// 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, &params));

  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