Addded an option to visualize features used for image stabilization

Author: SBCV

modules/videostab/include/opencv2/videostab/global_motion.hpp

@@ -182,8 +182,13 @@ class CV_EXPORTS ImageMotionEstimatorBase
 
     virtual Mat estimate(const Mat &frame0, const Mat &frame1, bool *ok = 0) = 0;
 
+    void setFeatureVisualizationCallback(std::function<void(Mat)> featureVisualizationCallback) {
+        featureVisualizationCallback_ = std::bind(featureVisualizationCallback, std::placeholders::_1);
+    };
+
 protected:
     ImageMotionEstimatorBase(MotionModel model) { setMotionModel(model); }
+    std::function<void(Mat)> featureVisualizationCallback_;
 
 private:
     MotionModel motionModel_;

modules/videostab/samples/videostab.cpp

@@ -166,6 +166,8 @@ void printHelp()
             "      Set output file path explicitly. The default is stabilized.avi.\n"
             "  --fps=(<float_number>|auto)\n"
             "      Set output video FPS explicitly. By default the source FPS is used (auto).\n"
+            "  --vo=, --vis-output=(no|<file_path>)\n"
+            "      Set visualization output file path. The default is no.\n"
             "  -q, --quiet\n"
             "      Don't show output video frames.\n\n"
             "  -h, --help\n"
@@ -335,6 +337,7 @@ int main(int argc, const char **argv)
                 "{ gpu                      | no | }"
                 "{ o  output                | stabilized.avi | }"
                 "{ fps                      | auto | }"
+                "{ vo  vis-output           | no | }"
                 "{ q quiet                  |  | }"
                 "{ h help                   |  | }";
         CommandLineParser cmd(argc, argv, keys);
@@ -464,6 +467,26 @@ int main(int argc, const char **argv)
         // cast stabilizer to simple frame source interface to read stabilized frames
         stabilizedFrames.reset(dynamic_cast<IFrameSource*>(stabilizer));
 
+        // visWriter and visOutputPath must not be defined inside the if statement
+        VideoWriter visWriter;
+        string visOutputPath;
+        if (arg("vis-output") != "no") 
+        {
+            visOutputPath = arg("vis-output");
+            std::function<void(Mat)> featureVisualizationCallback = [&visWriter, &visOutputPath](Mat featureVisualization){ 
+                // init visWriter (once) and save visualization frame
+                if (!featureVisualization.empty()) {
+                    if (!visWriter.isOpened())
+                        visWriter.open(visOutputPath, VideoWriter::fourcc('X','V','I','D'),
+                                    outputFps, featureVisualization.size());
+                    visWriter << featureVisualization;        
+                } 
+            };
+            // must be called before
+            // "stabilizer->setMotionEstimator(makePtr<ToFileMotionWriter>(arg("save-motions"), stabilizer->motionEstimator()));"
+            stabilizer->motionEstimator()->setFeatureVisualizationCallback(featureVisualizationCallback);
+        } 
+
         MotionModel model = stabilizer->motionEstimator()->motionModel();
         if (arg("load-motions") != "no")
         {

modules/videostab/src/global_motion.cpp

@@ -727,8 +727,12 @@ Mat KeypointBasedMotionEstimator::estimate(InputArray frame0, InputArray frame1,
     // find keypoints
     detector_->detect(frame0, keypointsPrev_);
     if (keypointsPrev_.empty())
+    {
+        if (featureVisualizationCallback_)
+            featureVisualizationCallback_(Mat());
         return Mat::eye(3, 3, CV_32F);
-
+    }
+        
     // extract points from keypoints
     pointsPrev_.resize(keypointsPrev_.size());
     for (size_t i = 0; i < keypointsPrev_.size(); ++i)
@@ -777,6 +781,23 @@ Mat KeypointBasedMotionEstimator::estimate(InputArray frame0, InputArray frame1,
         }
     }
 
+    if (featureVisualizationCallback_) {
+        Mat featureVisualizationPrev;
+        drawKeypoints(frame0, keypointsPrev_, featureVisualizationPrev, 
+            Scalar(0, 0, 255), DrawMatchesFlags::DEFAULT);
+
+        std::vector<KeyPoint> keypointsPrevGood;
+        keypointsPrevGood.reserve(pointsPrevGood_.size());
+
+        for( size_t i = 0; i < pointsPrevGood_.size(); ++i) {
+            keypointsPrevGood.push_back(KeyPoint(pointsPrevGood_[i], 1.f));
+        }
+        drawKeypoints(frame0, keypointsPrevGood, featureVisualizationPrev, 
+            Scalar(0, 255, 0), DrawMatchesFlags::DRAW_OVER_OUTIMG);
+   
+        featureVisualizationCallback_(featureVisualizationPrev);    
+    }
+
     // estimate motion
     return motionEstimator_->estimate(pointsPrevGood_, pointsGood_, ok);
 }