#include "igs_density.h"

#include <iostream></iostream>

namespace {

float accum_by_trans_(const float src_value /* 元値(R,G,B) */

                      ,

                      const float transparent /* src_valueの透明度(0...1) */

                      ,

                      const int integer_part /* 濃度値の整数部分(0...) */

                      ,

                      const double fractional_part /* 濃度値の少数部分(0...1) */

) {

  float accumulation = src_value;

  if (1 <= integer_part) {

    for (int ii = 1; ii < integer_part; ++ii) {

      accumulation = accumulation * transparent + src_value;

    }

    if (0.f < fractional_part) {

      accumulation +=

          ((accumulation * transparent + src_value) - accumulation) *

          fractional_part;

    }

  } else { /* 整数部分がゼロ以下のとき */

    if (0.f < fractional_part) {

      accumulation *= fractional_part;

    } else { /* 少数部分もゼロ以下のとき */

      accumulation = 0.f;

    }

  }

  return (1.f < accumulation) ? 1.f

                              : ((accumulation < 0.f) ? 0.f : accumulation);

}

}  // namespace

#include <limits>           /* std::numeric_limits */</limits>

#include "igs_ifx_common.h" /* igs::image::rgba */

namespace {

void change_(float *image_array, const int height, const int width,

             const int channels, const float *ref, const double density) {

  const int integer_part       = (int)density;

  const double fractional_part = density - (int)density;

  using namespace igs::image::rgba;

  const int pixsize = height * width;

  for (int ii = 0; ii < pixsize; ++ii, image_array += channels) {

    const float rr1 = image_array[red];

    const float gg1 = image_array[gre];

    const float bb1 = image_array[blu];

    const float aa1 = image_array[alp];

    float rr2 = accum_by_trans_(rr1, 1.0 - aa1, integer_part, fractional_part);

    float gg2 = accum_by_trans_(gg1, 1.0 - aa1, integer_part, fractional_part);

    float bb2 = accum_by_trans_(bb1, 1.0 - aa1, integer_part, fractional_part);

    float aa2 = accum_by_trans_(aa1, 1.0 - aa1, integer_part, fractional_part);

    /* 参照画像あればピクセル単位の画像変化 */

    if (ref != nullptr) {

      rr2 = (rr2 - rr1) * (*ref) + rr1;

      gg2 = (gg2 - gg1) * (*ref) + gg1;

      bb2 = (bb2 - bb1) * (*ref) + bb1;

      aa2 = (aa2 - aa1) * (*ref) + aa1;

      ref++;

    }

    image_array[red] = rr2;

    image_array[gre] = gg2;

    image_array[blu] = bb2;

    image_array[alp] = aa2;

  }

}

}  // namespace

#include <stdexcept> /* std::domain_error(-) */</stdexcept>

void igs::density::change(float *image_array, const int height, const int width,

                          const int channels, /* 4(=RGBAでなければならない) */

                          const float *ref, const double density) {

  if (igs::image::rgba::siz != channels) {

    throw std::domain_error("Bad channels,Not rgba");

  }

  change_(image_array, height, width, channels, ref, density);

}