Added noise stage.

jxl/src/features/mod.rs

@@ -3,4 +3,5 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+pub mod noise;
 pub mod spline;

jxl/src/features/noise.rs

@@ -0,0 +1,40 @@
+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+use crate::{bit_reader::BitReader, error::Result};
+#[derive(Debug, PartialEq, Default)]
+pub struct Noise {
+    pub lut: [f32; 8],
+}
+
+impl Noise {
+    pub fn read(br: &mut BitReader) -> Result<Noise> {
+        let mut noise = Noise::default();
+        for l in &mut noise.lut {
+            *l = (br.read(10)? as f32) / ((1 << 10) as f32);
+        }
+        Ok(noise)
+    }
+    pub fn strength(&self, vx: f32) -> f32 {
+        let k_scale = (self.lut.len() - 2) as f32;
+        let scaled_vx = f32::max(0.0, vx * k_scale);
+        let pre_floor_x = scaled_vx.floor();
+        let pre_frac_x = scaled_vx - pre_floor_x;
+        let floor_x = if scaled_vx >= k_scale + 1.0 {
+            k_scale
+        } else {
+            pre_floor_x
+        };
+        let frac_x = if scaled_vx >= k_scale + 1.0 {
+            1.0
+        } else {
+            pre_frac_x
+        };
+        let floor_x_int = floor_x as usize;
+        let low = self.lut[floor_x_int];
+        let hi = self.lut[floor_x_int + 1];
+        ((hi - low) * frac_x + low).clamp(0.0, 1.0)
+    }
+}

jxl/src/frame.rs

@@ -6,7 +6,7 @@
 use crate::{
     bit_reader::BitReader,
     error::Result,
-    features::spline::Splines,
+    features::{noise::Noise, spline::Splines},
     headers::{
         color_encoding::ColorSpace,
         encodings::UnconditionalCoder,
@@ -35,7 +35,7 @@ pub struct LfGlobalState {
     // TODO(veluca93): patches
     // TODO(veluca93): splines
     splines: Option<Splines>,
-    // TODO(veluca93): noise
+    noise: Option<Noise>,
     lf_quant: LfQuantFactors,
     // TODO(veluca93), VarDCT: HF quant matrices
     // TODO(veluca93), VarDCT: block context map
@@ -145,10 +145,12 @@ impl Frame {
             None
         };
 
-        if self.header.has_noise() {
+        let noise = if self.header.has_noise() {
             info!("decoding noise");
-            todo!("noise not implemented");
-        }
+            Some(Noise::read(br)?)
+        } else {
+            None
+        };
 
         let lf_quant = LfQuantFactors::new(br)?;
         debug!(?lf_quant);
@@ -180,6 +182,7 @@ impl Frame {
 
         self.lf_global = Some(LfGlobalState {
             splines,
+            noise,
             lf_quant,
             tree,
             modular_global,
@@ -197,6 +200,7 @@ mod test_frame {
         error::Error,
         features::spline::Point,
         headers::{FileHeader, JxlHeader},
+        util::test::assert_almost_eq,
     };
 
     use super::Frame;
@@ -262,4 +266,18 @@ mod test_frame {
         assert_eq!(spline.sigma_dct, EXPECTED_SIGMA_DCT);
         Ok(())
     }
+
+    #[test]
+    fn noise() -> Result<(), Error> {
+        let frame = read_frame(include_bytes!("../resources/test/8x8_noise.jxl"))?;
+        let lf_global = frame.lf_global.unwrap();
+        let noise = lf_global.noise.unwrap();
+        let want_noise = [
+            0.000000, 0.000977, 0.002930, 0.003906, 0.005859, 0.006836, 0.008789, 0.010742,
+        ];
+        for (index, noise_param) in want_noise.iter().enumerate() {
+            assert_almost_eq!(noise.lut[index], *noise_param, 1e-6);
+        }
+        Ok(())
+    }
 }

jxl/src/image.rs

@@ -184,6 +184,16 @@ impl<T: ImageDataType> Image<T> {
         Ok(img)
     }
 
+    #[cfg(test)]
+    pub fn new_range(size: (usize, usize), start: f32, step: f32) -> Result<Image<T>> {
+        let mut img = Self::new(size)?;
+        img.data
+            .iter_mut()
+            .enumerate()
+            .for_each(|(index, x)| *x = T::from_f64((start + step * index as f32) as f64));
+        Ok(img)
+    }
+
     #[cfg(test)]
     pub fn new_constant(size: (usize, usize), val: T) -> Result<Image<T>> {
         let mut img = Self::new(size)?;

jxl/src/render/stages/mod.rs

@@ -6,6 +6,7 @@
 mod chroma_upsample;
 mod convert;
 mod nearest_neighbor;
+mod noise;
 mod save;
 mod upsample;