Fix typo bug in the calculation of some derivatives (dmxdt, dmydt, dmxdr, dmydr)…

Fix typo bug in the calculation of some derivatives (dmxdt, dmydt, dmxdr, dmydr) in cvProjectPoints2 function.

modules/calib3d/src/calibration.cpp

@@ -1078,9 +1078,9 @@ CV_IMPL void cvProjectPoints2( const CvMat* objectPoints,
                     double dicdist2_dt = -icdist2*icdist2*(k[5]*dr2dt + 2*k[6]*r2*dr2dt + 3*k[7]*r4*dr2dt);
                     double da1dt = 2*(x*dydt[j] + y*dxdt[j]);
                     double dmxdt = fx*(dxdt[j]*cdist*icdist2 + x*dcdist_dt*icdist2 + x*cdist*dicdist2_dt +
-                                       k[2]*da1dt + k[3]*(dr2dt + 2*x*dxdt[j]));
+                                       k[2]*da1dt + k[3]*(dr2dt + 4*x*dxdt[j]));
                     double dmydt = fy*(dydt[j]*cdist*icdist2 + y*dcdist_dt*icdist2 + y*cdist*dicdist2_dt +
-                                       k[2]*(dr2dt + 2*y*dydt[j]) + k[3]*da1dt);
+                                       k[2]*(dr2dt + 4*y*dydt[j]) + k[3]*da1dt);
                     dpdt_p[j] = dmxdt;
                     dpdt_p[dpdt_step+j] = dmydt;
                 }
@@ -1116,9 +1116,9 @@ CV_IMPL void cvProjectPoints2( const CvMat* objectPoints,
                     double dicdist2_dr = -icdist2*icdist2*(k[5]*dr2dr + 2*k[6]*r2*dr2dr + 3*k[7]*r4*dr2dr);
                     double da1dr = 2*(x*dydr + y*dxdr);
                     double dmxdr = fx*(dxdr*cdist*icdist2 + x*dcdist_dr*icdist2 + x*cdist*dicdist2_dr +
-                                       k[2]*da1dr + k[3]*(dr2dr + 2*x*dxdr));
+                                       k[2]*da1dr + k[3]*(dr2dr + 4*x*dxdr));
                     double dmydr = fy*(dydr*cdist*icdist2 + y*dcdist_dr*icdist2 + y*cdist*dicdist2_dr +
-                                       k[2]*(dr2dr + 2*y*dydr) + k[3]*da1dr);
+                                       k[2]*(dr2dr + 4*y*dydr) + k[3]*da1dr);
                     dpdr_p[j] = dmxdr;
                     dpdr_p[dpdr_step+j] = dmydr;
                 }