updated focal estimation (opencv_stitching) + refactoring

modules/stitching/autocalib.cpp

@@ -76,35 +76,46 @@ void focalsFromHomography(const Mat& H, double &f0, double &f1, bool &f0_ok, boo
 }
 
 
-double estimateFocal(const vector<ImageFeatures> &features, const vector<MatchesInfo> &pairwise_matches)
+void estimateFocal(const vector<ImageFeatures> &features, const vector<MatchesInfo> &pairwise_matches, 
+                   vector<double> &focals)
 {
     const int num_images = static_cast<int>(features.size());
+    focals.resize(num_images);
 
-    vector<double> focals;
-    for (int src_idx = 0; src_idx < num_images; ++src_idx)
-    {
-        for (int dst_idx = 0; dst_idx < num_images; ++dst_idx)
+    vector<vector<double> > all_focals(num_images);
+
+    for (int i = 0; i < num_images; ++i)
+    {        
+        for (int j = 0; j < num_images; ++j)
         {
-            const MatchesInfo &m = pairwise_matches[src_idx*num_images + dst_idx];
+            const MatchesInfo &m = pairwise_matches[i*num_images + j];
             if (m.H.empty())
                 continue;
 
             double f0, f1;
             bool f0ok, f1ok;
             focalsFromHomography(m.H, f0, f1, f0ok, f1ok);
-            if (f0ok && f1ok) focals.push_back(sqrt(f0*f1));
+            if (f0ok && f1ok) 
+            {
+                all_focals[i].push_back(f0);
+                all_focals[j].push_back(f1);
+            }
         }
     }
 
-    if (static_cast<int>(focals.size()) >= num_images * (num_images - 1) / 2)
+    for (int i = 0; i < num_images; ++i)
     {
-        nth_element(focals.begin(), focals.end(), focals.begin() + focals.size()/2);
-        return focals[focals.size()/2];
-    }
+        if (all_focals[i].size() > 0)
+        {
+            nth_element(all_focals[i].begin(), all_focals[i].end(), 
+                        all_focals[i].begin() + all_focals[i].size()/2);
+            focals[i] = all_focals[i][all_focals[i].size()/2];
+        }
+        else
+        {
+            LOGLN("Can't estimate focal length #" << i << ", will use naive approach");
+            focals[i] = features[i].img_size.width + features[i].img_size.height;
+        }
 
-    LOGLN("Can't estimate focal length, will use naive approach");
-    double focals_sum = 0;
-    for (int i = 0; i < num_images; ++i)
-        focals_sum += features[i].img_size.width + features[i].img_size.height;
-    return focals_sum / num_images;
+    }
 }

modules/stitching/autocalib.hpp

@@ -49,6 +49,7 @@
 // by Heung-Yeung Shum and Richard Szeliski.
 void focalsFromHomography(const cv::Mat &H, double &f0, double &f1, bool &f0_ok, bool &f1_ok);
 
-double estimateFocal(const std::vector<ImageFeatures> &features, const std::vector<MatchesInfo> &pairwise_matches);
+void estimateFocal(const std::vector<ImageFeatures> &features, const std::vector<MatchesInfo> &pairwise_matches, 
+                   std::vector<double> &focals);
 
 #endif // __OPENCV_AUTOCALIB_HPP__

modules/stitching/blenders.cpp

@@ -185,6 +185,11 @@ void MultiBandBlender::feed(const Mat &img, const Mat &mask, Point tl)
     CV_Assert(img.type() == CV_16SC3);
     CV_Assert(mask.type() == CV_8U);
 
+    //int gap = 10 * (1 << num_bands_);
+    //Point tl_new(max(dst_roi_.x, tl.x - gap), 
+    //             max(dst_roi_.y, tl.y - gap));
+    //Point br_new(min(dst_roi_.br().x, tl.x + img.cols + gap), 
+    //             min(dst_roi_.br().y, tl.y + img.rows + gap));
     Point tl_new(dst_roi_.tl());
     Point br_new(dst_roi_.br());
     int top = tl.y - tl_new.y;
@@ -215,8 +220,10 @@ void MultiBandBlender::feed(const Mat &img, const Mat &mask, Point tl)
     // Add weighted layer of the source image to the final Laplacian pyramid layer
     for (int i = 0; i <= num_bands_; ++i)
     {
-        int dx = 0;//(tl_new.x >> i) - (dst_roi_.x >> i);
-        int dy = 0;//(tl_new.y >> i) - (dst_roi_.y >> i);
+        int dx = 0;
+        int dy = 0;
+        //int dx = (tl_new.x >> i) - (dst_roi_.x >> i);
+        //int dy = (tl_new.y >> i) - (dst_roi_.y >> i);
 
         for (int y = 0; y < src_pyr_laplace[i].rows; ++y)
         {

modules/stitching/matchers.cpp

@@ -288,8 +288,11 @@ void FeaturesMatcher::operator ()(const vector<ImageFeatures> &features, vector<
 
 //////////////////////////////////////////////////////////////////////////////
 
-namespace
+namespace 
 {
+    // These two classes are aimed to find features matches only, not to 
+    // estimate homography
+
     class CpuMatcher : public FeaturesMatcher
     {
     public:
@@ -300,10 +303,24 @@ namespace
         float match_conf_;
     };
 
+
+    class GpuMatcher : public FeaturesMatcher
+    {
+    public:
+        GpuMatcher(float match_conf) : match_conf_(match_conf) {}
+        void match(const ImageFeatures &features1, const ImageFeatures &features2, MatchesInfo& matches_info);
+
+    private:
+        float match_conf_;
+        GpuMat descriptors1_;
+        GpuMat descriptors2_;
+        GpuMat train_idx_, distance_, all_dist_;
+    };
+
+
     void CpuMatcher::match(const ImageFeatures &features1, const ImageFeatures &features2, MatchesInfo& matches_info)
     {
         matches_info.matches.clear();
-
         BruteForceMatcher< L2<float> > matcher;
         vector< vector<DMatch> > pair_matches;
 
