Mei-Yi Wu

An iterative method of palette-based image steganography

This article presents a novel iterative method of palette-based image steganography that minimizes the RMS error between an original image and its stego-image. The proposed method is based on a palette modification scheme, which can iteratively embed one message bit into each pixel in a palette-based image. In each iteration, both the cost of removing an entry color in a palette and the benefit of generating a new one to replace it are calculated. If the maximal benefit exceeds the minimal cost, a entry color is replaced. Experimental results show that the proposed method remarkably reduces the distortion of the carrier images (stego-images) to other palette-based methods.

Reversible data-hiding method for palette-based images

This study proposes a novel reversible data-hiding method based on an iterative approach for palette-based images. In each iteration, the number of occurrences of palette color in the image is computed in order to identify the most and least frequently occurring colors in a palette for data hiding. Data are hidden by sacrificing the least frequent color and placing the most frequent color in its position in the palette to make a pair . After the most frequent color takes over the palette index of the least frequent color, two palette indices stand for the most frequent color. Therefore, one bit can be hidden in every pixel where the most frequent color occurs in the image. To make the host image reversible, the overhead information caused by sacrificing the least frequent color must be saved for image reconstruction. The performance of the proposed method is demonstrated on test images by showing the capacity and distortion. Several successful similar efforts have also been implemented for comparison. Experimental results indicate that the proposed method has a high embedding capacity and good marked-image quality.

Robust object-based watermarking scheme via shape self-similarity segmentation

This study proposes a new object-based watermarking scheme based on efficient self-similarity segmentation in the spatial domain for solving the synchronizing detection problem. The lengths and orientations of two principle axes of image objects were used for image normalization and shape segmentation. Watermarks then can be embedded into object images by adjusting the pixel intensities on each segmented region. Experimental results reveal that the proposed method effectively resists geometrical attacks without using the original image.

A new inverse halftoning method using reversible data hiding for halftone images

A new inverse halftoning algorithm based on reversible data hiding techniques for halftone images is proposed in this paper. The proposed scheme has the advantages of two commonly used methods, the lookup table (LUT) and Gaussian filtering methods. We embed a part of important LUT templates into a halftone image and restore the lossless image after these templates have been extracted. Then a hybrid method is performed to reconstruct a grayscale image from the halftone image. In the image reconstruction process, the halftone image is scanned pixel by pixel. If the scanned pattern surrounding a pixel appeared in the LUT templates, a gray value is directly predicted using the LUT value; otherwise, it is predicted using Gaussian filtering. Experimental results show that the reconstructed grayscale images using the proposed scheme own better quality than both the LUT and Gaussian filtering methods.

Object watermarking scheme based on resynchronization and shape subdivision

In practical use, objects in still images and videos are easy to misappropriate with handy image-processing tools and need to be pro- tected. However, the few proposals for object watermarking suffer from resynchronization problems. In this study, we develop an object-based watermarking method based on efficient segmentation using lines paral- lel and perpendicular to two principal axes in the spatial domain. A patch- like scheme is designed to embed and extract invisible watermarks. In contrast with the previous object-based watermarking schemes, extra information for resynchronization is not required to be stored in our method. Experimental results show the robustness of the proposed method against many kinds of geometrical attacks.

Data Hiding Scheme to Improve the Quality of Reconstructed Images for Inverse Halftoning

The objective of inverse halftone reconstruction is to convert halftone bilevel images into gray-level images with the minimum distortion, but there is no way to construct a perfect gray-scale image from a given halftone image. A reversible data hiding approach is proposed to improve the recovered image quality for halftone images. The proposed approach firstly computes the difference image between the predicted image using Gaussian filtering from a halftone image and the original gray-scale one. The difference image is then compressed and embedded into the halftone image using a reversible data hiding method. In the image reconstruction process, the marked halftone image is scanned to extract the embedded difference image. Finally, a better quality of reconstructed image will be generated by adding the extracted difference image to the predicted image using Gaussian filtering. Experimental results show that the proposed approach can efficiently improve the quality of reconstructed images for inverse halftoning.

A multimedia tool for english learning using text retrieval techniques on DVD subtitles

In this paper, a multimedia tool named Supplementary Multimedia Material Provider (SMMP) is proposed. To extract relevant sentences from subtitles of audiovisual, learners input keywords which enable that the sentence containing the target vocabulary repeatedly be exposed. The SMMP employs text retrieval techniques using vocabulary concept similarity measurement and followed by displaying the found sentences in various ways like text, audio and video clips. Since not every single movie covers the proper content for every viewer for the intention of learning. The SMMP also provides the lexical level and category statistical analysis for viewers. These analyses are very useful as the criteria for language learners in selecting appropriate movies as their learning materials.

A data hiding scheme to reconstruct missing blocks for JPEG image transmission

This paper presents a new approach for recovering blocks of missing data in the mobile radio environment. When block based compression algorithm such as JPEG are used as part of the wireless transmission process and such images are transmitted over fading channels, the noise effects will usually cause block missing or damaging. The proposed method is based on quantizing the difference of coefficients between two distinct blocks and carefully encoding and embedding them in the least significant bits of other blocks. The proposed scheme can recover high-quality JPEG images from the corresponding corrupted images up to a block loss rate of 20% without carrying any side information. Experimental results show the proposed method outperforms than the method of Shao et al.[1].

A method to improve the stego-image quality for Palette-based image steganography

This article presents a method of palette-based image steganography that minimizes the RMS error between an original image and its stego-image. The proposed method is based on a palette modification scheme, which can iteratively embed one message bit into each pixel in a palette-based image. In each iteration, both the cost of removing a entry color in a palette and the benefit of generating a new one to replace it are calculated. If the maximal benefit exceeds the minimal cost, an entry color is replaced. Experimental results show that the proposed method can remarkably reduce the distortion of the carrier images (stego-images) to other palette-based methods.