Shipeng Liu Liang Zhao Dengfeng Chen CLICv2: Image Complexity Representation via Content Invariance Contrastive Learning. 2025 March abs/2503.06641 CoRR https://doi.org/10.48550/arXiv.2503.06641 db/journals/corr/corr2503.html#abs-2503-06641 streams/journals/corr