Deep image steganography (DIS) has achieved significant results in capacity and invisibility. However, current paradigms enforce the secret image to maintain the same resolution as the cover image during hiding and revealing. This leads to two challenges: secret images with inconsistent resolutions must undergo resampling beforehand which results in detail loss during recovery, and the secret image cannot be recovered to its original resolution when the resolution value is unknown. To address these, we propose ARDIS, the first Arbitrary Resolution DIS framework, which shifts the paradigm from discrete mapping to reference-guided continuous signal reconstruction. Specifically, to minimize the detail loss caused by resolution mismatch, we first design a Frequency Decoupling Architecture in hiding stage. It disentangles the secret into a resolution-aligned global basis and a resolution-agnostic high-frequency latent to hide in a fixed-resolution cover. Second, for recovery, we propose a Latent-Guided Implicit Reconstructor to perform deterministic restoration. The recovered detail latent code modulates a continuous implicit function to accurately query and render high-frequency residuals onto the recovered global basis, ensuring faithful restoration of original details. Furthermore, to achieve blind recovery, we introduce an Implicit Resolution Coding strategy. By transforming discrete resolution values into dense feature maps and hiding them in the redundant space of the feature domain, the reconstructor can correctly decode the secret's resolution directly from the steganographic representation. Experimental results demonstrate that ARDIS significantly outperforms state-of-the-art methods in both invisibility and cross-resolution recovery fidelity.

翻译：深度图像隐写（DIS）在容量与不可感知性方面已取得显著成果。然而，现有范式强制要求秘密图像在隐藏与提取阶段保持与载体图像相同的分辨率。这导致两个挑战：分辨率不一致的秘密图像必须预先进行重采样，导致恢复过程中的细节损失；且当分辨率值未知时，秘密图像无法恢复至其原始分辨率。为解决这些问题，我们提出了ARDIS——首个任意分辨率深度图像隐写框架，该框架将范式从离散映射转向参考引导的连续信号重建。具体而言，为最小化由分辨率失配引起的细节损失，我们首先在隐藏阶段设计了一种频率解耦架构。该架构将秘密图像解耦为分辨率对齐的全局基频分量与分辨率无关的高频潜在编码，并将其隐藏于固定分辨率的载体中。其次，在恢复阶段，我们提出了一种潜在编码引导的隐式重建器以执行确定性复原。恢复出的细节潜在编码调制一个连续隐式函数，从而精确查询高频残差并将其渲染至恢复的全局基频分量上，确保原始细节的忠实还原。此外，为实现盲恢复，我们引入了一种隐式分辨率编码策略。通过将离散分辨率值转换为稠密特征图，并将其隐藏于特征域的冗余空间中，重建器能够直接从隐写表示中正确解码出秘密图像的分辨率。实验结果表明，ARDIS在不可感知性与跨分辨率恢复保真度方面均显著优于现有最先进方法。