piphoto/colorchecker.h

#pragma once

#include <array>
#include <numeric>

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

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

constexpr std::array<Color, 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>
std::array<Coord, kColorCheckerSrgb.size()> FindClosest(const Image<X, Y>& image) {
  std::array<Coord, 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 ScoreImage(const Image<X, Y>& image) {
  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>
std::unique_ptr<Image<X, Y>> HighlightClosest(const Image<X, Y>& image) {
  auto out = std::make_unique<Image<X, Y>>(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.x) - 5, std::max(5U, coord.y) - 5}, kBlack, 10);
    out->DrawSquare({std::max(6U, coord.x) - 6, std::max(6U, coord.y) - 6}, color, 12);
    out->DrawSquare({std::max(7U, coord.x) - 7, std::max(7U, coord.y) - 7}, color, 14);
    out->DrawSquare({std::max(8U, coord.x) - 8, std::max(8U, coord.y) - 8}, color, 16);
    out->DrawSquare({std::max(9U, coord.x) - 9, std::max(9U, coord.y) - 9}, kWhite, 18);
  }
  return out;
}