A polynomial hybrid reflection model and measurement of its parameters based on images of sample

Reflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real reflectance. But the ratio of diffuse and specular reflection decided manually has no clear meaning.We propose a new polynomial hybrid reflectance model. The reflectance map equation with a known shape (for example cylinder) as a sample is used to estimate parameters of the proposed reflectance model by least square regression algorithm. Then the reflectance parameters for surfaces of the same class of materials can be determined. Experiments are performed for a metal surface. The synthesis images produced by the proposed method and existing ones are compared with the real acquired image, and the results show that the proposed reflectance model is suitable for describing real reflectance.     

基于IR-SFS算法空间目标红外影像3D重建

在利用单幅影像的明暗恢复形状（Shape From Shading,SFS）三维重构算法的基础上,提出同时考虑外界辐射源和目标自身红外辐射的IR-SFS（infrared-SFS）算法。首先通过分析SFS算法原理和空间目标的红外成像特性,建立IR-SFS辐射方程并进行了仿真研究,然后利用温度场估计获得红外差值图,在人工合成的理想半球体、半圆柱体卫星红外影像上进行算法测试,并以美国STS107真实红外影像作为实验目标进行三维重建。实验结果表明,所提出IR-SFS算法经过参数优化后,与原SFS算法相比,重建模型的峰值信噪比更高,对STS107顶部舱门、尾翼、机舱、机舱内方形部件具有更佳显示度,整体效果得到明显改善。     

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。     

基于视觉心理学的SFS流形算法研究

通过视觉方法获取形状在科学研究及工程实践中有着重要作用,灰度图像是最容易获取的视觉信息之一。目前由灰度重构的形状(SFS,shape from shading)受到了广泛的关注,但现有的算法稳定性差、效率低,一直阻碍着SFS方法的推广应用。受近期的视觉心理学研究成果的启发,针对SFS问题,从局部分析入手,即:在图像上,在每一灰度极值点附近,根据灰度单调变化的情况,形成一个椭圆形邻域,对应着表面凹凸区;在每一椭圆域上,形状可用抛物面逼近,其参数可由局部辐射度约束求解;整个图像被椭圆形邻域覆盖,这些覆盖可构成一个二维流形;借助于流形上单位分解函数,各局部抛物面粘合在一起,形成光滑的整体形状;总体形状在整幅图像的灰度约束下再进行全局优化,可得到最终的重构结果。给出了初步算例,算法的稳定性和效率均有大幅度提高。     

基于四叉树和偏微分方程的灰度图像压缩

提出了一种基于四叉树和偏微分方程的灰度图像压缩方法。该方法只需传输和处理部分稀疏像素而不是整幅灰度图像。在编码端,首先采用四叉树分割图像,然后对部分像素进行编码传输。在解码端,采用基于偏微分方程的图像插值算法再生图像,有效地消除了解码图像中的方块效应。实验表明,该方法可以获得较高的压缩比和峰值信噪比,尤其是对尺寸较大且纹理细节较少的图像更是如此,并能较好地保持原始图像中灰度变化较大的细节,可以方便地去除方块效应,具有较高的实用价值。     

基于图像融合的动态轮廓线跟踪新方法

红外与可见光传感器是目标跟踪识别系统中常用的两种传感器,对这两种传感器图像进行融合能有效提高系统跟踪检测的准确性。将动态轮廓线模型与图像融合结合,在特征搜索过程中利用特征点准确地完成了图像配准,同时使用了一种新的特征级融合方法,将两种图像中目标轮廓的B样条曲线控制点进行实时微分耦合。这种耦合将Curwen提出的微分耦合机制作了改进,利用图像配准把刚性硬模板改变为实时的变换模板并推导了融合后动态轮廓线的新的动力学方程。这种融合利用了红外图像目标轮廓信息约束可见光图像中动态轮廓线的收敛形状,有效地提高了可见光图像目标跟踪的准确性。对运动人手序列图像的对比跟踪实验表明,这种融合使得可见光图像中动态轮廓线平均跟踪误差减小了60．25％。     

Image encryption based on permutation-substitution using chaotic map and Latin Square Image Cipher

In this paper we presented a image encryption based on permutation-substitution using chaotic map and Latin square image cipher. The proposed method consists of permutation and substitution process. In permutation process, plain image is permuted according to chaotic sequence generated using chaotic map. In substitution process, based on secrete key of 256 bit generate a Latin Square Image Cipher (LSIC) and this LSIC is used as key image and perform XOR operation between permuted image and key image. The proposed method can applied to any plain image with unequal width and height as well and also resist statistical attack, differential attack. Experiments carried out for different images of different sizes. The proposed method possesses large key space to resist brute force attack.     

