Merge pull request #29132 from hcy11123323:4.x

core: fix inverted continuity check in cvReshapeMatND() #29132

### Pull Request Readiness Checklist

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- [√] I agree to contribute to the project under Apache 2 License.
- [√] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [ ] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/core/src/array.cpp

@@ -2660,7 +2660,7 @@ cvReshapeMatND( const CvArr* arr,
                 mat = &stub;
             }
 
-            if( CV_IS_MAT_CONT( mat->type ))
+            if( !CV_IS_MAT_CONT( mat->type ))
                 CV_Error( cv::Error::StsBadArg, "Non-continuous nD arrays are not supported" );
 
             size1 = mat->dim[0].size;

modules/core/test/test_mat.cpp

@@ -2626,6 +2626,24 @@ TEST(Mat1D, DISABLED_basic)
     }
 }
 
+TEST(Mat, regression_cvReshapeMatND_continuous)
+{
+    int sizes[] = {2, 3, 4};
+    Mat mat(3, sizes, CV_32SC1);
+    CvMatND src = cvMatND(mat);
+    CvMatND reshaped;
+    int new_sizes[] = {4, 3, 2};
+    CvArr* result = 0;
+
+    ASSERT_NO_THROW(result = cvReshapeMatND(&src, sizeof(reshaped), &reshaped, 0, 3, new_sizes));
+    ASSERT_NE((CvArr*)0, result);
+    EXPECT_EQ(3, reshaped.dims);
+    EXPECT_EQ(new_sizes[0], reshaped.dim[0].size);
+    EXPECT_EQ(new_sizes[1], reshaped.dim[1].size);
+    EXPECT_EQ(new_sizes[2], reshaped.dim[2].size);
+    EXPECT_EQ(src.data.ptr, reshaped.data.ptr);
+}
+
 TEST(Mat, ptrVecni_20044)
 {
     Mat_<int> m(3,4); m << 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12;