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In this paper, a new scheme of reversible watermarking is proposed using a complementary embedding strategy in the spatial domain. The proposed scheme consists of two stages: horizontal direction embedding and vertical direction embedding. A complementary embedding strategy is designed to increase the embedding capacity and decrease the distortion of the watermarked image in the vertical direction embedding. Specifically, in the horizontal direction, the proposed scheme embeds one secret data bit by increasing values of pixels in even rows and decreasing values of pixels in odd rows by one. In the vertical direction, it embeds another secret data bit by decreasing values of pixels in even rows and increasing values of pixels in odd rows by one. In addition, a histogram shrinkage technique is adopted to prevent overflow and underflow problems. Experimental results demonstrate that the proposed reversible watermarking scheme outperforms state-of-the-art methods in terms of both embedding capacity and watermarked image quality.INDEX TERMS Complementary embedding strategy, prediction error, reversible watermarking.

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Image reversible data hiding (RDH) using interpolation technology (IT) provides high singlelayer embedding capacity and has become a research hotspot. To solve serious image distortion in existing methods caused by secondary embedding based on interpolated pixels, we propose an RDH method for interpolated images based on modulo operation and prediction-error expansion (PEE). Our method differs from existing RDH methods that only consider embedding data into interpolated pixels. First, an image interpolation method is used to generate an interpolated image, which is partitioned into overlapping 3 × 3 blocks. For each block, secret data are embedded into interpolated pixels using the modulo operation and into reference pixel using the PEE. Standard grayscale images of size 512 × 512 were selected from the popular BossBase and BOWS-2 image databases as input images for experiments. Extensive experimental results show that the proposed method avoids pixel values underflow/overflow caused by embedding data and reduces image distortion effectively. For each standard test image, the maximum bits per pixel (BPP) is higher than 1.5, and the corresponding peak signal to noise ratio (PSNR) is higher than 45.0 dB. At the given embedding capacity, the proposed method outperforms recent similar methods regarding the watermarked image quality. Moreover, the proposed method can resist histogram analysis, and the subjective evaluation proves that the proposed method has good imperceptibility.INDEX TERMS Reversible data hiding, interpolated image, modulo operation, prediction-error expansion.

In this paper, for color image copyright protection application, a new and blind color image watermarking algorithm based on quantitation method in three dimensional discrete cosine transform (3D-DCT) is proposed. Firstly, the original RGB color image is divided into non-overlapping blocks sized 8 × 8 × 3, and then performs 3D-DCT transform on each block. Secondly, embed a bit watermarking signal into each block's 3D-DCT direct-current (DC) coefficient by quantization method. The results show that the proposed scheme has very good imperceptibility and robustness against the common image processing attacks. Compared with similar algorithm, the proposed scheme has better robustness performance for most attacks.