Watermarking is an effective solution for copyright protection and forensics tracking via hiding information into the image signal. Recently, spatial-embedding watermarking methods from different transform domain have been proposed rapidly and effectively protect the copyright of the color image. Compared to the individual frequency domain method, it has both advantages of spatial domain and frequency domain. Here, we proposed a novel spatial-embedding watermarking method based on an attended just noticeable difference (JND) model with color complexity, to achieve a good tradeoff between robustness and perceptual quality. In particular, at the spatial embedding level, the direct current (DC) coefficients are selected for embedding and the perceptual JND model is used to guide the amount of pixel modification to improve visual quality. Different from the previous JND model, we proposed an attended JND model that considers color complexity, which is more consistent of the human visual perception model. Compared with the other JND models, the proposed JND model is more suitable for the watermarking framework. Experimental results show that the proposed watermarking scheme has better performance than other existing watermarking schemes. This greatly benefits the practical implementations of the spatialembedding watermarking methods.

GaF 3 /InF 3 based oxyfluoride glasses 20GaF 3 -15InF 3 -10SnF 2 -15ZnF 2 -17CdF 2 -3P 2 O 5 -(20-x) PbF 2 -xErF 3 were obtained by melt quenching method. By appropriate heat treatment of the as-prepared glasses above, transparent glass-ceramics were obtained with the formation of tetragonal ZnF 2 and cubic ErGa 5 O 12 nanocrystals in the glass matrix confirmed by X-ray diffraction. Differential scanning calorimetry (DSC), transform infrared spectrum and up-conversion luminescence measurements excited at 980nm were performed on as-prepared glasses and glass-ceramics. The different effects of Er 3+ content on ΔT 1 (ΔT 1 = T x -T g ) and ΔT 2 (ΔT 2 = T p 2 -T p 1 ) suggest the best content is 0.1 ~ 1 mol.% for controllable crystallization. The intensity of green luminescence significantly increased in transparent glass-ceramic until the content of Er 3+ reaches at 2 mol.% compared to that in as-prepared, but it did not enhance linearly with the increasing time. These results are attributed to the change of environment of Er 3+ ions and the decrease distance when Er 3+ ions are incorporated into the precipitated nanocrystals.

A systematic investigation on glass formation in the 20GaF 3 -15InF 3 -20CdF 2 -15ZnF 2 -(20-x)PbF 2 -10SnF 2 -xZrO 2 (xZ-GICZPS) system (x = 0, 2, 4, 6, 8 in mol.%) was carried out. These glasses were characterized by differential scanning calorimetry (DSC), infrared (IR) spectra and Raman spectra. The DSC results show that the thermal stability is affected by PbF 2 and ZrO 2 contents. With increasing ZrO 2 content, the thermal stability is improved at first and then reduced, which is proved by thermal stability factors ΔT and S determined by DSC. As a result, the 20GaF 3 -15InF 3 -20CdF 2 -15ZnF 2 -14PbF 2 -10SnF 2 -6ZrO 2 glass shows the largest parameters ΔT and S, processing the most excellent thermal stability. Analyses of IR spectra reveal that glasses have broad transparency range in IR region. According to Raman spectra, the glass network structures are basically composed of mixed [(In, Ga)F 6 ] and In[O, F] 6 units and ZrO 2 mainly acts as network modifier in this system.

In the robust image watermarking framework, watermarks are usually embedded in the direct current (DC) coefficients in discrete cosine transform (DCT) domain, since the DC coefficients have a larger perceptual capacity than any alternating current (AC) coefficients. However, DC coefficients are also excluded from watermark embedding with the consideration of avoiding block artifacts in watermarked images. Studies on human vision suggest that perceptual characteristics can achieve better image fidelity. With this perspective, we propose a novel spatial–perceptual embedding for a color image watermarking algorithm that includes the robust just-noticeable difference (JND) guidance. The logarithmic transform function is used for quantization embedding. Meanwhile, an adaptive quantization step is modeled by incorporating the partial AC coefficients. The novelty and effectiveness of the proposed framework are supported by JND perceptual guidance for spatial pixels. Experiments validate that the proposed watermarking algorithm produces a significantly better performance.