## 1 Introduction  
With the rapid development of information technology, image encryption techniques have gained a high level of interest. In recent years, images have been maliciously modified or destroyed by criminals, which not only loses the original value of the image, but also may cause copyright disputes. Therefore, copyright protection for images is of great significance. Digital watermark is a kind of copyright protection technology [1], whose basic idea is to embed the copyright watermark logo in the carrier image by an embedding algorithm. When a copyright dispute occurs, the copyright holder can extract the copyright logo by watermark extraction algorithm, and then compare it with the registered watermark image in the copyright protection center to complete the copyright authentication process. Compared with traditional 2D images, 3D images have attracted more and more attention because of their stereoscopic nature, excellent experience and ability to truly reproduce life scenes. Integral imaging (InI) is a practical light-field [2] three-dimensional imaging method; it originated from the integral photography(IP) [3] proposed by [PERSON] in 1908 and has become one of the cutting-edge 3D display methods in the international arena. InI uses a microlens array (MLA) to capture a set of element images (EIs) [4]. Each element image shows an incoherent illuminated 3D scene of different perspectives. The InI system can obtain the direction and spatial information of the light ray from the scene [5] and project this information on a 2D display to produce a 3D image visible to the naked eye without any special glasses. There have been many research results on copyright protection of 2D images, and its watermarking algorithms can be implemented either by spatial domain algorithms or by frequency domain algorithms [6, 7]. In 2008, a digital museum copyright protection method based on the discrete wavelet transform (DWT) was proposed in [8],where the Fresnel hologram of the watermarked image is embedded in the protected object by the discrete wavelet transform (DWT). After watermark detection, the copyright information appears in the reconstructed hologram. In [9], the authors proposed discrete cosine transform (DCT) as a method for embedding watermarks with high accuracy in extracting watermarks, and it is less affected by image compression. In [10], the authors proposed a cellular automata (CA)-based watermarking method for copyright protection of 2D images with better results than the traditional transform methods (DWT, DFT, etc. )-based watermarking techniques. In 2019, [PERSON] and [PERSON] [11] proposed using a 3D CA filter to embed 3D watermark-converted data (QR codes) into cellular automata (CA) domains instead of 2D watermarks. This approach protects the copyright of holographic videos from malicious copying and is robust to noise and compression attacks. In 2020, [PERSON] et al. [12] proposed a robust watermarking scheme using different transformations (i.e., DWT, IWT and CT) and segmentation by block. In the embedding process, the image is segmented into uniform blocks and the blocks are transformed. Finally, the watermarked bits are embedded using the LL band. The method achieves significant invisibility results, but the robustness to various signal processing attacks needs to be improved. In 2021, [PERSON] and [PERSON] [13] proposed a method for protecting the ownership of light-field images based on high-dimensional color transform (HDCT) watermarking, which outperformed existing light-field watermarking algorithms in terms of both imperceptibility and robustness. [PERSON] [14] proposed a robust hybrid watermarking method based on discrete cosine transform (DCT), discrete wavelet transform (DWT) and scale invariant feature transform (SIFT). SIFT is used to protect the watermark from geometric attacks while the watermark is embedded in the DWT-DCT domain to resist image processing operations. Medical images contain a lot of patient information and have a high demand for privacy. In [15], [PERSON] et al.