Shape-based interpolation of multidimensional grey-level images

Shape-based interpolation as applied to binary images causes the interpolation process to be influenced by the shape of the object. It accomplishes this by first applying a distance transform to the data. This results in the creation of a grey-level data set in which the value at each point represents the minimum distance from that point to the surface of the object. (By convention, points inside the object are assigned positive values; points outside are assigned negative values.) This distance transformed data set is then interpolated using linear or higher-order interpolation and is then thresholded at a distance value of zero to produce the interpolated binary data set. Here, the authors describe a new method that extends shape-based interpolation to grey-level input data sets. This generalization consists of first lifting the n-dimensional (n-D) image data to represent it as a surface, or equivalently as a binary image, in an (n+1)-dimensional [(n+1)-D] space. The binary shape-based method is then applied to this image to create an (n+1)-D binary interpolated image. Finally, this image is collapsed (inverse of lifting) to create the n-D interpolated grey-level data set. The authors have conducted several evaluation studies involving patient computed tomography (CT) and magnetic resonance (MR) data as well as mathematical phantoms. They all indicate that the new method produces more accurate results than commonly used grey-level linear interpolation methods, although at the cost of increased computation.     

Shape-based interpolation of multidimensional objects

A shape-based interpolation scheme for multidimensional images is presented. This scheme consists of first segmenting the given image data into a binary image, converting the binary image back into a gray image wherein the gray value of a point represents its shortest distance (positive value for points of the object and negative for those outside) from the cross-sectional boundary, and then interpolating the gray image. The set of all points with nonnegative values associated with them in the interpolated image constitutes the interpolated object. The method not only minimizes user involvement in interactive segmentation, but also leads to more accurate representation and depiction of dynamic as well as static objects. The general methodology and the implementation details of the method are presented and compared on a qualitative and quantitative basis to the existing methods. The generality of the proposed scheme is illustrated with a number of medical imaging examples.     

Morphology-based three-dimensional interpolation

In many medical applications, the number of available two-dimensional (2-D) images is always insufficient. Therefore, the three-dimensional (3-D) reconstruction must be accomplished by appropriate interpolation methods to fill gaps between available image slices. In this paper, we propose a morphology-based algorithm to interpolate the missing data. The proposed algorithm consists of several steps. First, the object or hole contours are extracted using conventional image-processing techniques. Second, the object or hole matching issue is evaluated. Prior to interpolation, the centroids of the objects are aligned. Next, we employ a dilation operator to transform digital images into distance maps and we correct the distance maps if required. Finally, we utilize an erosion operator to accomplish the interpolation. Furthermore, if multiple objects or holes are interpolated, we blend them together to complete the algorithm. We experimentally evaluate the proposed method against various synthesized cases reported in the literature. Experimental results show that the proposed method is able to handle general object interpolation effectively.     

Fast DCT-based spatial domain interpolation of blocks in images

An efficient method is presented to restore a block in an image, using a reduced set of border pixels. The basic assumption is that, if the set of pixels consisting of the missing block and its border pixels is transformed by the DCT, the high frequency coefficients obtained can be set to zero. A system of linear equations results, whose solution yields approximations for the values of the lost pixels. In this interpolation scheme, only eight border pixels are used in the computation of any missing pixel. Simulation results show that the approach generally outperforms alternative methods at a smaller computational cost.     

FPGA-based servo control and three-dimensional dynamic interpolation

The design and implementation of a field-programmable gate array (FPGA)-based controller that employs three-dimensional dynamic interpolation (3D/sup 2/I) for process and system dynamics compensation is described. A strategy for multiple-constraint based tool deflection compensation employing the 3D/sup 2/I mechanism is also presented as an example of the utility of the approach.     

A task-specific evaluation of three-dimensional image interpolation techniques

Image interpolation is an important operation that is widely used in medical imaging, image processing, and computer graphics. A variety of interpolation methods are available in the literature. However, their systematic evaluation is lacking. In a previous paper, we presented a framework for the task-independent comparison of interpolation methods based on certain image-derived figures of merit using a variety of medical image data pertaining to different parts of the human body taken from different modalities. In this work, we present an objective task-specific framework for evaluating interpolation techniques. The task considered is how the interpolation methods influence the accuracy of quantification of the total volume of lesions in the brain of multiple sclerosis (MS) patients. Sixty lesion-detection experiments coming from ten patient studies, two subsampling techniques and the original data, and three interpolation methods are carried out, along with a statistical analysis of the results.     

