基于能谱CT的材料组分彩色表征研究

基于光子计数探测器的X射线能谱CT,通过增加能谱分辨率实现了CT图像由灰度向彩色的转变,提高了材料识别能力。然而随着能谱通道数量的增加,通道中的噪声也显著增加,降低了材料识别的准确性。为充分利用能谱CT图像的稀疏性以及能谱通道之间图像的相关性,提出一种多约束窄谱CT迭代重建算法,可在降低噪声的同时有效保留图像的边缘及细节部分。进一步利用主成分分析对窄谱CT图像中的能谱信息进行估计,并建立主成分图像与R,G和B颜色分量之间的映射关系,最后获取彩色CT图像。该方法通过材料组分的彩色表征可以有效识别材料,同时降低图像中的背景噪声。仿真实验和实际实验结果验证了多约束窄谱CT迭代重建算法的有效性以及利用主成分分析进行材料组分彩色表征的可行性。     

Computer-generated kinoforms of real-existing full-color 3D objects using pure-phase look-up-table method

A computational method based on pure-phase look-up-table (LUT) is proposed for generating kinoforms of full-color real-existing three-dimensional (3D) objects. The principle of the pure-phase LUT method is described. 3D depth as well as color information of a full-color 3D object is obtained by the full-color 3D profile measurement approach based on binocular vision. The obtained full-color 3D data is decomposed into red (R), green (G), and blue (B) channels, and kinoforms of each channel are calculated from the depth map and color information of the corresponding channel using the pure-phase LUT method. In order to reduce the speckle noise of reconstructed full-color 3D image, sequential kinoforms of each color channel are generated by adding dynamic-pseudorandom phase factor into the object domain. Numerical reconstruction and optical reconstruction with a phase-only spatial light modulator (SLM) show that, with the proposed method, full-color holographic 3D display of real-existing full-color 3D objects is available.     

Optical color image encryption based on the wavelength multiplexing using cascaded phase-only masks in Fresnel transform domain

A novel technique, based on a modified Gerchberg–Saxton algorithm (MGSA) in the Fresnel-transform (FrT) domain, is proposed to encode a color image into three phase-only functions (POFs) for three separated channels: red (R), green (G), and blue (B). The decomposed three RBG channels can avoid the interference of crosstalks efficiently. In proposed decryption process, a color image can be promptly reconstructed by summing of the three decrypted RGB images after the created three POFs which are decrypted one by one. In this paper, all the created three POFs and the system parameters of FrT can be used as the keys for increasing security that are also demonstrated. The computer application simulations to the partial color encryption and decryption are given to validate the feasibility of the proposed scheme.     

基于相位相关的匀速直线运动模糊图像位移参数估计

为估算匀速直线运动模糊图像的运动参数,提出了一种基于相位相关分析的图像配准方法。该方法利用傅里叶变换的平移特性,对产生平移的目标图像进行傅里叶变换并计算归一化互功率谱,其傅里叶逆变换对应二维脉冲函数,通过计算脉冲函数峰值坐标获取位移图像之间的亚像元级位移量。结合相位相关配准原理和线性空间不变退化模型,给出了匀速直线运动点扩散函数及其光学传递函数的数学描述;讨论了匀速直线运动模糊对相位相关配准结果的影响,证明了图像经过匀速直线运动退化后,位移图像之间归一化互功率谱具有不变性。实验结果表明：动态运动模糊图像最大检测误差为0.489 pixel,标准差为0.16 pixel。     

A novel color image encryption algorithm based on genetic recombination and the four-dimensional memristive hyperchaotic system

Recently, many image encryption algorithms based on chaos have been proposed. Most of the previous algorithms encrypt components R, G, and B of color images independently and neglect the high correlation between them. In the paper, a novel color image encryption algorithm is introduced. The 24 bit planes of components R, G, and B of the color plain image are obtained and recombined into 4 compound bit planes, and this can make the three components affect each other. A four-dimensional(4D) memristive hyperchaotic system generates the pseudorandom key streams and its initial values come from the SHA 256 hash value of the color plain image. The compound bit planes and key streams are confused according to the principles of genetic recombination, then confusion and diffusion as a union are applied to the bit planes,and the color cipher image is obtained. Experimental results and security analyses demonstrate that the proposed algorithm is secure and effective so that it may be adopted for secure communication.     