Analysis and synthesis of multicolored objects in a single image

We present a method with which to recover the intrinsic shading and reflectance characteristics of multicolored three-dimensional objects in a single image, with which realistic new scenes can be synthesized. A color watershed algorithm, which is based on a regularized dichromatic fitting error, is proposed for robust image segmentation. For shading recovery in small regions, a weighted interpolation is employed, whereas in large regions the reflectance and shading are calculated based on the assumption of gradual shape variation. It is demonstrated that the proposed method is promising and can be applied in image simulation.     

一种抗噪分形维计算方法及其在声纳图像识别中的应用

用于计算图像分形维的差分盒计数法(DBC)和鲁棒差分盒计数法(RDBC)都对脉冲噪声和斑点噪声较敏感,为此本文提出一种抗噪差分盒计数法(NRDBC),利用剪切局部标准差(TLSD)来计算图像分形维,由于TLSD可有效滤除脉冲噪声和斑点噪声、且对高斯噪声敏感性小,因此NRDBC能对有噪图像进行可靠的分形维估计。利用多分辨率的DBC、RDBC和NRDBC对混有高斯噪声、脉冲噪声和斑点噪声的7种Brodatz纹理以及3种海底的侧扫声纳图像进行了分类实验,结果表明,本文提出的NRDBC可获得更高的识别率和更好的抗噪性。     

光纤陀螺用掺铒超荧光光纤光源输出特性研究

介绍了掺铒超荧光光纤光源(SFS)的基本原理和SFS各种基本结构的特点。结合实际应用选择了单程后向(SPB) SFS作为光纤陀螺用光源。理论分析了影响单程后向掺铒超荧光光纤光源输出特性的各种因素。通过实验分析了铒纤长度对单程后向掺铒光纤光源泵浦效率和输出光谱的影响,特别是对中心波长稳定性的影响,对于单程后向结构掺铒光纤光源来说,铒纤长度有一个最佳值。演示了铒纤在选择最佳长度的情况下,泵浦功率对输出谱型的影响。通过实验分析了-40℃～60℃之间光源输出光谱和输出光功率的温度稳定性。最终得到了适用于惯导级光纤陀螺的光源。     

用于MR图像非局域均值去噪的边缘增强策略

非局域均值(NLM)滤波有很好的去噪效果并已成功地应用于磁共振图像的去噪中,但与所有去噪方法相同,总是会在一定程度上模糊图像细节. 该文提出将从原始图像中提取出来的高频信息与NLM去噪图像相融合,来还原在去噪过程中丢失的细节. 首先利用一种基于拉普拉斯金字塔的多分辨率方法,从原始图像中提取出包含丰富的边缘信息的高频组分. 然后利用作者提出的一种新的基于SUSAN算子的边缘检测算子产生一幅连续的边缘图,并利用该边缘图将高频组分与NLM方法去噪的图像相融合. 该方法在图像的平滑区域取得了良好的去噪效果,同时可以保留甚至增强图像的细节. 同时,该方法对图像的增强不会导致增强图像中常见的伪影.     

Infrared and visible image fusion method based on saliency detection in sparse domain

Infrared and visible image fusion is a key problem in the field of multi-sensor image fusion. To better preserve the significant information of the infrared and visible images in the final fused image, the saliency maps of the source images is introduced into the fusion procedure. Firstly, under the framework of the joint sparse representation (JSR) model, the global and local saliency maps of the source images are obtained based on sparse coefficients. Then, a saliency detection model is proposed, which combines the global and local saliency maps to generate an integrated saliency map. Finally, a weighted fusion algorithm based on the integrated saliency map is developed to achieve the fusion progress. The experimental results show that our method is superior to the state-of-the-art methods in terms of several universal quality evaluation indexes, as well as in the visual quality.     

基于冠层辐射传输模型的地表反射率光谱重建方法

针对基于多光谱数据有限光谱信息重建地表反射率光谱的病态求解难题,提出一种基于冠层辐射传输物理机理并充分考虑像元异质性的地表反射率光谱重建方法,该方法假设混合像元由植被和土壤两种地物类型组成,利用冠层辐射传输模型构造端元光谱查找表,进而通过组分比例因子估算实现基于多光谱图像的高光谱地表反射率模拟。以Landsat ETM+多光谱图像为例的地表反射率超光谱重建验证实验结果表明,模拟的反射率光谱能够较好的反映不同地物特征信息。进一步地,利用模拟的地表反射率拟合Landsat ETM+图像和MODIS图像,各波段模拟图像与实际观测图像之间具有较高的相关系数(Landsat: 0.90~0.99, MODIS: 0.74~0.85),进一步验证了该方法的可行性。     

Fringe contrast-based 3D profilometry using fringe projection

Quality-guided algorithm is a widely used method in phase unwrapping. This paper shows an accurate quality map based on fringe contrast for 3D shape measurement. Phase-shifted fringe patterns are projected onto an object surface by a programmable liquid crystal projector and recorded by a CCD camera. A wrapped phase map and a fringe contrast map are extracted from the deformed fringe patterns by the phase-shifting technique. Guided by the contrast map, the quality-guided unwrapping algorithm minimizes unwanted shadow and non-uniform surface reflectance effects and is able to retrieve a correct surface profile. Validity of the proposed method is tested on a fish model and a cutting tool specimen.     

