OCCAM: Class-Agnostic, Training-Free, Prior-Free and Multi-Class Object Counting

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Hauptverfasser: Spanakis, Michail, Oikonomidis, Iason, Argyros, Antonis
Format: Preprint
Veröffentlicht: 2026
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author Spanakis, Michail
Oikonomidis, Iason
Argyros, Antonis
author_facet Spanakis, Michail
Oikonomidis, Iason
Argyros, Antonis
contents Class-Agnostic object Counting (CAC) involves counting instances of objects from arbitrary classes within an image. Due to its practical importance, CAC has received increasing attention in recent years. Most existing methods assume a single object class per image, rely on extensive training of large deep learning models and address the problem by incorporating additional information, such as visual exemplars or text prompts. In this paper, we present OCCAM, the first training-free approach to CAC that operates without the need of any supplementary information. Moreover, our approach addresses the multi-class variant of the problem, as it is capable of counting the object instances in each and every class among arbitrary object classes within an image. We leverage Segment Anything Model 2 (SAM2), a foundation model, and a custom threshold-based variant of the First Integer Neighbor Clustering Hierarchy (FINCH) algorithm to achieve competitive performance on widely used benchmark datasets, FSC-147 and CARPK. We propose a synthetic multi-class dataset and F1 score as a more suitable evaluation metric. The code for our method and the proposed synthetic dataset will be made publicly available at https://mikespanak.github.io/OCCAM_counter.
format Preprint
id arxiv_https___arxiv_org_abs_2601_13871
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle OCCAM: Class-Agnostic, Training-Free, Prior-Free and Multi-Class Object Counting
Spanakis, Michail
Oikonomidis, Iason
Argyros, Antonis
Computer Vision and Pattern Recognition
Class-Agnostic object Counting (CAC) involves counting instances of objects from arbitrary classes within an image. Due to its practical importance, CAC has received increasing attention in recent years. Most existing methods assume a single object class per image, rely on extensive training of large deep learning models and address the problem by incorporating additional information, such as visual exemplars or text prompts. In this paper, we present OCCAM, the first training-free approach to CAC that operates without the need of any supplementary information. Moreover, our approach addresses the multi-class variant of the problem, as it is capable of counting the object instances in each and every class among arbitrary object classes within an image. We leverage Segment Anything Model 2 (SAM2), a foundation model, and a custom threshold-based variant of the First Integer Neighbor Clustering Hierarchy (FINCH) algorithm to achieve competitive performance on widely used benchmark datasets, FSC-147 and CARPK. We propose a synthetic multi-class dataset and F1 score as a more suitable evaluation metric. The code for our method and the proposed synthetic dataset will be made publicly available at https://mikespanak.github.io/OCCAM_counter.
title OCCAM: Class-Agnostic, Training-Free, Prior-Free and Multi-Class Object Counting
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2601.13871