An efficient adaptive arithmetic coding image compression technology

This paper proposes an efficient lossless image compression scheme for still images based on an adaptive arithmetic coding compression algorithm. The algorithm increases the image coding compression rate and ensures the quality of the decoded image combined with the adaptive probability model and predictive coding. The use of adaptive models for each encoded image block dynamically estimates the probability of the relevant image block. The decoded image block can accurately recover the encoded image according to the code book information. We adopt an adaptive arithmetic coding algorithm for image compression that greatly improves the image compression rate. The results show that it is an effective compression technology.     

Multiple-encoding retrieval for optical security

We propose a method for image encryption by multiple-step random phase encoding with an undercover multiplexing operation. The true image is stored in a multiple record we call encodegram; and then we can reconstruct it by the use of the appropriate random phase masks and a retrieval protocol. To increase the security of the true hidden image and confuse unauthorized receivers, we add to the encodegram an encoded fake image with different content. This fake image has only a small effect on the retrieval of the true hidden image, owing to the specific property of this protocol. In the decryption step, we can reveal the true image by applying the inverse protocol to two cyphertexts, one the encodegram containing the true image along with the fake image; and the other helping to get the random phase key to achieve the true image. Computer simulations verify the validity of this method for image encryption. Digital implementation of the method makes it particularly suitable for the remote transmission of information.     

图像融合质量客观评价方法

 随着图像融合技术的快速发展,科学的图像融合质量客观评价对选择合理的融合算法以及研究新的融合算法具有重要的指导意义,成为图像质量评价研究的热点。理想的图像质量客观评价方法可以给出与人主观感受相一致的量化指标。对目前已提出的多种图像融合质量客观评价算法进行综述。简要介绍了基本的客观评价指标;将基于边缘保持度、基于结构相似度、基于信息论以及基于对比度的4类客观评价算法分别进行了介绍,着重分析和比较了各类算法的思路及特点;总结融合图像质量客观评价算法的研究趋势,指出无参考图像与彩色融合图像的质量评价方法是未来重要的发展方向。     

Security analysis and improvement on a double-random phase-encoding technique based information hiding method

The security of an information hiding method using the double-random phase-encoding technique is analyzed and improved. The method encodes the hidden image with the double-random phase-encoding technique, and then embeds the real and imaginary parts of the encoded image to an enlarged host image. Recovering the hidden image from the composed image does not need the original host image, while the quality of the reconstructed image is satisfying. However, the original method is insecure in the sense of information hiding, since the composed image can be detected easily with some technical metrics. The security is improved by adding random perturbation on the encoded data. The validity of the improved method is demonstrated by numerical simulation experiments.     

Experimental opto-digital synthesis of encrypted sub-samples of an image to improve its decoded quality

We develop an experimental protocol to visualize decrypted images that otherwise would have been barely recognizable, while keeping the standard security levels. This image deterioration is partly due to the natural speckle noise as well as the practical limitations arising from the optical elements composing the setup. This protocol is based on an optical image synthesis with digital holography using enlarged sub-samples of an entire image together with a multiplexing technique. We implement the process using a Mach-Zehnder interferometer with a joint transform correlator encrypting architecture. As a result, we get smaller speckle patterns on the final assembled image and a spatial frequency enhancement with respect to the decoded image obtained with the conventional procedures.     

基于自适应平台阈值和拉普拉斯变换的红外图像增强

针对红外图像对比度低和边缘模糊的特点,提出了一种结合自适应平台直方图均衡化和拉普拉斯变换的方法。采用双数字信号处理器（DSP）并行处理,其中一片DSP采用自适应平台直方图均衡化的方法获得对比度增强后的图像;另一片DSP则进行拉普拉斯变换获得原始图像的边缘图像;最后由第二片DSP完成两幅图像按系数相乘后的叠加融合。实验结果表明：该算法增强效果和实时性较好,处理频率可达50 Hz,既提高了图像对比度又清晰了图像边缘,是提高图像对比度和边缘清晰度的高效算法。     

