Images are Worth Variable Length of Representations
Authors: name: Lingjun Mao, name: Rodolfo Corona, name: Xin Liang, name: Wenhao Yan, name: Zineng Tang

Most existing vision encoders map images into a fixed-length sequence of
tokens, overlooking the fact that different images contain varying amounts of
information. For example, a visually complex image (e.g., a cluttered room)
inherently carries more information and thus deserves more tokens than a simple
image (e.g., a blank wall). To address this inefficiency, we propose DOVE, a
dynamic vision encoder that produces a variable number of visual tokens (i.e.,
continuous representation vectors) to reconstruct each image. Our results show
that DOVE significantly reduces the average number of tokens while maintaining
high reconstruction quality. In several linear probing and downstream
multimodal tasks, it outperforms existing autoencoder-based tokenization
methods when using far fewer tokens, capturing more expressive semantic
features compared to fixed-length encoding. We further extend DOVE with
query-conditioned tokenization. By guiding the model to focus on query-relevant
regions, it achieves more efficient and targeted semantic extraction. Our code
and checkpoints are available at https://dove-encoder.github.io/dove-encoder.