Practical image hiding method using a phase wrapping rule and real-valued decoding key

We propose a practical image hiding method using phase wrapping and real-valued decoding key. A zero-padded original image, multiplied with a random-phase pattern, is Fourier transformed and its real-valued data denotes an encoded image in the embedding process. The encoded image is divided into two phase-encoded random patterns which are generated based on the phase wrapping rule. The imaginary part and the real part of these phase-encoded random patterns are used as a hidden image and a decoding key, respectively. A host image is then made from the linear superposition of the weighted hidden image and a cover image. The original image is simply obtained by the inverse-Fourier transform of the product of the host image and the decoding key in the reconstruction process. The embedding process and the reconstruction process are performed digitally and optically, respectively. Computer simulation and an optical experiment are shown in support of the proposed method.     

Encrypting image by assembling the fractal-image addition method and the binary encoding method

The fractal-image addition method and the binary encoding method are assembled to form a hybrid method for encrypting a digital covert image. For this hybrid method, a host image is used to create an overt image with the information of the covert image. First, the fractal-image addition method is used to add some fractal images and the covert image to form an image-mixing matrix. Then, all the pixel values of the image-mixing matrix are transferred into binary data. Finally, the binary data are encoded into the host image to create an overt image. The pixels of the overt image contain eight groups of codes used for reconstructing the covert image. The eight groups of codes are identification codes, row amount codes, covert-image dimension codes, fractal-image amount codes, starting-pixel codes, character amount codes, character codes, and information codes. The overt image and the host image look almost the same for eyes. Furthermore, the covert image can be directly reconstructed from the overt image without using the host image. The most important feature is that the reconstructed covert image is identical to the original covert image, i.e. there is no distortion in the decoding work.     

Hybrid encoding method by assembling the magic-matrix scrambling method and the binary encoding method in image hiding

The magic-matrix scrambling method and the binary encoding method are combined to form a hybrid encoding method for hiding digital covert images. For this hybrid encoding method, a covert image is encoded into a host image to form an overt image. First, the magic-matrix scrambling method is used to rearrange all the pixels of the covert image by using a specified magic matrix modified from a magic square to form a scrambled matrix. Then, all the pixels of the scrambled matrix are denoted by binary data. Finally, the binary data are encoded into the host image to form the overt image. The pixels of the overt image contain nine groups of codes used for decoding the covert image, i.e. identification codes, covert-image dimension codes, scrambling-time codes, magic-square dimension codes, corner codes, shifting codes, arrangement codes, graylevel codes, and information codes. The overt image and the host image look almost the same for eyes. Furthermore, the covert image can be decoded directly from the overt image without using the host image. The most important feature is that the decoded covert image is identical to the original covert image, i.e. there is no distortion in the decoding work.     

像素随机映射的快速算法及在LSB隐藏技术中的应用

提出一种像素随机映射的快速方法, 将该方法与像素字节低位隐藏信息的LSB(Least Significant Bit)技术相结合, 讨论了将RGB彩色图像作为载体隐匿真彩色图像、灰度图像、二值图像及全息信息的方法. 研究结果表明, 该方法加密及解密效率高, 载体图像具有较好的抗破译及抗剪切能力. 根据隐藏信息的性质合理使用LSB技术, 能在基本不影响载体图像质量的情况下较好地隐匿多种信息.     

一种新的可逆二维混沌映射图像加密算法

提出了一种用于图像加密的可逆二维混沌映射,该映射由左映射和右映射两个子映射组成。通过对图像的拉伸和折叠处理,实现了图像的混沌加密。首先沿图像的对角线方向将正方形图分为上下两个部分并重新组合成一个平行四边形的图像;然后利用平行四边形图像的两列像素之间的像素数目差将某列中的像素插入到相邻下一列像素之间。经过这样的过程,原始图像拉伸成为一条直线。最后按照原始图像的大小将这条直线折叠成为一个新的图像。推导出了映射的数学表达式,设计了密钥产生的方法,分析了图像加密算法的安全性问题。仿真验证了该图像加密算法的有效性。     

Image super-resolution based on local self-similarity

A new image super-resolution method based on a codebook mapping is proposed. The codebook mapping represents the internal relationship between low-and high-frequency image components, and is used for the estimation of highfrequency image components lost in the sampling process. In the proposed method, codebooks are first generated by the low-and high-frequency image components of the original image itself that is to be processed. Then, a resultant superresolution image, that is, an enlarged image, is obtained by combining the estimated high-frequency image components with the low-frequency ones obtained by a typical interpolation-based method. The effectiveness of the proposed method is verified by comparing it against some conventional methods.     