基于遥感图像及工程参数的全局像移探测算法

相邻两片成像传感器的拼接区能够形成具有相同目标景物的图像, 是提炼像移信息的关键, 具有相同目标景物的图像并非贯穿于每次成像任务全程, 无相同目标景物期间的像移估计问题仍然存在。提出基于遥感图像及工程参数的全局像移探测算法, 试图对包含无相同目标景物期间在内的像移进行全覆盖探测。根据拼接区成像特点, 将成像过程分为无相同目标景物和有相同目标景物两个阶段:在无相同目标景物阶段, 利用工程参数计算像移的低频分量, 建立基于拼接区图像和像移低频分量的目标函数, 衡量像移曲线与低频分量之间的偏离程度; 采用最速下降法搜索偏离度最小值点, 作为无相同目标景物期间像移的最优估计; 推导有相同目标景物期间的像移计算公式, 利用无相同目标景物期间的估计值求解像移。以XX-1号空间光学遥感器为实验对象, 检测到0.133 Hz、7 pixels左右的像移, 可探测的时间范围包含最初226 ms的无相同目标景物阶段, 且显著削弱了盲点处的像移测量偏差。实验结果证明, 提出的算法能够对包含无相同目标景物期间的全局像移进行有效测量。     

改进的曲波变换图像融合方法

考虑将曲波变换引入图像融合能够更好地提取原始图像,对一种新的图像融合方法—曲波变换图像融合法进行了研究。将图像序列进行曲波变换后,通过对所有图像的高频进行逆变换及域值处理来获得区域图。根据区域图中高频区域的边界点在每张图层上的活跃度不同求得区域边界的图层分布,利用插值获得高频区域的区域分布图。通过高频区域的膨胀求得整幅图的区域分布图,然后在曲波变换的变换域,利用区域分布图对多尺度的高频系数采用高斯加权求和;对低频系数采用取平均值的规则完成图像的融合。进行了图像融合实验,实验结果表明,与传统的小波变换及基于像素的曲波变换相比,提出的方法获得的融合图像边缘更清晰,更接近参考图像。     

An Investigation of the Temporal Dark-Image-Sticking Phenomenon in an AC Plasma Display Panel With an Auxiliary Electrode

In this paper, the temporal dark-image-sticking phenomenon in an ac plasma display panel (PDP) with an auxiliary electrode is investigated. To investigate this phenomenon, temporal behaviors of a black background image were observed in accordance with the sustain-discharge time and the relaxation time. Since dark image sticking is related to the reset discharge, our measurements focused on the reset period. In the case of an ac PDP with three electrodes, iterant sustain discharges induced an increase in black luminance, thereby leaving a residual image. However, in the case of an ac PDP with an auxiliary electrode, there was no variation of luminance between the states before and after the iterant sustain discharges. As a result, no residual image remained, and no distortion of the image could be recognized with the human eye, even after iterant sustain discharges.      

An improved image alignment procedure for high-resolution transmission electron microscopy

Image alignment is essential for image processing methods such as through-focus exit-wavefunction reconstruction and image averaging in high-resolution transmission electron microscopy. Relative image displacements exist in any experimentally recorded image series due to the specimen drifts and image shifts, hence image alignment for correcting the image displacements has to be done prior to any further image processing. The image displacement between two successive images is determined by the correlation function of the two relatively shifted images. Here it is shown that more accurate image alignment can be achieved by using an appropriate aperture to filter the high-frequency components of the images being aligned, especially for a crystalline specimen with little non-periodic information. For the image series of crystalline specimens with little amorphous, the radius of the filter aperture should be as small as possible, so long as it covers the innermost lattice reflections. Testing with an experimental through-focus series of Si[1 1 0] images, the accuracies of image alignment with different correlation functions are compared with respect to the error functions in through-focus exit-wavefunction reconstruction based on the maximum-likelihood method. Testing with image averaging over noisy experimental images from graphene and carbon-nanotube samples, clear and sharp crystal lattice fringes are recovered after applying optimal image alignment.     

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.     

大面积X射线分幅变像管的设计

提出了一种实现大工作面积分幅变像管的方法。设计了一种大输入光电阴极、小输出图像的静电聚焦变像管,输出端配接常规小工作面积快门选通微通道板（MCP）分幅管单元,实现图像选通和增强功能。这种分幅变像管与直接采用大面积MCP相比,不仅省去了制作大面积MCP的高昂成本,而且避免了由于微带线过长引起的选通脉冲传输衰减大、增益不均匀性严重等固有缺陷。设计的分幅变像管输入阴极有效直径100 mm,输出图像直径40 mm,放大倍率为0.4。中心空间分辨力达到14.4 lp/mm,边缘空间分辨力达到11.2 lp/mm,几何畸变不超过15%,其分幅特性由MCP分幅单元决定。     

基于曲率滤波和梯度变换的图像增强

针对基于梯度变换的图像增强算法抗噪声干扰能力差的问题,引入曲率滤波理论,提出了基于高斯曲率滤波和梯度变换的图像增强算法.该算法通过对图像梯度场进行非线性变换来增强图像对比度,通过构造能量泛函,采用梯度下降法从变换后的梯度场重构出增强后的图像,并利用高斯曲率滤波对梯度下降法迭代过程中的重构图像及其各阶偏微分进行平滑,有效解决了图像重构过程中的噪声非线性放大和扩散问题,同时保留了丰富的细节信息.采用多组边缘模糊图像进行仿真实验,实验结果表明该算法在增强图像边缘对比度的同时,能够有效抑制噪声.     