基于形状的图像检索技术研究

基于形状的图像检索技术是基于内容的图像检索技术的一个重要组成部分。现有的形状特征检索技术主要集中在形状特征的提取及相似性度量、形状特征与颜色和纹理特征结合、形状特征与高层的语义特征结合的研究。在分析现有的基于形状的图像检索技术的一些关键技术的基础上,对基于小波-傅里叶特征(WFD)的形状检索方法进行了研究,并提出了一些改进算法。结合Matlab和ACCESS实现了一个基于形状的图像检索实验系统,建立了用户界面,选取与设计了4个图像测试集,使用检索性能评价方法对形状特征的检索结果进行了客观的评价。实验结果表明,利用本文所提出改进的形状特征进行检索取得了较好的检索效果。     

Digital magnification of three-dimensional integral images

The methods for obtaining a controlled magnification of three-dimensional (3-D) integral images are usually based on the increase of the spatial ray-sampling rate of elemental image arrays. This is usually done by use of the moving array-lenslet technique. The major drawback of this technique is the alignment complexity due to the small lenslet movement. In this paper, we are proposing a digital magnification method that uses interpolation principles to increase the spatial ray sampling rate of elemental image arrays without lenslet movement in the pickup procedure. We compare the reconstructed 3-D integral images obtained when using the optical or the digital magnification methods, and show that the quality of both reconstructed 3-D integral images is the same.     

The display of three-dimensional video images

Three-dimensional images can be pixellated in three distinct ways: volumetric, holographic, and autostereoscopic. The latter excels if images of opaque objects are to be displayed with wide fields of view, and the quality of view-sequential displays with 1° per view now appears adequate for general applications. Although in principle autostereoscopic pixellation gives a true three-dimensional image, 1/10° per view is needed to avoid flaws in a typical display. This approximately equals the diffraction limit, and the information content is no less than that of a hologram. A hybrid of holographic views and view-sequential multiplexing promises images with the field of view of autostereoscopic images but the significantly greater resolution and depth of holograms. Light valves and high-frame-rate arrays already have the space-bandwidth product needed to display such images, and further advances in photonic switches and gigahertz telecommunications look set to promote the display of such high-quality three-dimensional video images     

Saturation-based adaptive inverse gradient interpolation for Bayerpattern images

A saturation-based adaptive gradient interpolation algorithm is developed for Bayer pattern images obtained in single-sensor digital cameras. The proposed algorithm uses the concept of pseudo-saturation for 2×2 blocks of the image. The algorithm adapts the scheme of interpolation based on the classification of the pseudo-saturation of Bayer pattern images. Compared with other algorithms, the proposed method preserves fine details, reduces false colours, and distortions around edges and sharp features of the colour image reconstructed from different kinds of Bayer pattern images     

Three-dimensional segmentation and interpolation of magnetic resonance brain images

The authors propose a method for the 3-D reconstruction of the brain from anisotropic magnetic resonance imaging (MRI) brain data. The method essentially consists in two original algorithms both for segmentation and for interpolation of the MRI data. The segmentation process is performed in three steps. A gray level thresholding of the white and gray matter tissue is performed on the brain MR raw data. A global white matter segmentation is automatically performed with a global 3-D connectivity algorithm which takes into account the anisotropy of the MRI voxel. The gray matter is segmented with a local 3-D connectivity algorithm. Mathematical morphology tools are used to interpolate slices. The whole process gives an isotropic binary representation of both gray and white matter which are available for 3-D surface rendering. The power and practicality of this method have been tested on four brain datasets. The segmentation algorithm favorably compares to a manual one. The interpolation algorithm was compared to the shaped-based method both quantitatively and qualitatively.     

Subpixel edge localization and the interpolation of still images

In this paper, we present a nonlinear interpolation scheme for still image resolution enhancement. The algorithm is based on a source model emphasizing the visual integrity of detected edges and incorporates a novel edge fitting operator that has been developed for this application. A small neighborhood about each pixel in the low-resolution image is first mapped to a best-fit continuous space step edge. The bilevel approximation serves as a local template on which the higher resolution sampling grid can then be superimposed (where disputed values in regions of local window overlap are averaged to smooth errors). The result is an image of increased resolution with noticeably sharper edges and, in all tried cases, lower mean-squared reconstruction error than that produced by linear techniques.     

