Source code
Revision control
Copy as Markdown
Other Tools
// 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 <array>
#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;
using Lut = std::array<float, kNumNoisePoints>;
Lut lut;
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(user): instead of 1, this should be a proper Y range.
constexpr float kScale = kScaleNumerator / 1.0f;
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_