From e4eeeb6ac25deb2265f687d552ffbdf3e69dc43b Mon Sep 17 00:00:00 2001
From: Phuntsok Drak-pa <phundrak@phundrak.fr>
Date: Thu, 16 May 2019 23:46:56 +0200
Subject: [PATCH] optimized difference computing

---
 include/genimg/methods.hh |  9 +++------
 src/methods.cc            | 24 ++----------------------
 2 files changed, 5 insertions(+), 28 deletions(-)

diff --git a/include/genimg/methods.hh b/include/genimg/methods.hh
index 403fd39..885958a 100644
--- a/include/genimg/methods.hh
+++ b/include/genimg/methods.hh
@@ -58,10 +58,6 @@ protected:
 private:
   // methods //////////////////////////////////////////////////////////////////
 
-  /// \brief Calculates the euclidian distance between two images
-  [[nodiscard]] auto euclidian_distance(cv::Mat const &t_img) const noexcept
-      -> double;
-
   /// \brief Creates and returns a random color
   [[nodiscard]] auto random_color() const noexcept;
 
@@ -119,8 +115,9 @@ private:
   mutable std::mutex
       colors_mutex_{}; /*!< Thread mutex for color set generation */
   std::string const output_path_{}; /*!< Write path for the generated image */
-  double diff_{euclidian_distance(generated_image_)}; /*!< Euclidian difference
-                         between \ref reference_ and \ref generated_image_ */
+  double diff_{
+      cv::norm(reference_, generated_image_)}; /*!< Euclidian difference
+                between \ref reference_ and \ref generated_image_ */
   int const total_iterations_{0}; /*!< Number of iterations to perform */
   int remaining_iter_{
       total_iterations_}; /*!< Remaining iterations to perform */
diff --git a/src/methods.cc b/src/methods.cc
index d09ae2c..9e1fe1c 100644
--- a/src/methods.cc
+++ b/src/methods.cc
@@ -133,26 +133,6 @@ void ImageManipulator::exec_method(int const t_nb_method,
 
 // methods ////////////////////////////////////////////////////////////////////
 
-/**
- *  Calculates the euclidian distance between the reference image and the image
- *  passed as an argument
- *
- *  \param t_img Image with which the distance is computed
- *  \return double
- */
-[[nodiscard]] auto
-ImageManipulator::euclidian_distance(cv::Mat const &t_img) const noexcept
-    -> double
-{
-  double euclidian = 0.0;
-  for (auto itr1 = reference_.begin<uchar>(), itr2 = t_img.begin<uchar>();
-       itr1 != reference_.end<uchar>() && itr2 != t_img.end<uchar>();
-       ++itr1, ++itr2) {
-    euclidian += std::pow(*itr1 - *itr2, 2);
-  }
-  return std::sqrt(euclidian);
-}
-
 /**
  *  \return cv::Scalar
  */
@@ -203,7 +183,7 @@ ImageManipulator::create_candidate(bool const t_controlled_size = false)
   draw_shape(temp_img, cv::Scalar{static_cast<double>(color[0]),
                                   static_cast<double>(color[1]),
                                   static_cast<double>(color[2])});
-  auto new_diff = euclidian_distance(temp_img);
+  const auto new_diff = cv::norm(reference_, temp_img);
   return (new_diff < diff_)
              ? std::optional<std::pair<cv::Mat, double>>{std::make_pair(
                  std::move(temp_img), new_diff)}
@@ -339,7 +319,7 @@ void ImageManipulator::method1()
     auto temp_image = generated_image_.clone();
     create_shape();
     draw_shape(temp_image, random_color());
-    if (auto const new_diff = euclidian_distance(temp_image);
+    if (auto const new_diff = cv::norm(reference_, temp_image);
         new_diff < diff_) {
       update_gen_image(temp_image, new_diff);
     }