Single-channel color image encryption using phase retrieve algorithm in fractional Fourier domain

A single-channel color image encryption is proposed based on a phase retrieve algorithm and a two-coupled logistic map. Firstly, a gray scale image is constituted with three channels of the color image, and then permuted by a sequence of chaotic pairs generated by the two-coupled logistic map. Secondly, the permutation image is decomposed into three new components, where each component is encoded into a phase-only function in the fractional Fourier domain with a phase retrieve algorithm that is proposed based on the iterative fractional Fourier transform. Finally, an interim image is formed by the combination of these phase-only functions and encrypted into the final gray scale ciphertext with stationary white noise distribution by using chaotic diffusion, which has camouflage property to some extent. In the process of encryption and decryption, chaotic permutation and diffusion makes the resultant image nonlinear and disorder both in spatial domain and frequency domain, and the proposed phase iterative algorithm has faster convergent speed. Additionally, the encryption scheme enlarges the key space of the cryptosystem. Simulation results and security analysis verify the feasibility and effectiveness of this method.     

基于光饱和影响校正的作物叶绿素分布光谱成像检测

叶绿素含量是作物光合能力与营养评价的重要指标,因此快速检测作物叶绿素含量与分布可为作物营养动态分析与长势评估提供支持。基于RGB(Red, Green, Blue)和NIR(Near Infrared)多光谱图像的获取,开展玉米作物营养状态分布光谱学成像检测。构建了多光谱图像采集平台获取RGB和NIR图像,研究了基于光饱和校正算法的RGB图像的光饱和校正与NIR图像去噪方法,通过图像的匹配分割,冠层的提取校正,建立了基于冠层图像的作物SPAD值检测模型与分布成图。采集15株玉米植株RGB-NIR图像,并同步获取不同植株,不同位置共68个叶绿素含量指标SPAD值。首先对RGB图像进行光饱和校正,再对NIR图像进行滤波和图像增强,其次对RGB和NIR图像进行了SURF(speeded-up robust features)和RANSAC(random sample consensus)图像匹配,利用RGB图像的颜色特征,采用ExG(Extra Green)和OTSU算法生成分割掩模,对RGB图像和NIR图像进行分割提取,提取图像的R, G, B和NIR分量,利用4阶灰度板进行反射率校正,然后计算作物图像中像素级P_SPAD值,并建立图像P_SPAD值与叶绿素仪SPAD值的拟合模型,最后绘制作物SPAD分布图。通过HSI(Hue, Saturation, Intensity)彩色模型中的I分量直方图对比去饱和前后光分布范围,以作物SPAD值分布图验证光饱和校正算法对作物叶绿素含量分布检测提升的效果。RGB图像光饱和校正前I分量集中在[140～180]之间,光饱和校正后的RGB图像I分量集中在[85～130]之间, 校正了相机成像时产生模糊和RGB图像饱和。对分割后的RGB图像和NIR图像提取R,G,B,NIR分量进行4阶灰度板校正,相关系数分别为0.829,0.828,0.745和0.994,进而生成R,G,B和NIR四波段的反射率伪彩色图像,反射率R_NIR＞R_C＞R_R＞R_B。体现了作物的在蓝光和红光区域吸收光,在绿光区域和近红外区域反射光的光谱特性。校正前后的R和NIR分量反射率计算图像P_SPAD值拟合叶绿素含量指标SPAD值的模型结果显示,校正前R2为0.332 6,校正后R2为0.619 3,绘制作物的SPAD特征分布图,可为作物的营养动态快速分析与分布检测提供技术支持。     

Optical color image encryption based on Arnold transform and interference method

In this paper, we propose a novel method to encrypt a color image based on Arnold transform (ART) and interference method. A color image is decomposed into three independent channels, i.e., red, green and blue, and each channel is then encrypted into two random phase masks based on the ART and interference method. Light sources with corresponding wavelengths are used to illuminate the retrieved phase-only masks during image decryption. The influence of security parameters on decrypted images is also analyzed. Numerical simulation results are presented to illustrate the feasibility and effectiveness of the proposed method.     

