Merge pull request #13910 from x3lif:Issue_13908

* Fix Issue 13908

Allocate the matrix _Jo only when the solver needs it (ie when solver.state == CvLevMarq::CALC_J)

* Fix calib3D unit test

Fix _Jo allocation when stddev is not empty

* Removing trailing whitespaces

* scope _dp* variables

* fix whitespaces

modules/calib3d/src/calibration.cpp

@@ -1520,10 +1520,6 @@ static double cvCalibrateCamera2Internal( const CvMat* objectPoints,
     nparams = NINTRINSIC + nimages*6;
     if( releaseObject )
         nparams += maxPoints * 3;
-    Mat _Ji( maxPoints*2, NINTRINSIC, CV_64FC1, Scalar(0));
-    Mat _Je( maxPoints*2, 6, CV_64FC1 );
-    Mat _Jo( maxPoints*2, maxPoints*3, CV_64FC1, Scalar(0) );
-    Mat _err( maxPoints*2, 1, CV_64FC1 );
 
     _k = cvMat( distCoeffs->rows, distCoeffs->cols, CV_MAKETYPE(CV_64F,CV_MAT_CN(distCoeffs->type)), k);
     if( distCoeffs->rows*distCoeffs->cols*CV_MAT_CN(distCoeffs->type) < 8 )
@@ -1587,6 +1583,13 @@ static double cvCalibrateCamera2Internal( const CvMat* objectPoints,
 
     CvLevMarq solver( nparams, 0, termCrit );
 
+    Mat _Ji( maxPoints*2, NINTRINSIC, CV_64FC1, Scalar(0));
+    Mat _Je( maxPoints*2, 6, CV_64FC1 );
+    Mat _err( maxPoints*2, 1, CV_64FC1 );
+
+    const bool allocJo = (solver.state == CvLevMarq::CALC_J) || stdDevs;
+    Mat _Jo = allocJo ? Mat( maxPoints*2, maxPoints*3, CV_64FC1, Scalar(0) ) : Mat();
+
     if(flags & CALIB_USE_LU) {
         solver.solveMethod = DECOMP_LU;
     }
@@ -1720,20 +1723,22 @@ static double cvCalibrateCamera2Internal( const CvMat* objectPoints,
 
             _Je.resize(ni*2); _Ji.resize(ni*2); _err.resize(ni*2);
             _Jo.resize(ni*2);
+
+            CvMat _mp = cvMat(_err.reshape(2, 1));
+
+            if( calcJ )
+            {
                 CvMat _dpdr = cvMat(_Je.colRange(0, 3));
                 CvMat _dpdt = cvMat(_Je.colRange(3, 6));
                 CvMat _dpdf = cvMat(_Ji.colRange(0, 2));
                 CvMat _dpdc = cvMat(_Ji.colRange(2, 4));
                 CvMat _dpdk = cvMat(_Ji.colRange(4, NINTRINSIC));
-            CvMat _dpdo = cvMat(_Jo.colRange(0, ni * 3));
-            CvMat _mp = cvMat(_err.reshape(2, 1));
+                CvMat _dpdo = _Jo.empty() ? CvMat() : cvMat(_Jo.colRange(0, ni * 3));
 
-            if( calcJ )
-            {
                 cvProjectPoints2Internal( &_Mi, &_ri, &_ti, &matA, &_k, &_mp, &_dpdr, &_dpdt,
-                                  (flags & CALIB_FIX_FOCAL_LENGTH) ? 0 : &_dpdf,
-                                  (flags & CALIB_FIX_PRINCIPAL_POINT) ? 0 : &_dpdc, &_dpdk,
-                                  &_dpdo,
+                                  (flags & CALIB_FIX_FOCAL_LENGTH) ? nullptr : &_dpdf,
+                                  (flags & CALIB_FIX_PRINCIPAL_POINT) ? nullptr : &_dpdc, &_dpdk,
+                                  (_Jo.empty()) ? nullptr: &_dpdo,
                                   (flags & CALIB_FIX_ASPECT_RATIO) ? aspectRatio : 0);
             }
             else