In this paper, a halftoning-based watermarking scheme with high data capacity and image quality is presented. Three types of watermarks of various pixel-depths, including 1-bit, 2-bit, and 3-bit, are able to be embedded without prominently damaging the image quality. To achieve high marked image quality, the parallel-oriented high efficient Direct Binary Search (DBS) halftoning is adopted to cooperate with the proposed Orientation Modulation (OM) method. In the decoder, the Least-Mean-Square-trained (LMS-trained) filters are adopted to extract the features of marked images in the frequency domain, and the naïve Bayes classifier is employed to analyze the extracted features and further decode the watermark information. Experimental results demonstrate that the proposed DBS-based OM encoding scheme provides excellent image quality, high processing efficiency, and high robustness to adapt to practical printing application.

In this paper, a halftoning-based watermarking method is presented. This method enables high pixel-depth watermark embedding, while maintaining high image quality. This technique is capable of embedding watermarks with pixel depths up to 3 bits without causing prominent degradation to the image quality. To achieve high image quality, the parallel oriented high-efficient direct binary search (DBS) halftoning is selected to be integrated with the proposed orientation modulation (OM) method. The OM method utilizes different halftone texture orientations to carry different watermark data. In the decoder, the least-mean-square-trained filters are applied for feature extraction from watermarked images in the frequency domain, and the naïve Bayes classifier is used to analyze the extracted features and ultimately to decode the watermark data. Experimental results show that the DBS-based OM encoding method maintains a high degree of image quality and realizes the processing efficiency and robustness to be adapted in printing applications.

Block truncation coding (BTC) has been considered as an efficient compression technique for decades. However, the annoying blocking effect and false contour caused by low bit rate configuration are key problems. To solve these problems, many former halftoning-based BTCs are proposed. However, these schemes also induce another impulse noise issue while the previous issues still have room for improvement. To cope with this, the iteration-based halftoning is combined with BTC, namely Direct-Binary-Search BTC (DBSBTC) to solve the aforementioned problems. Moreover, the high-speed DBS halftoning method along with the block-based strategy yield even faster processing speed than some of the former halftoning-based BTC schemes. As documented in the experimental results, the proposed DBSBTC is superior to the former halftoning-base BTC schemes in terms of image quality, and which makes the former schemes as potential candidates for surveillance and computer vision applications.

The transmitter output of OFDM or DMT systems with a rectangular window is known to have large spectral sidelobes. Windowing and pulse shaping have been proposed to reduce spectral leakage in the literature. If no extra cyclic prefix is available, windowing at the transmitter requires additional post-processing equalization at the receiver. In this paper, we design optimal windows with minimum spectral leakage. Moreover, we show that the post processing affects the SNR at the receiver and the resulting SNR can be given in a closed form. Furthermore, we demonstrate that we can have a good trade-off between SNR and spectral leakage.