Merge branch '224-compute-entropy-mi' into 'release'

Resolve "IM: Calcul de l'entropie et de l'IM en cpp"

See merge request 3d/PandoraBox/pandora2d!187

pandora2d/matching_cost_cpp/include/mutual_information.hpp

@@ -0,0 +1,75 @@
+/* Copyright (c) 2024 Centre National d'Etudes Spatiales (CNES).
+ *
+ * This file is part of PANDORA2D
+ *
+ *     https://github.com/CNES/Pandora2D
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+This module contains functions associated to the mutual information in cpp.
+*/
+
+#ifndef MUTUAL_INFORMATION_HPP
+#define MUTUAL_INFORMATION_HPP
+
+#include "histogram1D.hpp"
+#include "histogram2D.hpp"
+
+/**
+ * @brief Compute entropy
+ *
+ * @tparam T hist1D or hist2D
+ * @param nb_pixel of the image
+ * @param hist to iterate
+ * @return double entropy
+ */
+template <typename T>
+double get_entropy(const double nb_pixel, const T &hist);
+
+/**
+ * @brief Compute entropy 1D of an image
+ *
+ * Entropy1D(img) = - sum(bin_value/nb_pixel * log2(bin_value/nb_pixel))
+ * for each bin_value in Hist1D(img)
+ *
+ * @param img
+ * @return double entropy1D value
+ */
+double calculate_entropy1D(const Eigen::MatrixXd &img);
+
+/**
+ * @brief Compute entropy 2D of two images
+ *
+ * Entropy2D(img_l, img_r) = - sum(bin_value/nb_pixel * log2(bin_value/nb_pixel))
+ * for each bin_value in Hist2D(img_l, img_r)
+ *
+ * @param img_l left image
+ * @param img_r right image
+ * @return double entropy 2D value
+ */
+double calculate_entropy2D(const Eigen::MatrixXd &img_l, const Eigen::MatrixXd &img_r);
+
+/**
+ * @brief Compute mutual information between two images
+ *
+ * MutualInformation(img_l,img_r) = Entropy1D(img_l) + Entropy1D(img_r) - Entropy2D(img_l, img_r)
+ *
+ * @param img_l left image
+ * @param img_r right image
+ * @return double mutual information value
+ */
+double calculate_mutual_information(const Eigen::MatrixXd &img_l, const Eigen::MatrixXd &img_r);
+
+#endif

pandora2d/matching_cost_cpp/meson.build

@@ -1,5 +1,6 @@
 matching_cost_includes = include_directories('include')
-matching_cost_src = files('src/histogram1D.cpp', 'src/histogram2D.cpp', 'src/operation.cpp', 'src/bin.cpp')
+matching_cost_src = files('src/histogram1D.cpp', 'src/histogram2D.cpp', 'src/operation.cpp', 'src/bin.cpp', 
+                            'src/mutual_information.cpp')
 
 py.extension_module(
     'matching_cost_cpp',

pandora2d/matching_cost_cpp/src/mutual_information.cpp

@@ -0,0 +1,106 @@
+/* Copyright (c) 2024 Centre National d'Etudes Spatiales (CNES).
+ *
+ * This file is part of PANDORA2D
+ *
+ *     https://github.com/CNES/Pandora2D
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+This module contains functions associated to the mutual information in cpp.
+*/
+
+#include "mutual_information.hpp"
+
+/**
+ * @brief Compute entropy
+ * 
+ * @tparam T hist1D or hist2D
+ * @param nb_pixel of the image
+ * @param hist to iterate
+ * @return double entropy
+ */
+template <typename T> 
+double get_entropy(const double nb_pixel, const T &hist){
+
+    double entropy = 0.0 ; 
+
+    for (auto bin_value : hist.values().reshaped())
+    {
+        if (bin_value != 0.)
+        {
+            entropy -= bin_value / nb_pixel * std::log2(bin_value / nb_pixel);
+        }
+    };
+
+    // Entropy cannot be negative
+    return entropy < 0. ? 0. : entropy ; 
+
+};
+
+/**
+ * @brief Compute entropy 1D of an image
+ * 
+ * Entropy1D(img) = - sum(bin_value/nb_pixel * log2(bin_value/nb_pixel))
+ * for each bin_value in Hist1D(img)
+ *
+ * @param img
+ * @return double entropy1D
+ */
+double calculate_entropy1D(const Eigen::MatrixXd &img)
+{
+
+    auto nb_pixel = static_cast<double>(img.size());
+    auto hist_1D = calculate_histogram1D(img);
+
+    return get_entropy<Histogram1D>(nb_pixel, hist_1D);
+};
+
+/**
+ * @brief Compute entropy 2D of two images
+ * 
+ * Entropy2D(img_l, img_r) = - sum(bin_value/nb_pixel * log2(bin_value/nb_pixel))
+ * for each bin_value in Hist2D(img_l, img_r)
+ *
+ * @param img_l left image
+ * @param img_r right image
+ * @return double entropy 2D
+ */
+double calculate_entropy2D(const Eigen::MatrixXd &img_l, const Eigen::MatrixXd &img_r)
+{
+
+    // same size for left and right images
+    auto nb_pixel = static_cast<double>(img_l.size());
+    auto hist_2D = calculate_histogram2D(img_l, img_r);
+
+    return get_entropy<Histogram2D>(nb_pixel, hist_2D);
+};
+
+/**
+ * @brief Compute mutual information between two images
+ * 
+ * MutualInformation(img_l,img_r) = Entropy1D(img_l) + Entropy1D(img_r) - Entropy2D(img_l, img_r)
+ *
+ * @param img_l left image
+ * @param img_r right image
+ * @return double mutual information value
+ */
+double calculate_mutual_information(const Eigen::MatrixXd &img_l, const Eigen::MatrixXd &img_r)
+{
+
+    double mutual_information = calculate_entropy1D(img_l) + calculate_entropy1D(img_r) 
+                                - calculate_entropy2D(img_l, img_r);
+
+    return mutual_information;
+}

tests/unit_tests/test_cpp/test_matching_cost/meson.build

@@ -36,4 +36,14 @@ test(
         include_directories:matching_cost_includes,
         dependencies: [eigen_dep, doctest_dep],
     ),
+)
+
+test(
+    'MutualInformation',
+    executable(
+        'test_mutual_information',
+        ['test_mutual_information.cpp', matching_cost_src],
+        include_directories:matching_cost_includes,
+        dependencies: [eigen_dep, doctest_dep],
+    ),
 )