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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.
#include "lib/jxl/quantizer.h"
#include <algorithm>
#include <cstring>
#include "lib/jxl/base/compiler_specific.h"
#include "lib/jxl/base/rect.h"
#include "lib/jxl/field_encodings.h"
#include "lib/jxl/fields.h"
#include "lib/jxl/image.h"
#include "lib/jxl/image_ops.h"
#include "lib/jxl/quant_weights.h"
namespace jxl {
static const int32_t kDefaultQuant = 64;
#if JXL_CXX_LANG < JXL_CXX_17
constexpr int32_t Quantizer::kQuantMax;
#endif
Quantizer::Quantizer(const DequantMatrices& dequant)
: Quantizer(dequant, kDefaultQuant, kGlobalScaleDenom / kDefaultQuant) {}
Quantizer::Quantizer(const DequantMatrices& dequant, int quant_dc,
int global_scale)
: global_scale_(global_scale), quant_dc_(quant_dc), dequant_(&dequant) {
RecomputeFromGlobalScale();
inv_quant_dc_ = inv_global_scale_ / quant_dc_;
memcpy(zero_bias_, kZeroBiasDefault, sizeof(kZeroBiasDefault));
}
void Quantizer::ComputeGlobalScaleAndQuant(float quant_dc, float quant_median,
float quant_median_absd) {
// Target value for the median value in the quant field.
const float kQuantFieldTarget = 5;
// We reduce the median of the quant field by the median absolute deviation:
// higher resolution on highly varying quant fields.
float scale = kGlobalScaleDenom * (quant_median - quant_median_absd) /
kQuantFieldTarget;
// Ensure that new_global_scale is positive and no more than 1<<15.
if (scale < 1) scale = 1;
if (scale > (1 << 15)) scale = 1 << 15;
int new_global_scale = static_cast<int>(scale);
// Ensure that quant_dc_ will always be at least
// 0.625 * kGlobalScaleDenom/kGlobalScaleNumerator = 10.
const int scaled_quant_dc =
static_cast<int>(quant_dc * kGlobalScaleNumerator * 1.6);
if (new_global_scale > scaled_quant_dc) {
new_global_scale = scaled_quant_dc;
if (new_global_scale <= 0) new_global_scale = 1;
}
global_scale_ = new_global_scale;
// Code below uses inv_global_scale_.
RecomputeFromGlobalScale();
float fval = quant_dc * inv_global_scale_ + 0.5f;
fval = std::min<float>(1 << 16, fval);
const int new_quant_dc = static_cast<int>(fval);
quant_dc_ = new_quant_dc;
// quant_dc_ was updated, recompute values.
RecomputeFromGlobalScale();
}
void Quantizer::SetQuantFieldRect(const ImageF& qf, const Rect& rect,
ImageI* JXL_RESTRICT raw_quant_field) const {
for (size_t y = 0; y < rect.ysize(); ++y) {
const float* JXL_RESTRICT row_qf = rect.ConstRow(qf, y);
int32_t* JXL_RESTRICT row_qi = rect.Row(raw_quant_field, y);
for (size_t x = 0; x < rect.xsize(); ++x) {
int val = ClampVal(row_qf[x] * inv_global_scale_ + 0.5f);
row_qi[x] = val;
}
}
}
Status Quantizer::SetQuantField(const float quant_dc, const ImageF& qf,
ImageI* JXL_RESTRICT raw_quant_field) {
std::vector<float> data(qf.xsize() * qf.ysize());
for (size_t y = 0; y < qf.ysize(); ++y) {
const float* JXL_RESTRICT row_qf = qf.Row(y);
for (size_t x = 0; x < qf.xsize(); ++x) {
float quant = row_qf[x];
data[qf.xsize() * y + x] = quant;
}
}
std::nth_element(data.begin(), data.begin() + data.size() / 2, data.end());
const float quant_median = data[data.size() / 2];
std::vector<float> deviations(data.size());
for (size_t i = 0; i < data.size(); i++) {
deviations[i] = fabsf(data[i] - quant_median);
}
std::nth_element(deviations.begin(),
deviations.begin() + deviations.size() / 2,
deviations.end());
const float quant_median_absd = deviations[deviations.size() / 2];
ComputeGlobalScaleAndQuant(quant_dc, quant_median, quant_median_absd);
if (raw_quant_field) {
JXL_ENSURE(SameSize(*raw_quant_field, qf));
SetQuantFieldRect(qf, Rect(qf), raw_quant_field);
}
return true;
}
void Quantizer::SetQuant(float quant_dc, float quant_ac,
ImageI* JXL_RESTRICT raw_quant_field) {
ComputeGlobalScaleAndQuant(quant_dc, quant_ac, 0);
int32_t val = ClampVal(quant_ac * inv_global_scale_ + 0.5f);
FillImage(val, raw_quant_field);
}
Status QuantizerParams::VisitFields(Visitor* JXL_RESTRICT visitor) {
JXL_QUIET_RETURN_IF_ERROR(visitor->U32(
BitsOffset(11, 1), BitsOffset(11, 2049), BitsOffset(12, 4097),
BitsOffset(16, 8193), 1, &global_scale));
JXL_QUIET_RETURN_IF_ERROR(visitor->U32(Val(16), BitsOffset(5, 1),
BitsOffset(8, 1), BitsOffset(16, 1), 1,
&quant_dc));
return true;
}
QuantizerParams Quantizer::GetParams() const {
QuantizerParams params;
params.global_scale = global_scale_;
params.quant_dc = quant_dc_;
return params;
}
Status Quantizer::Decode(BitReader* reader) {
QuantizerParams params;
JXL_RETURN_IF_ERROR(Bundle::Read(reader, ¶ms));
global_scale_ = static_cast<int>(params.global_scale);
quant_dc_ = static_cast<int>(params.quant_dc);
RecomputeFromGlobalScale();
return true;
}
void Quantizer::DumpQuantizationMap(const ImageI& raw_quant_field) const {
printf("Global scale: %d (%.7f)\nDC quant: %d\n", global_scale_,
global_scale_ * 1.0 / kGlobalScaleDenom, quant_dc_);
printf("AC quantization Map:\n");
for (size_t y = 0; y < raw_quant_field.ysize(); ++y) {
for (size_t x = 0; x < raw_quant_field.xsize(); ++x) {
printf(" %3d", raw_quant_field.Row(y)[x]);
}
printf("\n");
}
}
} // namespace jxl