut_doc_comment!("speckle_noise")]
+pub fn speckle_noise_mut<P>(
+    image: &mut Image<P>,
+    per_channel: bool,
+    mean: f64,
+    stddev: f64,
+    seed: u64,
+) where
+    P: Pixel,
+    P::Subpixel: Into<f64> + Clamp<f64>,
+{
+    let mut rng: StdRng = SeedableRng::seed_from_u64(seed);
+    let normal = Normal::new(mean, stddev).unwrap();
+
+    if per_channel {
+        // Add sampled noise per channel in each pixel
+        for p in image.pixels_mut() {
+            p.apply(|c| {
+                let noise = normal.sample(&mut rng);
+                let original = c.into();
+                P::Subpixel::clamp(original + original * noise)
+            });
+        }
+    } else {
+        // Use the same noise pattern for each channel
+        for p in image.pixels_mut() {
+            let noise = normal.sample(&mut rng);
+            p.apply(|c| {
+                let original = c.into();
+                P::Subpixel::clamp(original + original * noise)
+            });
+        }
+    }
+}
+
 /// Converts pixels to black or white at the given `rate` (between 0.0 and 1.0).
 /// Black and white occur with equal probability.
 pub fn salt_and_pepper_noise<P>(image: &Image<P>, rate: f64, seed: u64) -> Image<P>
@@ -84,4 +137,13 @@ mod benches {
         });
         black_box(image);
     }
+
+    #[bench]
+    fn bench_speckle_noise_mut(b: &mut Bencher) {
+        let mut image = GrayImage::new(100, 100);
+        b.iter(|| {
+            speckle_noise_mut(&mut image, true, 0.0, 0.4, 1);
+        });
+        black_box(image);
+    }
 }