A method for hiding information utilizing double-random phase-encoding technique

A method for hiding information is proposed. Firstly, the image to be hidden is encoded by the doubled-random phase-encoding technique. Then, the real part of the encoded data, together with the imaginary part, is embedded into a sufficiently large host image, which has been enlarged according to some rules. The superposition weighting is adjusted to a proper value such that the composed image will not be subject to severe degradation compared to the original host image. When decryption is needed, the reconstructed hidden image can be extracted directly from the composed image without using original host image, with the result being quite satisfactory. The quality of the reconstructed hidden image and of the composed image has been analyzed as the superposition weight varies, allowing the determination of the optimum superposition weight. The optimum superposition weight is related to the average gray level value of the hiding image.     

Optical imaging system with a waveguide

The problem of image transmission through a waveguide is considered. The transfer function of a step rectangular waveguide is obtained, and it is concluded that direct image transmission is possible over large distances without significant loss of quality. An optical system with a waveguide in which an image is formed with a single objective is proposed. The process of image transmission through a step planar dielectric waveguide is experimentally investigated, and the influence of parameters of the waveguide on the resulting image is revealed. The conditions for image transmission through waveguides of other types are discussed.     

Nonlocal regularization based on DT-CWT for WMSN video image iterative reconstruction

The prior knowledge of signal is the previous condition of image compressed sensing reconstruction. In order to improve the quality of the priors except for image sparsity, this paper proposes a new model of video image reconstruction. The texture is the important visual feature of video image as a result of its repeat, leading to image global geometrical structures. The nonlocal idea comes from image self-familiar and can represent image detail features from the geometrical point of view. Therefore, the texture geometrical feature of video image is researched, and we take advantage of dual-tree complex wavelet transform to portray the sparsity representation regularization of the texture. What is more, global constrained regularization is constructed with the help of the nonlocal idea. On the basis of the two regularizations above, a new reconstruction model of video image compressed sensing is proposed, which not only preserves the sparsity prior knowledge of image but also improves the quality of prior knowledge of image by promoting geometrical structure. Iterative shrinkage thresholding algorithm is adopted to solve the model leading to a both simple and quick iterative algorithm. Numerical experiments show that our method is efficient for video image recovery, especially preserving the global details of the original video image.     

基于多尺度形态学滤波器的图像融合新方法

提出了一种保持图像细节和高抗噪性的图像融合新方法。这种方法首先对源图像进行多尺度形态学开闭滤波,得到源图像的低频平滑图像;然后应用多尺度Top-hat变换和Bottom-hat变换来提取小于相应尺度的图像细节特征。因为在较小的尺度特征中包含噪声颗粒的可能性较大,据此修正了Top-hat变换和Bottom-hat变换的相应系数;最后对以上两步骤得到的低频平滑图像和多尺度高频细节图像分别进行图像融合,应用形态学重建过程生成融合图像。实验表明,这种融合方法具有图像细节保持完整和噪声消除效果好的优点,处理效果优于传统的图像融合方法。     

ARM架构下计算机图像并行化处理技术研究

为在图像处理与分析时具备良好的视觉效果,提高图像处理的速度,需要对ARM架构下计算机图像并行化处理技术进行研究。当前采用的方法是对各种变换频域图像特征提取与计算机图像集合特征的提取进行相结合,克服了当前对图像进行提取时存在图像形状描述的缺陷,提取图像特征向量维数相对较低。实验表明,通过对图像进行特征提取能很好的对图像效果进行展示,将图像的纹理特征进行详细的表述,将该方法应用到图像处理技术当中,具有良好的去噪效果及扩展性,该方法过程简单,但存在图像视觉效果较差的问题。为此,提出一种ARM架构下计算机图像并行化处理技术研究方法。该方法首先利用非局部均值去噪算法对图像进行去噪处理,然后结合图像去噪的结果利用小波变换对去噪图像进行边缘检测,最后采用非线性增强算法对图像进行增强完成对ARM架构下计算机图像并行化处理技术研究。实验结果表明,所提方法不仅提高图像处理速度,还提高图像视觉效果,具有广泛的应用价值。     

