// 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_CHROMA_FROM_LUMA_H_

#define LIB_JXL_CHROMA_FROM_LUMA_H_

// Chroma-from-luma, computed using heuristics to determine the best linear

// model for the X and B channels from the Y channel.

#include <jxl/memory_manager.h>

#include <cstddef>

#include <cstdint>

#include "lib/jxl/base/status.h"

#include "lib/jxl/cms/opsin_params.h"

#include "lib/jxl/dec_bit_reader.h"

#include "lib/jxl/field_encodings.h"

#include "lib/jxl/frame_dimensions.h"

#include "lib/jxl/image.h"

namespace jxl {

// Tile is the rectangular grid of blocks that share color correlation

// parameters ("factor_x/b" such that residual_b = blue - Y * factor_b).

static constexpr size_t kColorTileDim = 64;

static_assert(kColorTileDim % kBlockDim == 0,

              "Color tile dim should be divisible by block dim");

static constexpr size_t kColorTileDimInBlocks = kColorTileDim / kBlockDim;

static_assert(kGroupDimInBlocks % kColorTileDimInBlocks == 0,

              "Group dim should be divisible by color tile dim");

static constexpr uint8_t kDefaultColorFactor = 84;

// JPEG DCT coefficients are at most 1024. CfL constants are at most 127, and

// the ratio of two entries in a JPEG quantization table is at most 255. Thus,

// since the CfL denominator is 84, this leaves 12 bits of mantissa to be used.

// For extra caution, we use 11.

static constexpr uint8_t kCFLFixedPointPrecision = 11;

static constexpr U32Enc kColorFactorDist(Val(kDefaultColorFactor), Val(256),

                                         BitsOffset(8, 2), BitsOffset(16, 258));

struct ColorCorrelation {

  float YtoXRatio(int32_t x_factor) const {

    return base_correlation_x_ + x_factor * color_scale_;

  }

  float YtoBRatio(int32_t b_factor) const {

    return base_correlation_b_ + b_factor * color_scale_;

  }

  Status DecodeDC(BitReader* br);

  // We consider a CfL map to be JPEG-reconstruction-compatible if base

  // correlation is 0, no DC correlation is used, and we use the default color

  // factor.

  bool IsJPEGCompatible() const {

    return base_correlation_x_ == 0 && base_correlation_b_ == 0 &&

           ytob_dc_ == 0 && ytox_dc_ == 0 &&

           color_factor_ == kDefaultColorFactor;

  }

  static int32_t RatioJPEG(int32_t factor) {

    return factor * (1 << kCFLFixedPointPrecision) / kDefaultColorFactor;

  }

  void SetColorFactor(uint32_t factor) {

    color_factor_ = factor;

    color_scale_ = 1.0f / color_factor_;

    RecomputeDCFactors();

  }

  void SetYToBDC(int32_t ytob_dc) {

    ytob_dc_ = ytob_dc;

    RecomputeDCFactors();

  }

  void SetYToXDC(int32_t ytox_dc) {

    ytox_dc_ = ytox_dc;

    RecomputeDCFactors();

  }

  int32_t GetYToXDC() const { return ytox_dc_; }

  int32_t GetYToBDC() const { return ytob_dc_; }

  float GetColorFactor() const { return color_factor_; }

  float GetBaseCorrelationX() const { return base_correlation_x_; }

  float GetBaseCorrelationB() const { return base_correlation_b_; }

  const float* DCFactors() const { return dc_factors_; }

  void RecomputeDCFactors() {

    dc_factors_[0] = YtoXRatio(ytox_dc_);

    dc_factors_[2] = YtoBRatio(ytob_dc_);

  }

 private:

  friend struct ColorCorrelationMap;

  float dc_factors_[4] = {};

  // range of factor: -1.51 to +1.52

  uint32_t color_factor_ = kDefaultColorFactor;

  float color_scale_ = 1.0f / color_factor_;

  float base_correlation_x_ = 0.0f;

  float base_correlation_b_ = jxl::cms::kYToBRatio;

  int32_t ytox_dc_ = 0;

  int32_t ytob_dc_ = 0;

};

struct ColorCorrelationMap {

  ColorCorrelationMap() = default;

  // Copy disallowed.

  ColorCorrelationMap(const ColorCorrelationMap&) = delete;

  ColorCorrelationMap& operator=(const ColorCorrelationMap&) = delete;

  // Move default.

  ColorCorrelationMap(ColorCorrelationMap&&) = default;

  ColorCorrelationMap& operator=(ColorCorrelationMap&&) = default;

  // xsize/ysize are in pixels

  // set XYB=false to do something close to no-op cmap (needed for now since

  // cmap is mandatory)

  static StatusOr<ColorCorrelationMap> Create(JxlMemoryManager* memory_manager,

                                              size_t xsize, size_t ysize,

                                              bool XYB = true);

  const ColorCorrelation& base() const { return base_; }

  Status DecodeDC(BitReader* br) { return base_.DecodeDC(br); }

  ImageSB ytox_map;

  ImageSB ytob_map;

 private:

  ColorCorrelation base_;

};

}  // namespace jxl

#endif  // LIB_JXL_CHROMA_FROM_LUMA_H_