CFA图像插值算法在DSP实时系统上的应用

彩色滤波阵列(CFA)格式的图像需要进行图像插值,才能获得全彩色图像.但是,由于相机噪声的存在,不仅该点的彩色信息失真,同时还会影响邻近像素利用该点信息进行插值的图像颜色.为了得到高质量的全彩色图像,采用了一种基于梯度的滤噪插值算法,在保留了图像边缘和细节信息的同时,滤除了噪声,使图像的信噪比提高了近1倍;由于这种数字相机没有白平衡处理,使插值恢复的彩色图像颜色与实际景物相比存在较大差异,为了消除这种差异,实现了自适应白平衡校正方法,使图像方差提高了近20％,与人眼观察到实际景物的颜色更接近;整个彩色编码算法应用了DSP的并行流水线技术,保证了其在DSP上运行的实时性,处理频率达到25Hz.     

Compression of multispectral images by three-dimensional SPIHTalgorithm

The authors carry out low bit-rate compression of multispectral images by means of the Said and Pearlman's SPIHT algorithm, suitably modified to take into account the interband dependencies. Two techniques are proposed: in the first, a three-dimensional (3D) transform is taken (wavelet in the spatial domain, Karhunen-Loeve in the spectral domain) and a simple 3D SPIHT is used; in the second, after taking a spatial wavelet transform, spectral vectors of pixels are vector quantized and a gain-driven SPIHT is used. Numerous experiments on two sample multispectral images show very good performance for both algorithms     

Rigorous analysis of three-dimensional structures incorporatingdielectrics

The paper presents the SR3D software (3D radiating structures), which calculates the electromagnetic characteristics of arbitrarily shaped structures incorporating dielectric material. The rigorous analysis method is based on the integral equation formulation. The authors included a variational approach using the reaction concept of Rumsey. The problem is numerically solved with a surface finite elements method. A guided mode excitation has been introduced in order to compute the reflection coefficient at the transmit port and the transmission coefficient between the different parts fed by guided modes. This software is validated by excellent agreement between simulated and measured radioelectric performances (patterns and SWR)     

Full-wave analysis of three-dimensional planar structures

An efficient numerical-analytical approach to the analysis of planar and waveguide three-dimensional structures is presented. To maintain high accuracy and fast convergence of solutions, the technique has been based on Galerkin's method in the spectral domain. The following has been achieved: (1) formulation of a diagonalized set of integral equations for problems associated with planar structures on multilayered uniaxial dielectric substrates; (2) development and application of complete orthonormalized sets of basis functions accounting the edge conditions in explicit form; and (3) development of efficient numerical quadratures for evaluating infinite singular integrals and improvement of the convergence of the integrals and series in the matrix elements of the algebraic system     

Decomposition of three-dimensional medical images into visual patterns

In this paper, we present a method for the decomposition of a volumetric image into its most relevant visual patterns, which we define as features associated to local energy maxima of the image. The method involves the clustering of a set of predefined bandpass energy filters according to their ability to segregate the different features in the image, thus generating a set of composite-feature detectors tuned to the specific visual patterns present in the data. Clustering is based on a measure of statistical dependence between pairs of frequency features. We will illustrate the applicability of the method to the initialization of a three-dimensional geodesic active model.     

Hierarchical ownership and deterministic watermarking of digital images via polynomial interpolation

This paper presents a novel method for the secure management of digital images formulated within the mathematical theory of polynomial interpolation. As main innovative features, our approach is based on a hierarchical joint ownership of the image by a trusted layered authority and on a deterministic watermarking procedure, embedding a short meaningful or random signature into the image. Experimental results show that the inserted signature can almost always be fully recovered even in presence of a reasonable amount of image degradation due to image processing operators, such as filtering, geometric distortions and compression.     

基于色差空间的Bayer 图像的迭代插值算法

单CCD/CMOS 传感器相机捕捉图像信息靠在传感器表面覆盖一层颜色滤波阵列(CFA),经过CFA 后每个像素点只能获得物理三基色(红,绿,蓝)其中一种分量。另外缺少的两种颜色分量,需要通过周围像素的值来估算。首先利用55 模板内的像素来估计插值的方向并用最优的权重系数来插值G 分量。其次利用了基于有理函数的二维插值算子在色差空间插值R(B)处缺少的B(R)分量。再次利用色差插值G 处缺少的R 和B 分量。最后,使用方差约束条件,迭代插值过程被重复多次直到达到了最优的插值结果。通过在24 幅柯达图片以及笔者相机拍摄的图片上的Matlab 仿真实验,结果显示,被提出的算法无论是在视觉方面还是在量化的数据方面都表现出了优势。