像增强器的荧光屏亮度均匀性测试的校正法研究

像增强器荧光屏亮度均匀性参数是判断其性能好坏的一个重要技术指标。设计了一种测试系统来测试它的亮度均匀性参数。该系统利用标定过的具有均匀亮度的荧光屏(裸屏),以标准像增强器的图像作为标准来校正面源电子枪。由于校正后的面源电子枪仍然存在误差,所以具有均匀亮度的荧光屏(裸屏)的图像不可能是完全均匀的,呈现边缘暗中间亮。分析其图像的亮度曲线,建立校正函数,改变校正函数中的调节系数,直到计算机上显示出图像均匀为止,这时可得出系数确定的校正函数。首先利用校正后的电子枪轰击待测荧光屏,采集其图像,以确定的校正函数对其进行修正,然后观察由计算机显示出的图像是否均匀,从而判断待测荧光屏的均匀性。     

多帧距离选通图像点扩散函数估计的超分辨率重建

为了解决水下激光距离选通图像成像过程中退化模型复杂的难题,提出了利用连续帧图像估计点扩散函数的距离选通超分辨成像方法。首先,从连续帧图像中选取一帧为参考帧作为初始清晰图像,下一帧图像为模糊图像,用梯度约束的方法求出点扩散函数,用于优化清晰图像;然后,依次将后续帧图像当作模糊图像与清晰图像交替迭代求取点扩散函数并优化更新清晰图像;最后获得的清晰图像与参考帧图像用乘法更新的方法估计点扩散函数,结合凸集投影法算法进行超分辨率成像重建。仿真实验结果表明,改进的算法重建图像分辨率和质量明显优于原始的算法。     

Physical consideration of an image in image restoration using Bayes’ formula

We consider image restoration by Bayes’ formula and investigate the relationship between an image and a prior probability from the following two viewpoints: hyperparameter estimation and the accuracy of a restored image. The Q-Ising model is adopted as a prior probability in Bayes’ formula. Not the Q-Ising energy, but the Potts energy plays an important role in the hyperparameter estimation. From the viewpoint of the hyperparameter estimation, the relationship between a natural image and a prior probability is characterized through the Potts energy and magnetization of an image. The Potts energy and magnetization of an image are defined by a set of pixels’ state of an image. The closer to the average Potts energy and magnetization over a prior probability the Potts energy and magnetization of a natural image is, the closer to the true value of a hyperparameter the estimated value of a hyperparameter from a degraded image is. For the accuracy of a restored image, the image which has a smaller Q-Ising energy is better restored by Bayes’ formula composed of the Q-Ising prior. The consideration for the relationship between an image and a prior probability is expected to be valid for a more complicated prior probability.     

一种基于信息理论的高动态范围图像评价方法

高动态范围图像(high dynamic range image)指的是扩大了景物可分辨的光照范围的图像。在HDRI成像中动态范围是难以量化测量的,必须将对动态范围的计算转化为其它易于计算的像质评价函数。HDRI图像的像质评价和普通图像的像质评价存在着较大不同。比较了几种像质评价的方法后,提出了利用图像的熵作为标准进行高动态范围成像评价的方法。利用一种自然图像的概率模型对图像的熵与成像动态范围之间的关系进行了数值模拟,得到了具有普遍意义上的理想成像动态范围的计算公式,公式指出了对自然景物完善成像所需的最大动态范围;给出了图像熵与动态范围之间的关系。利用这种关系可以经由计算图像的熵来对系统的动态范围特性做出评价。这种评价方法在指导高动态范围成像系统的设计,以及高动态范围成像系统的测试中将发挥重要的作用。     