基于光子图海水点扩展函数的估计

海水中粒子对光的散射是水下图像模糊的主要原因。点扩展函数能够反映海水中光的空间扩散程度,使用点扩展函数,水下图像能被恢复或增强。提出了一种基于光子图海水点扩展函数的估计方法,该方法通过用光子图求解辐射传输方程,对光场内任意点的辐射强度进行估计。通过与蒙特卡洛仿真点扩展函数的方法相比较,结果表明两者具有较好的一致性。     

A robust and secure chaotic standard map based pseudorandom permutation-substitution scheme for image encryption

A novel and robust chaos-based pseudorandom permutation-substitution scheme for image encryption is proposed. It is a loss-less symmetric block cipher and specifically designed for the color images but may also be used for the gray scale images. A secret key of 161-bit, comprising of the initial conditions and system parameter of the chaotic map (the standard map), number of iterations and number of rounds, is used in the algorithm. The whole encryption process is the sequential execution of a preliminary permutation and a fix number of rounds (as specified in the secret key) of substitution and main permutation of the 2D matrix obtained from the 3D image matrix. To increase the speed of encryption all three processes: preliminary permutation, substitution and main permutation are done row-by-row and column-by-column instead of pixel-by-pixel. All the permutation processes are made dependent on the input image matrix and controlled through the pseudo random number sequences (PRNS) generated from the discretization of chaotic standard map which result in both key sensitivity and plaintext sensitivity. However each substitution process is initiated with the initial vectors (different for rows and columns) generated using the secret key and chaotic standard map and then the properties of rows and column pixels of input matrix are mixed with the PRNS generated from the standard map. The security and performance analysis of the proposed image encryption has been performed using the histograms, correlation coefficients, information entropy, key sensitivity analysis, differential analysis, key space analysis, encryption/decryption rate analysis etc. Results suggest that the proposed image encryption technique is robust and secure and can be used for the secure image and video communication applications.     

基于约束共轭梯度的高能闪光照相图像复原算法

 针对闪光照相系统模糊较大、成像信噪比低的特点,提出了一种基于约束共轭梯度的闪光照相图像复原算法,将闪光照相图像复原问题转化为一个约束优化问题,引入基于非负、中值滤波和偏微分方程的光滑约束条件,并利用约束共轭梯度法迭代求最优解。数值试验表明,该算法能较好再现图像边缘信息,复原出的图像在信噪比和视觉方面都有较大提高。     

高稳定宽频带掺铒光纤超荧光光源

理论研究了双程后向结构掺铒光纤超荧光光源的特性。结果表明 ,在任意反射镜参数下 ,只要选取适当的掺铒光纤长度 ,该结构光源总能实现不依赖于抽运功率的平均波长高稳定性运行 ;在光源高稳定性的前提下 ,反射镜参数优化后的该结构光源具有较宽的频带宽度和较高的抽运效率     

基于小波概率估计的图像融合方法研究

在研究了已有的图像融合方法后,提出基于小波变换和最大似然概率估计(MLE)相综合的融合方法,利用概率估计融合模型,首先对不同的传感器图像进行小波分解,然后对相应的子带求解仿射变换参数,根据Bayes规则进行最大后验概率似然估计,得到估计子带系数,最后通过小波反变换得到融合图像.在仿射变换的假设条件下定义融合规则,更适合传感器图像具有局部相反对比度的情况,采用此方法对航空可见光图像和红外图像进行融合实验,其结果与采用其它方法进行了对比,表明该方法的有效性.     

基于非线性偏微分方程的灰度图像骨架线提取方法

基于变分法提出用于计算灰度图像梯度矢量场的非线性偏微分控制方程,利用图像梯度矢量场的拓扑性,可实现骨架线的提取。该方法的主要优点是它的简单性,可直接应用于灰度图像,不需要任何的分割处理。把提出的方法应用于牛顿环干涉条纹中,并与广泛使用的分块二值化细化算法和极值跟踪法进行了比较,实验结果表明了本方法的良好性能。