fixed some bugs in opencv_stitching

modules/stitching/autocalib.cpp

@@ -110,7 +110,7 @@ void estimateFocal(const vector<ImageFeatures> &features, const vector<MatchesIn
     }
     else
     {
-        nth_element(all_focals.begin(), all_focals.end(), all_focals.begin() + all_focals.size()/2);
+        nth_element(all_focals.begin(), all_focals.begin() + all_focals.size()/2, all_focals.end());
         for (int i = 0; i < num_images; ++i)
             focals[i] = all_focals[all_focals.size()/2];
     }

modules/stitching/exposure_compensate.cpp

@@ -62,7 +62,7 @@ void OverlapExposureCompensator::feed(const vector<Point> &corners, const vector
                                       const vector<Mat> &masks)
 {
     const int num_images = static_cast<int>(images.size());
-    Mat_<double> N(num_images, num_images); N.setTo(0);
+    Mat_<int> N(num_images, num_images); N.setTo(0);
     Mat_<double> I(num_images, num_images); I.setTo(0);
 
     Rect dst_roi = resultRoi(corners, images);
@@ -99,8 +99,8 @@ void OverlapExposureCompensator::feed(const vector<Point> &corners, const vector
                         }
                     }
                 }
-                I(i, j) = Isum1 / N(i, j);
-                I(j, i) = Isum2 / N(i, j);
+                I(i, j) = Isum1 / max(N(i, j), 1);
+                I(j, i) = Isum2 / max(N(i, j), 1);
             }
         }
     }

modules/stitching/main.cpp

@@ -341,8 +341,13 @@ int main(int argc, char* argv[])
     vector<Mat> img_subset;
     vector<string> img_names_subset;
     for (size_t i = 0; i < indices.size(); ++i)
+    {
         img_names_subset.push_back(img_names[indices[i]]);
+        img_subset.push_back(images[indices[i]]);
+    }
+
     img_names = img_names_subset;
+    images = img_subset;
 
     // Check if we still have enough images
     num_images = static_cast<int>(img_names.size());
@@ -393,7 +398,7 @@ int main(int argc, char* argv[])
         LOGLN("Camera #" << i << " focal length: " << cameras[i].focal);
         focals.push_back(cameras[i].focal);
     }
-    nth_element(focals.begin(), focals.end(), focals.begin() + focals.size() / 2);
+    nth_element(focals.begin(), focals.begin() + focals.size()/2, focals.end());
     float warped_image_scale = static_cast<float>(focals[focals.size() / 2]);
 
     LOGLN("Warping images (auxiliary)... ");

modules/stitching/matchers.cpp

@@ -265,7 +265,7 @@ void FeaturesMatcher::operator ()(const vector<ImageFeatures> &features, vector<
 
         // Leave k-nearest images
         int k = min(4, num_images);
-        nth_element(dists.begin(), dists.end(), dists.begin() + k);
+        nth_element(dists.begin(), dists.begin() + k, dists.end());
         for (int j = 0; j < k; ++j)
             is_near(i, dists[j].idx) = 1;
     }
@@ -273,7 +273,7 @@ void FeaturesMatcher::operator ()(const vector<ImageFeatures> &features, vector<
     vector<pair<int,int> > near_pairs;
     for (int i = 0; i < num_images - 1; ++i)
         for (int j = i + 1; j < num_images; ++j)
-            if (is_near(i, j))
+            if (is_near(i, j) || is_near(j, i))
                 near_pairs.push_back(make_pair(i, j));
 
     pairwise_matches.resize(num_images * num_images);