Function GetDistance

libs/transit/world_feed/color_picker.cpp:20–39

}

double GetDistance(dp::Color const & color1, dp::Color const & color2)
{
  auto [r1, g1, b1] = GetColors(color1);
  auto [r2, g2, b2] = GetColors(color2);

  // We use the cmetric (Color metric) for calculating the distance between two colors.
  // https://en.wikipedia.org/wiki/Color_difference
  // It reflects human perception of closest match for a specific colour. The formula weights RGB
  // values to better fit eye perception and performs well at proper determinations of colors
  // contributions, brightness of these colors, and degree to which human vision has less tolerance
  // for these colors.
  double const redMean = (r1 + r2) / 2.0;

  double const redDelta = r1 - r2;
  double const greenDelta = g1 - g2;
  double const blueDelta = b1 - b2;

  return (2.0 + redMean / 256.0) * redDelta * redDelta + 4 * greenDelta * greenDelta +
         (2.0 + (255.0 - redMean) / 256.0) * blueDelta * blueDelta;
}
}  // namespace

namespace transit