Experimental observation of image sticking phenomenon in AC plasma display panel

The itinerant strong sustain discharge that occurs during a sustain period over a few minutes causes image sticking, which means a ghost image remains in the subsequent image when the previous image was continuously displayed over a few minutes. Accordingly, this paper investigates whether the dominant factor in image sticking is the MgO surface or phosphor layer by testing the effects of image sticking in subsequent dark and bright images using a 42-in plasma display panel. When the subsequent image was dark, the image sticking was found to produce a brighter ghost image than the background. Thus, since the luminance of a dark image is produced by the weak discharge that occurs during the reset-period, the higher luminance of the ghost image was mainly due to the activation of the MgO surface. Conversely, when the subsequent image was bright, the image sticking was found to produce a darker ghost image than the background. Thus, since the luminance of a bright image is predominantly produced by the strong discharge that occurs during the sustain period, the lower luminance of the ghost image was mainly due to the deterioration of the phosphor layer.     

噪声对数字图像相关法计算结果的影响研究

不同的散斑场会显示出不同的灰度分布特征,并对数字图像相关方法的计算结果有着重要影响。使用计算机模拟生成一系列单向拉伸图像和双向拉伸图像,并在生成的图像中添加噪声,从而获得一系列含噪声单向拉伸图像和含噪声双向拉伸图像。使用数字图像相关方法对无噪声图像和含噪声图像分别进行相关计算,并分析研究图像应变量与相关计算结果正确率间的关系,研究结果表明发现当图像的应变量在一定范围内时,数字图像相关方法计算结果的正确率较高。同时发现,当图像的应变量较小时,噪声对相关计算结果的影响较大,随着图像应变量的增大,噪声对相关计算结果的影响逐渐减小,当图像的应变量到达一定程度时,噪声对相关计算的影响就不明显了。     

A novel cellular automata based technique for visual multimedia content encryption

This paper proposes a new method for visual multimedia content encryption using Cellular Automata (CA). The encryption scheme is based on the application of an attribute of the CLF XOR filter, according to which the original content of a cellular neighborhood can be reconstructed following a predetermined number of repeated applications of the filter.The encryption is achieved using a key image of the same dimensions as the image being encrypted. This technique is accompanied by the one-time pad (OTP) encryption method, rendering the proposed method reasonably powerful, given the very large number of resultant potential security keys. The method presented here makes encryption possible in cases where there is more than one image with the use of just one key image. A further significant characteristic of the proposed method is that it demonstrates how techniques from the field of image retrieval can be used in the field of image encryption. The proposed method is further strengthened by the fact that the resulting encrypted image for a given key image is different each time. The encryption result depends on the structure of an artificial image produced by the superposition of four 1-D CA time-space diagrams as well as from a CA random number generator.A semi-blind source separation algorithm is used to decrypt the encrypted image. The result of the decryption is a lossless representation of the encrypted image. Simulation results demonstrate the effectiveness of the proposed encryption method. The proposed method is implemented in C# and is available online through the img(Rummager) application.     

相干激光雷达距离像的噪声抑制算法研究

激光雷达能同时成距离像和强度像,较其他的成像体制给出更多的有用信息。距离像的去噪是激光雷达图像处理的关键步骤,去噪的好坏直接关系激光雷达在跟踪、定位等方面的精确性。根据距离像噪声来源,采用结合强度像的多级中值滤波对实际的雷达图像进行了去噪处理。首先利用强度像3×3邻域均值和图像平均值消除失落信息影响,然后采用多级中值滤波消除逸出值。分别给出了各步处理结果,最终获得了较清晰的距离像。研究结果表明运用结合强度像的多级中值滤波方法能够有效地抑制相干激光雷达距离像的噪声。     

基于YCbCr颜色空间的Retinex低照度图像增强方法研究

针对Retinex理论的低照度图像增强算法中光照图像估计问题,提出一种基于YCbCr颜色空间的低照度图像增强方法.该方法将原始低照度图像从RGB(Red Green Blue)颜色空间转换到YCbCr颜色空间,提取该空间中Y分量构建为原始光照图像分量L1(x,y),并对L1(x,y)进行Gamma校正得到增强的光照图像分量L2(x,y),经Retinex模型得到增强图像R(x,y),采用多尺度细节增强方法对图像R(x,y)进行细节增强,得到最终增强图像Re(x,y).实验结果表明,所提方法不仅能有效提升亮度,避免亮度和色彩失真,增强了图像的细节信息并获得了更好的视觉效果,而且运行速度快.