One Patch to Caption Them All: A Unified Zero-Shot Captioning Framework
Authors: name: Lorenzo Bianchi; name: Giacomo Pacini; name: Fabio Carrara; name: Nicola Messina; name: Giuseppe Amato; name: Fabrizio Falchi
Published: 2025-10-03 11:05:56

Abstract: Zero-shot captioners are recently proposed models that utilize common-space
vision-language representations to caption images without relying on paired
image-text data. To caption an image, they proceed by textually decoding a
text-aligned image feature, but they limit their scope to global
representations and whole-image captions. We present , a
unified framework for zero-shot captioning that shifts from an image-centric to
a patch-centric paradigm, enabling the captioning of arbitrary regions without
the need of region-level supervision. Instead of relying on global image
representations, we treat individual patches as atomic captioning units and
aggregate them to describe arbitrary regions, from single patches to
non-contiguous areas and entire images. We analyze the key ingredients that
enable current latent captioners to work in our novel proposed framework.
Experiments demonstrate that backbones producing meaningful, dense visual
features, such as DINO, are key to achieving state-of-the-art performance in
multiple region-based captioning tasks. Compared to other baselines and
state-of-the-art competitors, our models achieve better performance on
zero-shot dense, region-set, and a newly introduced trace captioning task,
highlighting the effectiveness of patch-wise semantic representations for
scalable caption generation. Project page at https://paciosoft.com/Patch-ioner/ .