Title: Talking Points: Describing and Localizing Pixels
Primary area: applications to computer vision, audio, language, and other modalities
Keywords: Keypoint Description, Keypoint Localization, Pixel-Level Grounding, Reinforcement Learning, Vision-Language Model

Abstract: Vision-language models have achieved remarkable success in cross-modal understanding. Yet, these models remain limited to object-level or region-level grounding, lacking the capability for pixel-precise keypoint comprehension through natural language. We introduce a novel framework for pixel level grounding. The framework consists of two complementary components: a Point Descriptor that generates rich, contextual descriptions of individual keypoints, and a Point Localizer that regresses precise pixel coordinates from these descriptions. Unlike prior work that relies on templated prompts or keypoint names, our approach produces free-form, coarse-to-fine descriptions that situate keypoints within their visual context.
Since there is no available dataset to train such a system, we introduce LlamaPointInPart, a carefully curated dataset of 20K+ image-keypoint-description triplets synthesized from multiple vision-language models, capturing multi-scale information from scene-level context to visual features around the keypoint. 
For cross-category generalization, we optimize the Point Descriptor on AP-10K via GRPO, using the frozen Point Localizer as a reward model to produce descriptions that maximize localization accuracy.
To evaluate our results we establish a new evaluation protocol. Instead of comparing the text description produced by our method to the ground truth, we use the localizer to determine how close is the predicted point generated to the ground truth point.
Experiments demonstrate superior performance compared to baseline models on LlamaPointInPart. 
The bidirectional nature of our framework enables applications in both keypoint-guided image understanding and language-guided precise localization. Our dataset and code will be published upon publication.

TL;DR: A bidirectional framework: Point Descriptor generates natural language from pixels, Point Localizer regresses coordinates from descriptions. RL optimizes descriptions for improved localization accuracy.