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Unification of Semantic and Instance Segmentation with BoundaryX

Open Access
|Sep 2025

Abstract

Semantic segmentation is a field of image content recognition in which each pixel is classified according to the type of object it belongs to, while instance segmentation distinguishes individual object instances. A novel method, BoundaryX, is proposed to unify both tasks without relying on bounding boxes. Each pixel is classified, and boundaries are drawn around separate instances, enabling easy bounding box calculation without shape constraints or region proposals. Both instanced objects (like people) and non-instanced ones (like the sky) are handled by BoundaryX, without hardcoded exceptions. The quality of the method was evaluated on the COCO dataset for the class “people” by measuring Intersection over Union (IoU) for the semantic segmentation and bounding boxes recall and precision. The method achieved 0.774 IoU for semantic segmentation, 75% recall, and 83% precision for bounding box quality. Segmentation pipelines are simplified through the unified solution and flexible boundary-based representation provided by BoundaryX.

DOI: https://doi.org/10.2478/cait-2025-0022 | Journal eISSN: 1314-4081 | Journal ISSN: 1311-9702
Language: English
Page range: 54 - 67
Submitted on: May 13, 2025
Accepted on: Sep 4, 2025
Published on: Sep 25, 2025
Published by: Bulgarian Academy of Sciences, Institute of Information and Communication Technologies
In partnership with: Paradigm Publishing Services
Publication frequency: 4 times per year

© 2025 Teodor Boyadzhiev, Krassimira Ivanova, published by Bulgarian Academy of Sciences, Institute of Information and Communication Technologies
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.