Towards Simultaneous Image Compression and Indexing for Scalable Content-Based Retrieval in Remote Sensing

Due to the rapidly growing remote-sensing (RS) image archives, images are usually stored in a compressed format for reducing their storage sizes. Thus, most of the existing content-based RS image retrieval systems require fully decoding images (i.e., decompression) that is computationally demanding for large-scale archives. To address this issue, we introduce a novel approach devoted to simultaneous RS image compression and indexing for scalable content-based image retrieval (denoted as SCI-CBIR). The proposed SCI-CBIR prevents the requirement of decoding RS images before image search and retrieval. To this end, it includes two main steps: 1) deep-learning-based compression and 2) deep-hashing-based indexing. The first step effectively compresses RS images by employing a pair of deep encoder and decoder neural networks and an entropy model. The second step produces hash codes with a high discrimination capability for RS images by employing pairwise, bit-balancing, and classification loss functions. For the training of the SCI-CBIR approach, we also introduce a novel multistage learning procedure with automatic loss weighting techniques to characterize RS image representations that are appropriate for both RS image indexing and compression. The proposed learning procedure enables automatically weighting different loss functions considered for the proposed approach instead of computationally demanding grid search. Experimental results show the effectiveness of the proposed approach when compared to widely used approaches in RS. The code of the proposed approach is available at https://git.tu-berlin.de/rsim/SCI-CBIR.