Merge pull request #27432 from dkurt:d.kurtaev/ipp_distTransform

Correct IPP distanceTransform results with single thread #27432

### Pull Request Readiness Checklist

resolves #24082

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] 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
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/imgproc/src/distransform.cpp

@@ -796,6 +796,22 @@ void cv::distanceTransform( InputArray _src, OutputArray _dst, OutputArray _labe
                     ippFree( pBuffer );
                     if (status>=0)
                     {
+                        // https://github.com/opencv/opencv/issues/24082
+                        // There is probably a rounding issue that leads to non-deterministic behavior
+                        // between runs on positions closer to zeros by x-axis in straight direction.
+                        // As a workaround, we detect the distances that expected to be exact
+                        // number of pixels and round manually.
+                        static const float correctionDiff = 1.0f / (1 << 11);
+                        for (int i = 0; i < dst.rows; ++i)
+                        {
+                            float* row = dst.ptr<float>(i);
+                            for (int j = 0; j < dst.cols; ++j)
+                            {
+                                float rounded = static_cast<float>(cvRound(row[j]));
+                                if (fabs(row[j] - rounded) <= correctionDiff)
+                                    row[j] = rounded;
+                            }
+                        }
                         CV_IMPL_ADD(CV_IMPL_IPP);
                         return;
                     }