Multiple color-image fusion and watermarking based on optical interference and wavelet transform

A novel multiple color-image fusion and watermarking using optical interference and wavelet transform is proposed. In this method, each secret color image is encoded into three phase-only masks (POMs). One POM is constructed as user identity key and the other two POMs are generated as user identity key modulated by corresponding secret color image in gyrator transform domain without using any time-consuming iterative computations or post-processing of the POMs to remove inherent silhouette problem. The R, G, and B channels of different user identity keys POM are then individually multiplied to get three multiplex POMs, which are exploited as encrypted images. Similarly the R, G, and B channels of other two POMs are independently multiplied to obtain two sets of three multiplex POMs. The encrypted images are fused with gray-level cover image to produce the final encrypted image as watermarked image. The secret color images are shielded by encrypted images (which have no information about secret images) as well as cover image (which reveals no information about encrypted images). These two remarkable features of the proposed system drastically reduce the probability of the encrypted images to be searched and attacked. Each individual user has an identity key and two phase-only keys as three decryption keys besides transformation angles regarded as additional keys. Theoretical analysis and numerical simulation results validate the feasibility of the proposed method.     

Switching non-local vector median filter

This paper describes a novel image filtering method that removes random-valued impulse noise superimposed on a natural color image. In impulse noise removal, it is essential to employ a switching-type filtering method, as used in the well-known switching median filter, to preserve the detail of an original image with good quality. In color image filtering, it is generally preferable to deal with the red (R), green (G), and blue (B) components of each pixel of a color image as elements of a vectorized signal, as in the well-known vector median filter, rather than as component-wise signals to prevent a color shift after filtering. By taking these fundamentals into consideration, we propose a switching-type vector median filter with non-local processing that mainly consists of a noise detector and a noise removal filter. Concretely, we propose a noise detector that proactively detects noise-corrupted pixels by focusing attention on the isolation tendencies of pixels of interest not in an input image but in difference images between RGB components. Furthermore, as the noise removal filter, we propose an extended version of the non-local median filter, we proposed previously for grayscale image processing, named the non-local vector median filter, which is designed for color image processing. The proposed method realizes a superior balance between the preservation of detail and impulse noise removal by proactive noise detection and non-local switching vector median filtering, respectively. The effectiveness and validity of the proposed method are verified in a series of experiments using natural color images.     

A novel color image encryption scheme using alternate chaotic mapping structure

This paper proposes an color image encryption algorithm using alternate chaotic mapping structure. Initially, we use the R, G and B components to form a matrix. Then one-dimension logistic and two-dimension logistic mapping is used to generate a chaotic matrix, then iterate two chaotic mappings alternately to permute the matrix. For every iteration, XOR operation is adopted to encrypt plain-image matrix, then make further transformation to diffuse the matrix. At last, the encrypted color image is obtained from the confused matrix. Theoretical analysis and experimental results has proved the cryptosystem is secure and practical, and it is suitable for encrypting color images.     

基于亚像素区域加权能量特征的多尺度图像融合算法

对矩形和圆形区域中各像素进行亚像素划分,确定各亚像素的权值,得到基于哑像素的综合加权区域能量.融合箅法首先对源图像进行金字塔分解,然后对金字塔的高频细节分量使用基于哑像素加权区域能量特征的融合规则取大,对低频粗糙分量取平均.得到融合图像的塔形分解,最后重构融合图像.仿真结果表明,新算法融合效果较常规的区域能量特征作为融合规则的多分辨率图像融合算法效果更好,从清晰度和熵的评价来看,提高了融合图像的品质.     

彩色图像的非相干光相关识别

提出一种用非相干光系统识别彩色图像的方法,将脸色图像分解成三个单色像处理,设计一可实现的仅相位光学传递函数,对其进行带能优化,人而提高信噪比并使相关峰锐化,通过一对滤波器来合成该光学传递函数,获得了采色图像相关识别的实验结果。     

Color image encryption based on interference and virtual optics

We propose two approaches to encrypt color images based on interference and virtual optics. In the first method, a color image is first decomposed into three independent channels, i.e., red, green and blue. Each channel of the input image is encrypted into two random phase-only masks based on interference. In the second method, a color image is first converted into an image matrix and a color map, and only the image matrix is encrypted into random-phase masks based on interference. After the phase masks are retrieved, a concept based on virtual optics is further applied to enhance the security level. Numerical simulations are demonstrated to show the feasibility and effectiveness of the proposed methods.     