基于小波变换的磁共振图像去噪

去噪是图像处理中的一个非常重要的问题. 传统去噪方法在降低噪声的同时会模糊图像的细节,基于小波变换的图像去噪方法能在降低图像噪声的同时较好地保持图像的细节,目前基于小波变换对图像进行去噪已经成为最有前途的去噪方法之一. 本文综合小波域去噪的文献,对小波域的磁共振图像去噪方法进行了综述,详细介绍了各种小波域的磁共振图像去噪方法,并对他们的性能进行了总结,对小波域去噪方法的发展趋势进行了展望.     

Phase Imaging with a Phase-Shifting X-ray Shearing Interferometer Using an X-ray Line Source

An X-ray shearing interferometer with a line source is presented. The line source broadens X-ray beams and enables us to obtain a phase image with an X-ray image sensor without mechanical scanning. It can reduce the measuring time compared with image acquisition by mechanical scanning. Small phase difference is measured with the phase shift method using acrylic wedges. Although the output beam is overlapped with the non-interfering beams, we can obtain interference fringes with reasonable contrast. With this system we can obtain a projected phase image of an acrylic plate with cellophane tape.     

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.     

Hyperspectral image fusion based on sparse constraint NMF

The spatial resolution of hyperspectral image is often low due to the limitation of the imaging spectrometer. Fusing the original hyperspectral image with high-spatial-resolution panchromatic image is an effective approach to enhance the resolution of hyperspectral image. However, it is hard to preserve the spectral information at the same time of enhancing the resolution by the traditional fusion methods. In this paper, we proposed a fusion method based on the spectral unmixing model called sparse constraint nonnegative matrix factorization (SCNMF). This method has a superior balance of the spectral preservation and the spatial enhancement over some traditional fusion methods. In addition, the added sparse prior and NMF based unmixing model make the fusion more stable and physically reasonable. This method first decomposes the hyperspectral image into an endmember-matrix and an abundance-matrix, then sharpens the abundance-matrix with the panchromatic image, finally obtains the fused image by solving the spectral constraint optimization problem. The experiments on both synthetic and real data show the effectiveness of the proposed method.     

New enhancement of infrared image based on human visual system

Infrared images are firstly analyzed using the multifractal theory so that the singularity of each pixel can be extracted from the images. The multifractal spectrum is then estimated, which can reflect overall characteristic of an infrared image. Thus the edge and texture of an infrared image can be accurately extracted based on the singularity of each pixel and the multifractal spectrum. Finally the edge pixels are classified and enhanced in accordance with the sensitivity of human visual system to the edge profile of an infrared image. The experimental results obtained by this approach are compared with those obtained by other methods. It is found that the proposed approach can be used to highlight the edge area of an infrared image to make an infrared image more suitable for observation by human eyes.     

Incremental calculation for large deformation measurement using reliability-guided digital image correlation

Conventional digital image correlation (DIC) technique using a fixed reference image provides high-accuracy measurements but normally fails when serious decorrelation effect occurs in the deformed images due to large deformation, serious illumination fluctuations or other reasons. In this paper, an incremental reliability-guided digital image correlation (RG-DIC) technique, by combining the recently developed RG-DIC technique and an automatic reference image updating scheme, is proposed for large deformation measurement. In the incremental RG-DIC technique, a seed point is defined in the original reference image and searched in the deformed images, if the estimated correlation coefficient is larger than a preset threshold, which means no serious decorrelation effect exists in the deformed image, the RG-DIC technique is used to continue correlation analysis to obtain full-field displacements. Otherwise, the image recorded just before the current deformed image is chosen as an updated reference image to proceed with correlation analysis. Afterwards, the incremental displacements extracted by comparing the current deformed image and the updated reference image can be cumulated to determine the overall deformation. The effectiveness of the proposed technique is demonstrated by retrieving the full-field deformation of a foam sample subjected to large compressive deformation.     

A holographic image printing technique with high resolution

A method is shown to obtain a real image with a large image field and high resolution from an image hologram, which is produced by a large aperture lens with large amount of aberration. The resolution of the reconstructed serial image is estimated to be within the range from 450 to 500 lines/mm in 2 inch diameter image field.