@@ -332,34 +349,19 @@ namespace
                 matches_info.matches.push_back(DMatch(m0.trainIdx, m0.queryIdx, m0.distance));
         }
     }
-        
-    class GpuMatcher : public FeaturesMatcher
-    {
-    public:
-        GpuMatcher(float match_conf) : match_conf_(match_conf) {}
-        void match(const ImageFeatures &features1, const ImageFeatures &features2, MatchesInfo& matches_info);
-
-    private:
-        float match_conf_;
-        GpuMat descriptors1_;
-        GpuMat descriptors2_;
-        GpuMat trainIdx_, distance_, allDist_;
-    };
+       
 
     void GpuMatcher::match(const ImageFeatures &features1, const ImageFeatures &features2, MatchesInfo& matches_info)
     {
-        matches_info.matches.clear();
-
-        BruteForceMatcher_GPU< L2<float> > matcher;
-        
+        matches_info.matches.clear();       
         descriptors1_.upload(features1.descriptors);
         descriptors2_.upload(features2.descriptors);
-
+        BruteForceMatcher_GPU< L2<float> > matcher;
         vector< vector<DMatch> > pair_matches;
 
         // Find 1->2 matches
-        matcher.knnMatch(descriptors1_, descriptors2_, trainIdx_, distance_, allDist_, 2);
-        matcher.knnMatchDownload(trainIdx_, distance_, pair_matches);
+        matcher.knnMatch(descriptors1_, descriptors2_, train_idx_, distance_, all_dist_, 2);
+        matcher.knnMatchDownload(train_idx_, distance_, pair_matches);
         for (size_t i = 0; i < pair_matches.size(); ++i)
         {
             if (pair_matches[i].size() < 2)
@@ -376,8 +378,8 @@ namespace
 
         // Find 2->1 matches
         pair_matches.clear();
-        matcher.knnMatch(descriptors2_, descriptors1_, trainIdx_, distance_, allDist_, 2);
-        matcher.knnMatchDownload(trainIdx_, distance_, pair_matches);
+        matcher.knnMatch(descriptors2_, descriptors1_, train_idx_, distance_, all_dist_, 2);
+        matcher.knnMatchDownload(train_idx_, distance_, pair_matches);
         for (size_t i = 0; i < pair_matches.size(); ++i)
         {
             if (pair_matches[i].size() < 2)
@@ -392,7 +394,9 @@ namespace
                 matches_info.matches.push_back(DMatch(m0.trainIdx, m0.queryIdx, m0.distance));
         }
     }
-}
+
+} // anonymous namespace
+
 
 BestOf2NearestMatcher::BestOf2NearestMatcher(bool try_use_gpu, float match_conf, int num_matches_thresh1, int num_matches_thresh2)
 {

modules/stitching/matchers.hpp

@@ -97,16 +97,18 @@ class FeaturesMatcher
 {
 public:
     virtual ~FeaturesMatcher() {}
-    void operator ()(const ImageFeatures &features1, const ImageFeatures &features2, MatchesInfo& matches_info) 
-    { 
-        match(features1, features2, matches_info);     
-    }
+
+    void operator ()(const ImageFeatures &features1, const ImageFeatures &features2, 
+                     MatchesInfo& matches_info) { match(features1, features2, matches_info); }
     void operator ()(const std::vector<ImageFeatures> &features, std::vector<MatchesInfo> &pairwise_matches);
+
     bool isThreadSafe() const { return is_thread_safe_; }
 
 protected:
     FeaturesMatcher(bool is_thread_safe = false) : is_thread_safe_(is_thread_safe) {}
-    virtual void match(const ImageFeatures &features1, const ImageFeatures &features2, MatchesInfo& matches_info) = 0;
+
+    virtual void match(const ImageFeatures &features1, const ImageFeatures &features2, 
+                       MatchesInfo& matches_info) = 0;
 
     bool is_thread_safe_;
 };
@@ -115,14 +117,14 @@ protected:
 class BestOf2NearestMatcher : public FeaturesMatcher
 {
 public:
-    BestOf2NearestMatcher(bool try_use_gpu = true, float match_conf = 0.55f, int num_matches_thresh1 = 6, int num_matches_thresh2 = 6);
+    BestOf2NearestMatcher(bool try_use_gpu = true, float match_conf = 0.55f, int num_matches_thresh1 = 6, 
+                          int num_matches_thresh2 = 6);
 
 protected:
     void match(const ImageFeatures &features1, const ImageFeatures &features2, MatchesInfo &matches_info);
 
     int num_matches_thresh1_;
     int num_matches_thresh2_;
-
     cv::Ptr<FeaturesMatcher> impl_;
 };
 

modules/stitching/motion_estimators.cpp

@@ -109,10 +109,11 @@ void HomographyBasedEstimator::estimate(const vector<ImageFeatures> &features, c
     const int num_images = static_cast<int>(features.size());
 
     // Estimate focal length and set it for all cameras
-    double focal = estimateFocal(features, pairwise_matches);
+    vector<double> focals;
+    estimateFocal(features, pairwise_matches, focals);
     cameras.resize(num_images);
     for (int i = 0; i < num_images; ++i)
-        cameras[i].focal = focal;
+        cameras[i].focal = focals[i];
 
     // Restore global motion
     Graph span_tree;