Enhanced Optical Image Verification Based on Joint Transform Correlator Adopting Fourier Hologram

In this paper two new architectures for optical image verification are proposed. Both architectures are based on conventional joint transform correlators (JTCs) adopting a Fourier hologram and can significantly improve the recovered image quality. First, an input phase-only function is Fourier transformed and then interferes with a reference wave that is diffracted from a plane wave incident on another random phase mask. Second, two phase-only functions are placed at the two input sides of a beamsplitter such that the interference pattern of their Fourier transforms can be detected. To obtain a predefined target image in the output plane, one of the input phase functions is iteratively retrieved by the use of the projection onto constraint sets algorithm. Simulation results show that the less mean squared error and better image quality are obtained for both the binary and grayscale images.     

A novel color fringe projection based Fourier transform 3D shape measurement method

A novel Fourier transform 3D shape measurement method based on color fringe projection is proposed in order to solve the spectrum overlapping and phase unwrapping problems existed in Fourier transform profilometry (FTP). The R and G components of the color fringe are set to two sinusoidal patterns with different frequencies and the B component is set to the average value of R or G component. Then this pattern is projected to the object and the deformed fringe image is captured. Three gray patterns are separated from the color fringe, the background and high frequency noise can be eliminated using our method and the accurate unwrapped phase can be got. Only one shot color pattern is projected to get the 3D information of the object. Experiment results show that the 3D information of an object can be obtained rapidly and accurately.     

An Optimized Quantum Representation for Color Digital Images

With the continuous development of quantum computation, quantum mechanics has been widely exploited to meet the storage requirement of high definition image. In this paper, an optimized quantum representation for color digital images (OCQR) is proposed, which makes full use of quantum superposition characteristic to store the RGB value of every pixel. Compared with latest novel quantum representation of color digital images (NCQI), OCQR uses nearly one-third times the qubits to store the pixel value. Meanwhile, some image processing operations related to color information can be executed more simultaneously and conveniently based on OCQR. Therefore, the proposed OCQR model is better suited to represent the quantum color image.     

RGB三通道衍射望远镜光学成像系统设计

基于目前研究较热的大口径衍射望远镜技术，提出一种在可见光范围内进行成像的衍射望远镜光学系统方案。该方案解决了目前衍射望远镜存在的成像频谱范围较窄的问题，可以在可见光范围内获取彩色图像，设计方法是将衍射元件沿径向分为3个通道，分别对R、G、B三个颜色通道进行成像，每个通道的成像带宽为40 nm，通过控制系统参数使3个通道的像在像面处重合，获取彩色图像。设计了基于25 m口径衍射主镜的三通道望远镜光学系统，并对该系统进行建模仿真，仿真结果与设计理论相符。该方案可以增加成像的频谱范围，其像面光斑具有与单通道系统像面光斑近乎相同的主瓣宽度。     

Optical color image hiding scheme by using Gerchberg–Saxton algorithm in fractional Fourier domain

We proposed an optical color image hiding algorithm based on Gerchberg–Saxton retrieval algorithm in fractional Fourier domain. The RGB components of the color image are converted into a scrambled image by using 3D Arnold transform before the hiding operation simultaneously and these changed images are regarded as the amplitude of fractional Fourier spectrum. Subsequently the unknown phase functions in fractional Fourier domain are calculated by the retrieval algorithm, in which the host RBG components are the part of amplitude of the input functions. The 3D Arnold transform is performed with different parameters to enhance the security of the hiding and extracting algorithm. Some numerical simulations are made to test the validity and capability of the proposed color hiding encryption algorithm.     

误差分散类彩色半调图的边缘检测算法

针对误差分散类彩色半调图提出一种边缘检测算法.首先应用K－L变换,将(R,G,B)空间转换为具有正交特性的彩色特征空间(I1,I2,I3),构造灰度图I使之包含所有单色图像的边缘信息,最后设计多尺度边缘检测模板以获取图像边缘.实验表明,算法较传统方法抗半调噪音的能力强,能快速、准确地提取彩色半调图像的边缘.