Fix rounding in StructuredEdgeDetection

modules/ximgproc/src/structured_edge_detection.cpp

@@ -235,6 +235,7 @@ static void gradientHist(const cv::Mat &src, cv::Mat &magnitude, cv::Mat &histog
     magnitude /= imsmooth( magnitude, gnrmRad )
         + 0.01*cv::Mat::ones( magnitude.size(), magnitude.type() );
 
+    int pHistSize = histogram.cols*histogram.channels() - 1;
     for (int i = 0; i < phase.rows; ++i)
     {
         const float *pPhase = phase.ptr<float>(i);
@@ -243,7 +244,11 @@ static void gradientHist(const cv::Mat &src, cv::Mat &magnitude, cv::Mat &histog
         float *pHist = histogram.ptr<float>(i/pSize);
 
         for (int j = 0; j < phase.cols; ++j)
-            pHist[cvRound((j/pSize + pPhase[j])*nBins)] += pMagn[j] / CV_SQR(pSize);
+        {
+            int index  = cvRound((j/pSize + pPhase[j])*nBins);
+            index = std::max(0, std::min(index, pHistSize));
+            pHist[index] += pMagn[j] / CV_SQR(pSize);
+        }
     }
 }