piphoto/colorchecker.h

#pragma once

#include <array>
#include <cstdint>
#include <numeric>

#include "color.h"
#include "colors.h"
#include "coord.h"
#include "image.h"
#include "lut.h"
#include "minimum.h"

// Maximum LUT size that has each point adjacent to at least one ColorChecker color.
typedef Lut3d<4, 3, 3> ColorCheckerLut3d;

constexpr std::array<RgbColor, 24> kColorCheckerSrgb = {{
  {{{{0x7300, 0x5200, 0x4400}}}},
  {{{{0xc200, 0x9600, 0x8200}}}},
  {{{{0x6200, 0x7a00, 0x9d00}}}},
  {{{{0x5700, 0x6c00, 0x4300}}}},
  {{{{0x8500, 0x8000, 0xb100}}}},
  {{{{0x6700, 0xbd00, 0xaa00}}}},
  {{{{0xd600, 0x7e00, 0x2c00}}}},
  {{{{0x5000, 0x5b00, 0xa600}}}},
  {{{{0xc100, 0x5a00, 0x6300}}}},
  {{{{0x5e00, 0x3c00, 0x6c00}}}},
  {{{{0x9d00, 0xbc00, 0x4000}}}},
  {{{{0xe000, 0xa300, 0x2e00}}}},
  {{{{0x3800, 0x3d00, 0x9600}}}},
  {{{{0x4600, 0x9400, 0x4900}}}},
  {{{{0xaf00, 0x3600, 0x3c00}}}},
  {{{{0xe700, 0xc700, 0x1f00}}}},
  {{{{0xbb00, 0x5600, 0x9500}}}},
  {{{{0x0800, 0x8500, 0xa100}}}},
  {{{{0xf300, 0xf300, 0xf200}}}},
  {{{{0xc800, 0xc800, 0xc800}}}},
  {{{{0xa000, 0xa000, 0xa000}}}},
  {{{{0x7a00, 0x7a00, 0x7900}}}},
  {{{{0x5500, 0x5500, 0x5500}}}},
  {{{{0x3400, 0x3400, 0x3400}}}},
}};

template <uint32_t X, uint32_t Y, uint32_t C>
std::array<Coord<2>, kColorCheckerSrgb.size()> FindClosest(const Image<X, Y, C>& image) {
  static_assert(C == 3);

  std::array<Coord<2>, kColorCheckerSrgb.size()> closest;
  std::array<uint32_t, kColorCheckerSrgb.size()> diff;
  diff.fill(UINT32_MAX);

  for (uint32_t y = 0; y < Y; ++y) {
    const auto& row = image.at(y);

    for (uint32_t x = 0; x < X; ++x) {
      const auto& pixel = row.at(x);

      for (uint32_t cc = 0; cc < kColorCheckerSrgb.size(); ++cc) {
        auto pixel_diff = pixel.Difference(kColorCheckerSrgb.at(cc));
        if (pixel_diff < diff.at(cc)) {
          diff.at(cc) = pixel_diff;
          closest.at(cc) = {{{x, y}}};
        }
      }
    }
  }

  return closest;
}

template <uint32_t X, uint32_t Y, uint32_t C>
uint32_t ScoreImage(const Image<X, Y, C>& image) {
  static_assert(C == 3);

  std::array<uint32_t, kColorCheckerSrgb.size()> diff;
  diff.fill(UINT32_MAX);

  for (uint32_t y = 0; y < Y; ++y) {
    const auto& row = image.at(y);

    for (uint32_t x = 0; x < X; ++x) {
      const auto& pixel = row.at(x);

      for (uint32_t cc = 0; cc < kColorCheckerSrgb.size(); ++cc) {
        auto pixel_diff = pixel.Difference(kColorCheckerSrgb.at(cc));
        if (pixel_diff < diff.at(cc)) {
          diff.at(cc) = pixel_diff;
        }
      }
    }
  }

  return std::accumulate(diff.begin(), diff.end(), UINT32_C(0));
}

template <uint32_t X, uint32_t Y, uint32_t C>
std::unique_ptr<Image<X, Y, C>> HighlightClosest(const Image<X, Y, C>& image) {
  static_assert(C == 3);

  auto out = std::make_unique<Image<X, Y, C>>(image);

  auto closest = FindClosest(*out);
  for (uint32_t cc = 0; cc < kColorCheckerSrgb.size(); ++cc) {
    const auto& coord = closest.at(cc);
    const auto& color = kColorCheckerSrgb.at(cc);
    out->DrawSquare({{{std::max(5U, coord.at(0)) - 5, std::max(5U, coord.at(1)) - 5}}}, kBlack, 10);
    out->DrawSquare({{{std::max(6U, coord.at(0)) - 6, std::max(6U, coord.at(1)) - 6}}}, color, 12);
    out->DrawSquare({{{std::max(7U, coord.at(0)) - 7, std::max(7U, coord.at(1)) - 7}}}, color, 14);
    out->DrawSquare({{{std::max(8U, coord.at(0)) - 8, std::max(8U, coord.at(1)) - 8}}}, color, 16);
    out->DrawSquare({{{std::max(9U, coord.at(0)) - 9, std::max(9U, coord.at(1)) - 9}}}, kWhite, 18);
  }
  return out;
}

template <uint32_t P, uint32_t LUT_X, uint32_t LUT_Y, uint32_t LUT_Z, uint32_t IMG_X, uint32_t IMG_Y, uint32_t C>
uint32_t OptimizeLut(const Image<IMG_X, IMG_Y, C>& image, Lut3d<LUT_X, LUT_Y, LUT_Z>* lut) {
  static_assert(C == 3);

  auto snapshot = *lut;
  uint32_t diff = 0;

  for (uint32_t x = 0; x < LUT_X; ++x) {
    auto& rect = lut->at(x);

    for (uint32_t y = 0; y < LUT_Y; ++y) {
      auto& row = rect.at(y);

      for (uint32_t z = 0; z < LUT_Z; ++z) {
        auto& color = row.at(z);

        std::cout << Coord<3>{{{x, y, z}}} << std::endl;

        for (uint32_t c = 0; c < C; ++c) {
          auto& channel = color.at(c);

          auto min = FindPossibleMinimum<uint32_t, uint32_t, 4>(
            0, UINT16_MAX,
            [&image, &snapshot, x, y, z, c](uint32_t val) {
              auto test_lut = snapshot;
              test_lut.at(x).at(y).at(z).at(c) = val;
              return ScoreImage(*test_lut.MapImage(image));
            });
          // Magic value of 8 is the number of points making up a square, so the number
          // of points that control any given given LUT mapping.
          auto new_value = Interpolate(channel, min, UINT32_C(1), UINT32_C(8));
          std::cout << "\tC" << c << ": " << channel << " -> " << new_value << " (interpolated from " << min << ")" << std::endl;
          diff += AbsDiff(channel, new_value);
          channel = new_value;
        }
      }
    }
  }

  return diff;
}