COCO-Stuff: Thing and Stuff Classes in Context

TL;DR

COCO-Stuff enhances the COCO dataset with detailed pixel-wise annotations for 91 stuff classes, enabling better understanding of scene context, object relationships, and segmentation performance analysis.

Contribution

The paper introduces COCO-Stuff, a large-scale dataset with pixel-wise annotations for stuff classes, and presents an annotation protocol and analysis of scene context and segmentation.

Findings

Stuff classes cover significant image surface area.

Rich spatial relations between stuff and things are identified.

Segmentation performance varies between stuff and thing classes.

Abstract

Semantic classes can be either things (objects with a well-defined shape, e.g. car, person) or stuff (amorphous background regions, e.g. grass, sky). While lots of classification and detection works focus on thing classes, less attention has been given to stuff classes. Nonetheless, stuff classes are important as they allow to explain important aspects of an image, including (1) scene type; (2) which thing classes are likely to be present and their location (through contextual reasoning); (3) physical attributes, material types and geometric properties of the scene. To understand stuff and things in context we introduce COCO-Stuff, which augments all 164K images of the COCO 2017 dataset with pixel-wise annotations for 91 stuff classes. We introduce an efficient stuff annotation protocol based on superpixels, which leverages the original thing annotations. We quantify the speed versus quality trade-off of our protocol and explore the relation between annotation time and boundary complexity. Furthermore, we use COCO-Stuff to analyze: (a) the importance of stuff and thing classes in terms of their surface cover and how frequently they are mentioned in image captions; (b) the spatial relations between stuff and things, highlighting the rich contextual relations that make our dataset unique; (c) the performance of a modern semantic segmentation method on stuff and thing classes, and whether stuff is easier to segment than things.