Merge remote-tracking branch 'upstream/3.4' into merge-3.4

samples/cpp/detect_blob.cpp

@@ -192,7 +192,7 @@ int main(int argc, char *argv[])
             imshow("Original", img);
             waitKey();
         }
-        catch (Exception& e)
+        catch (const Exception& e)
         {
             cout << "Feature : " << *itDesc << "\n";
             cout << e.msg << endl;

samples/cpp/detect_mser.cpp

@@ -523,7 +523,7 @@ int main(int argc, char *argv[])
             imshow(winName, result);
             imshow("Original", img);
         }
-        catch (Exception& e)
+        catch (const Exception& e)
         {
             cout << "Feature: " << *itDesc << "\n";
             cout << e.msg << endl;

samples/cpp/live_detect_qrcode.cpp

@@ -177,7 +177,7 @@ int showImageQRCodeDetect(string in, string out)
         {
             imwrite(out, color_src, compression_params);
         }
-        catch (cv::Exception& ex)
+        catch (const cv::Exception& ex)
         {
             cout << "Exception converting image to PNG format: ";
             cout << ex.what() << '\n';

samples/cpp/matchmethod_orb_akaze_brisk.cpp

@@ -147,15 +147,15 @@ int main(int argc, char *argv[])
                     desMethCmp.push_back(cumSumDist2);
                     waitKey();
                 }
-                catch (Exception& e)
-                    {
+                catch (const Exception& e)
+                {
                     cout << e.msg << endl;
                     cout << "Cumulative distance cannot be computed." << endl;
                     desMethCmp.push_back(-1);
-                    }
                 }
+            }
         }
-        catch (Exception& e)
+        catch (const Exception& e)
         {
             cout << "Feature : " << *itDesc << "\n";
             if (itMatcher != typeAlgoMatch.end())

samples/cpp/pca.cpp

@@ -141,7 +141,7 @@ int main(int argc, char** argv)
     // Read in the data. This can fail if not valid
     try {
         read_imgList(imgList, images);
-    } catch (cv::Exception& e) {
+    } catch (const cv::Exception& e) {
         cerr << "Error opening file \"" << imgList << "\". Reason: " << e.msg << endl;
         exit(1);
     }