Dynamic kernel-based adaptive spatial aggregation for learned image compression

Learned image compression methods have shown remarkable performance and expansion potential compared to traditional codecs. Currently, there are two mainstream image compression frameworks: one uses stacked convolution and other uses window-based self-attention for transform coding, most of which aggregate valuable dependencies in a fixed spatial range. In this paper, we focus on extending content-adaptive aggregation capability and propose a dynamic kernel-based transform coding. The proposed adaptive aggregation generates kernel offsets to capture valuable information with dynamic sampling convolution to help transform. With the adaptive aggregation strategy and the sharing weights mechanism, our method can achieve promising transform capability with acceptable model complexity. Besides, considering the coarse hyper prior, the channel-wise, and the spatial context, we formulate a generalized entropy model. Based on it, we introduce dynamic kernel in hyper-prior to generate more expressive side information context. Furthermore, we propose an asymmetric sparse entropy model according to the investigation of the spatial and variance characteristics of the grouped latents. The proposed entropy model can facilitate entropy coding to reduce statistical redundancy while maintaining inference efficiency. Experimental results demonstrate that our method achieves superior rate–distortion performance on three benchmarks compared to the state-of-the-art learning-based methods.