// Copyright 2022 Google Inc. All Rights Reserved.

//

// Use of this source code is governed by a BSD-style license

// that can be found in the COPYING file in the root of the source

// tree. An additional intellectual property rights grant can be found

// in the file PATENTS. All contributing project authors may

// be found in the AUTHORS file in the root of the source tree.

// -----------------------------------------------------------------------------

//

// Colorspace utilities.

#include "sharpyuv/sharpyuv_csp.h"

#include <assert.h>

#include <math.h>

#include <stddef.h>

static int ToFixed16(float f) { return (int)floor(f * (1 << 16) + 0.5f); }

void SharpYuvComputeConversionMatrix(const SharpYuvColorSpace* yuv_color_space,

                                     SharpYuvConversionMatrix* matrix) {

  const float kr = yuv_color_space->kr;

  const float kb = yuv_color_space->kb;

  const float kg = 1.0f - kr - kb;

  const float cb = 0.5f / (1.0f - kb);

  const float cr = 0.5f / (1.0f - kr);

  const int shift = yuv_color_space->bit_depth - 8;

  const float denom = (float)((1 << yuv_color_space->bit_depth) - 1);

  float scale_y = 1.0f;

  float add_y = 0.0f;

  float scale_u = cb;

  float scale_v = cr;

  float add_uv = (float)(128 << shift);

  assert(yuv_color_space->bit_depth >= 8);

  if (yuv_color_space->range == kSharpYuvRangeLimited) {

    scale_y *= (219 << shift) / denom;

    scale_u *= (224 << shift) / denom;

    scale_v *= (224 << shift) / denom;

    add_y = (float)(16 << shift);

  }

  matrix->rgb_to_y[0] = ToFixed16(kr * scale_y);

  matrix->rgb_to_y[1] = ToFixed16(kg * scale_y);

  matrix->rgb_to_y[2] = ToFixed16(kb * scale_y);

  matrix->rgb_to_y[3] = ToFixed16(add_y);

  matrix->rgb_to_u[0] = ToFixed16(-kr * scale_u);

  matrix->rgb_to_u[1] = ToFixed16(-kg * scale_u);

  matrix->rgb_to_u[2] = ToFixed16((1 - kb) * scale_u);

  matrix->rgb_to_u[3] = ToFixed16(add_uv);

  matrix->rgb_to_v[0] = ToFixed16((1 - kr) * scale_v);

  matrix->rgb_to_v[1] = ToFixed16(-kg * scale_v);

  matrix->rgb_to_v[2] = ToFixed16(-kb * scale_v);

  matrix->rgb_to_v[3] = ToFixed16(add_uv);

}

// Matrices are in YUV_FIX fixed point precision.

// WebP's matrix, similar but not identical to kRec601LimitedMatrix

// Derived using the following formulas:

// Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16

// U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128

// V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128

static const SharpYuvConversionMatrix kWebpMatrix = {

  {16839, 33059, 6420, 16 << 16},

  {-9719, -19081, 28800, 128 << 16},

  {28800, -24116, -4684, 128 << 16},

};

// Kr=0.2990f Kb=0.1140f bit_depth=8 range=kSharpYuvRangeLimited

static const SharpYuvConversionMatrix kRec601LimitedMatrix = {

  {16829, 33039, 6416, 16 << 16},

  {-9714, -19071, 28784, 128 << 16},

  {28784, -24103, -4681, 128 << 16},

};

// Kr=0.2990f Kb=0.1140f bit_depth=8 range=kSharpYuvRangeFull

static const SharpYuvConversionMatrix kRec601FullMatrix = {

  {19595, 38470, 7471, 0},

  {-11058, -21710, 32768, 128 << 16},

  {32768, -27439, -5329, 128 << 16},

};

// Kr=0.2126f Kb=0.0722f bit_depth=8 range=kSharpYuvRangeLimited

static const SharpYuvConversionMatrix kRec709LimitedMatrix = {

  {11966, 40254, 4064, 16 << 16},

  {-6596, -22189, 28784, 128 << 16},

  {28784, -26145, -2639, 128 << 16},

};

// Kr=0.2126f Kb=0.0722f bit_depth=8 range=kSharpYuvRangeFull

static const SharpYuvConversionMatrix kRec709FullMatrix = {

  {13933, 46871, 4732, 0},

  {-7509, -25259, 32768, 128 << 16},

  {32768, -29763, -3005, 128 << 16},

};

const SharpYuvConversionMatrix* SharpYuvGetConversionMatrix(

    SharpYuvMatrixType matrix_type) {

  switch (matrix_type) {

    case kSharpYuvMatrixWebp:

      return &kWebpMatrix;

    case kSharpYuvMatrixRec601Limited:

      return &kRec601LimitedMatrix;

    case kSharpYuvMatrixRec601Full:

      return &kRec601FullMatrix;

    case kSharpYuvMatrixRec709Limited:

      return &kRec709LimitedMatrix;

    case kSharpYuvMatrixRec709Full:

      return &kRec709FullMatrix;

    case kSharpYuvMatrixNum:

      return NULL;

  }

  return NULL;

}