Piyu Tsai

Reversible image hiding scheme using predictive coding and histogram shifting

In this paper, a reversible image hiding scheme based on histogram shifting for medical images is proposed. As we know, the histogram-based reversible data hiding is limited by the hiding capacity, which is influenced by the overhead of position information that has to be embedded in the host image. To solve this problem, the similarity of neighboring pixels in the images was explored by using the prediction technique and the residual histogram of the predicted errors of the host image was used to hide the secret data in the proposed scheme. In addition, the overlapping between peak and zero pairs was used to further increase the hiding capacity. According to the experimental results, a higher hiding capacity was obtained and a good quality stego-image was preserved in the proposed scheme. The hiding capacity provided by the proposed scheme was approximately three times that of the original histogram-based method. Compared to the histogram-based method, the quality of the stego-image improved about 1.5dB when the same amounts of secret data were embedded.

A color image watermarking scheme based on color quantization

Digital watermarking has been widely applied to solve copyright protection problems of digital media relating to illegal use or distribution. In the past few years, several gray-level image watermarking schemes have been proposed, but their application to color image watermarking schemes is scarce and usually works on the luminance or individual color channel. In this paper, a new color image watermarking scheme based on the color quantization technique is proposed. Experimental results are shown to demonstrate the validity of the proposed scheme. Furthermore, the proposed scheme can be applied to other multimedia applications that are based on the color quantization technique.

Using set partitioning in hierarchical trees to authenticate digital images

In this paper, we present a new image authentication scheme to verify the contents of multi-resolution digital images. The authentication message of a given image is generated based on the set partition in hierarchical trees (SPIHT) encoding. When the original authentication message and the SPIHT decoded message of the image to be authenticated are compared, the given image can then be authenticated. The size of the authentication message is adaptive and is determined according to the user requirement. The experimental results show that the proposed scheme can distinguish acceptable operations from malicious manipulations. Furthermore, the positions of tampered areas can be located accurately.

A progressive secret reveal system based on SPIHT image transmission

Abstract In this paper, a novel secret-revealing system is proposed. The proposed system directly embeds a secret message in an encoded cover image. The set partitioning in hierarchical trees (SPIHT) technique is employed to encode the cover image. The bit stream of a list of significant pixels encoded during the SPIHT encoding process is exploited to hide the secret message. The hiding capacity of each SPIHT encoding stage is determined according to the number of extracted significant coefficients. In addition, an adaptive embedding mechanism is designed to increase the hiding capacity with little loss of image quality. To sum up, three characteristics are achieved in this system. First, a secret message is directly embedded in a SPIHT-encoded cover image. Second, the compression rate of the cover image is adaptive. Third, the hidden secret message is extracted progressively during the SPIHT decoding process.

Steganography using overlapping codebook partition

A tradeoff between the hiding capacity of a cover image and the quality of a stego-image in steganographic schemes is inevitable. This paper presents overlapping codebook partitioning to challenge this tradeoff. The codewords in a codebook are grouped into sub-clusters, according to similarity. Any size sub-cluster is allowed; moreover, a sub-cluster is permitted to overlap with sub-clusters to increase hiding capacity without sacrificing image quality. As a result of this improved scheme, the hiding capacity of a cover image increases, whereas the quality of a stego-image stays the same.

An adaptive two-stage edge detection scheme for digital color images

An adaptive two-stage edge detection scheme for digital color images is proposed in this paper. In the first stage of this scheme, each three-dimensional color image is reduced to a one-dimensional gray-level image using the moment-preserving thresholding technique. Then, a new edge detection technique based on the block truncation coding scheme is introduced to detect the edge boundary in the second stage. The edge detection process makes use of the bit plane information of each BTC-encoded block to detect the edge boundary. The experimental results show that the performance of the detected edge image of the proposed scheme is as good as in Yangs scheme and in the Sobel operator. However, the computational cost consumed by the proposed scheme is less than that of Yangs scheme. In addition, the proposed scheme provides an adaptive edge quality decision mechanism. This mechanism can provide different edge images to meet various applications and the subjective evaluation. Moreover, this scheme locates the edge boundaries to the sub-pixel accuracy, which is an advantage to applications such as data hiding and image watermarking.

Tree Structure Based Data Hiding for Progressive Transmission Images

Progressive image transmission (PIT) is supported by several encoders such as SPIHT, JPEG2000 and so on. However, few of data hiding scheme for progressive transmission images is designed. In this paper, tree-structure-based data hiding for set partitioning in hierarchical trees (SPIHT) images is proposed. The bit stream of SPIHT multi-stage encoded was structured of tree. The secret image can be progressively embedded into SPIHT bit trees. Experimental results showed the progressive image data hiding is achieved. The secret image is progressively embedded/extracted in SPIHT encoded images. Furthermore, a higher hiding capacity was provided in an earlier encoding which helped the secret image to be identified earlier. Also, an adaptive hiding capacity could be developed by using different tree structures. In comparison with Tsai et al.s scheme, the proposed scheme had a higher hiding capacity and a better secret image quality.

Refined codebook for grayscale image coding based on vector quantization

Abstract. Vector quantization (VQ) is a commonly used technique for image compression. Typically, the common codebooks (CCBs) that are designed by using multiple training images are used in VQ. The CCBs are stored in the public websites such that their storage cost can be omitted. In addition to the CCBs, the private codebooks (PCBs) that are designed by using the image to be compressed can be used in VQ. However, calculating the bit rates (BRs) of VQ includes the storage cost of the PCBs. It is observed that some codewords in the CCB are not used in VQ. The codebook refinement process is designed to generate the refined codebook (RCB) based on the CCB of each image. To cut down the BRs, the lossless index coding process and the two-stage lossless coding process are employed to encode the index table and the RCB, respectively. Experimental results reveal that the proposed scheme (PS) achieves better image qualities than VQ with the CCBs. In addition, the PS requires less BRs than VQ with the PCBs.

Residual Histogram Shifting Technique Based on Cascading Prediction for Reversible Data Hiding

To reversibly embed the secret data into the host image, the histogram shifting (HS) technique was proposed by embedding 1-bit secret data into the pixels in the peak points. To improve the hiding capacity of the histogram shifting technique, the residual histogram shifting (RHS) technique had been proposed. The prediction errors in the peak points of the residual histogram are used to embed the secret data. To further improve the hiding capacity, an improved block-based residual histogram shifting technique is proposed in this paper. The cascading prediction mechanism is employed in the proposed technique to generate the prediction errors for each image block. Experimental results reveal that the proposed technique provides higher hiding capacity than HS and RHS while keeping good image qualities of the embedded images.