From d33d37ffd9af0367aa3ee637a3f4252ac1271930 Mon Sep 17 00:00:00 2001
From: Tetragramm <gaussgun+git@gmail.com>
Date: Wed, 4 Jan 2017 18:38:46 -0600
Subject: [PATCH 1/2] Add check for all zero moments. If one of the shapes is
 empty, the match would return zero distance between the shapes even when the
 other one had content. It now returns DBL_MAX if no moments had value.

---
 modules/imgproc/src/matchcontours.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/modules/imgproc/src/matchcontours.cpp b/modules/imgproc/src/matchcontours.cpp
index 1a371677bf..f848bd59a8 100644
--- a/modules/imgproc/src/matchcontours.cpp
+++ b/modules/imgproc/src/matchcontours.cpp
@@ -50,6 +50,7 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
     double eps = 1.e-5;
     double mmm;
     double result = 0;
+    bool anyResults = false;
 
     HuMoments( moments(contour1), ma );
     HuMoments( moments(contour2), mb );
@@ -80,6 +81,7 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
                 ama = 1. / (sma * log10( ama ));
                 amb = 1. / (smb * log10( amb ));
                 result += fabs( -ama + amb );
+                anyResults = true;
             }
         }
         break;
@@ -108,6 +110,7 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
                 ama = sma * log10( ama );
                 amb = smb * log10( amb );
                 result += fabs( -ama + amb );
+                anyResults = true;
             }
         }
         break;
@@ -138,6 +141,7 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
                 mmm = fabs( (ama - amb) / ama );
                 if( result < mmm )
                     result = mmm;
+                anyResults = true;
             }
         }
         break;
@@ -145,6 +149,9 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
         CV_Error( CV_StsBadArg, "Unknown comparison method" );
     }
 
+    if (!anyResults)
+        result = DBL_MAX;
+
     return result;
 }
 

From 7cc0b0f93ea3fa8131b478bc9483199ae933ebe7 Mon Sep 17 00:00:00 2001
From: Tetragramm <gaussgun+git@gmail.com>
Date: Tue, 10 Jan 2017 21:38:31 -0600
Subject: [PATCH 2/2] Add case including both moments empty.

---
 modules/imgproc/src/matchcontours.cpp | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/modules/imgproc/src/matchcontours.cpp b/modules/imgproc/src/matchcontours.cpp
index f848bd59a8..2a0c5df330 100644
--- a/modules/imgproc/src/matchcontours.cpp
+++ b/modules/imgproc/src/matchcontours.cpp
@@ -50,7 +50,7 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
     double eps = 1.e-5;
     double mmm;
     double result = 0;
-    bool anyResults = false;
+    bool anyA = false, anyB = false;
 
     HuMoments( moments(contour1), ma );
     HuMoments( moments(contour2), mb );
@@ -63,6 +63,11 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
             double ama = fabs( ma[i] );
             double amb = fabs( mb[i] );
 
+            if (ama > 0)
+                anyA = true;
+            if (amb > 0)
+                anyB = true;
+
             if( ma[i] > 0 )
                 sma = 1;
             else if( ma[i] < 0 )
@@ -81,7 +86,6 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
                 ama = 1. / (sma * log10( ama ));
                 amb = 1. / (smb * log10( amb ));
                 result += fabs( -ama + amb );
-                anyResults = true;
             }
         }
         break;
@@ -92,6 +96,11 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
             double ama = fabs( ma[i] );
             double amb = fabs( mb[i] );
 
+            if (ama > 0)
+                anyA = true;
+            if (amb > 0)
+                anyB = true;
+
             if( ma[i] > 0 )
                 sma = 1;
             else if( ma[i] < 0 )
@@ -110,7 +119,6 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
                 ama = sma * log10( ama );
                 amb = smb * log10( amb );
                 result += fabs( -ama + amb );
-                anyResults = true;
             }
         }
         break;
@@ -121,6 +129,11 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
             double ama = fabs( ma[i] );
             double amb = fabs( mb[i] );
 
+            if (ama > 0)
+                anyA = true;
+            if (amb > 0)
+                anyB = true;
+
             if( ma[i] > 0 )
                 sma = 1;
             else if( ma[i] < 0 )
@@ -141,7 +154,6 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
                 mmm = fabs( (ama - amb) / ama );
                 if( result < mmm )
                     result = mmm;
-                anyResults = true;
             }
         }
         break;
@@ -149,7 +161,10 @@ double cv::matchShapes(InputArray contour1, InputArray contour2, int method, dou
         CV_Error( CV_StsBadArg, "Unknown comparison method" );
     }
 
-    if (!anyResults)
+    //If anyA and anyB are both true, the result is correct.
+    //If anyA and anyB are both false, the distance is 0, perfect match.
+    //If only one is true, then it's a false 0 and return large error.
+    if (anyA != anyB)
         result = DBL_MAX;
 
     return result;