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diff --git a/third_party/jpeg-xl/lib/jxl/noise.h b/third_party/jpeg-xl/lib/jxl/noise.h
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+++ b/third_party/jpeg-xl/lib/jxl/noise.h
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+// 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.
+
+#ifndef LIB_JXL_NOISE_H_
+#define LIB_JXL_NOISE_H_
+
+// Noise parameters shared by encoder/decoder.
+
+#include <stddef.h>
+
+#include <algorithm>
+#include <cmath>
+#include <utility>
+
+#include "lib/jxl/base/compiler_specific.h"
+
+namespace jxl {
+
+const float kNoisePrecision = 1 << 10;
+
+struct NoiseParams {
+  // LUT index is an intensity of pixel / mean intensity of patch
+  static constexpr size_t kNumNoisePoints = 8;
+  float lut[kNumNoisePoints];
+
+  void Clear() {
+    for (float& i : lut) i = 0.f;
+  }
+  bool HasAny() const {
+    for (float i : lut) {
+      if (std::abs(i) > 1e-3f) return true;
+    }
+    return false;
+  }
+};
+
+static inline std::pair<int, float> IndexAndFrac(float x) {
+  constexpr size_t kScaleNumerator = NoiseParams::kNumNoisePoints - 2;
+  // TODO: instead of 1, this should be a proper Y range.
+  constexpr float kScale = kScaleNumerator / 1;
+  float scaled_x = std::max(0.f, x * kScale);
+  float floor_x;
+  float frac_x = std::modf(scaled_x, &floor_x);
+  if (JXL_UNLIKELY(scaled_x >= kScaleNumerator + 1)) {
+    floor_x = kScaleNumerator;
+    frac_x = 1.f;
+  }
+  return std::make_pair(static_cast<int>(floor_x), frac_x);
+}
+
+struct NoiseLevel {
+  float noise_level;
+  float intensity;
+};
+
+}  // namespace jxl
+
+#endif  // LIB_JXL_NOISE_H_