An axiomatic approach to image interpolation

We discuss possible algorithms for interpolating data given in a set of curves and/or points in the plane. We propose a set of basic assumptions to be satisfied by the interpolation algorithms which lead to a set of models in terms of possibly degenerate elliptic partial differential equations. The absolute minimal Lipschitz extension model (AMLE) is singled out and studied in more detail. We show experiments suggesting a possible application, the restoration of images with poor dynamic range.     

An improved image interpolation algorithm

The paper sets forth an improved edge-directed image interpolation algorithm with low time complexity which is the combination of Newton’s method and edge-directed method. It first partitions images into homogeneous areas and edge areas by setting a preset threshold value based on the local structure characteristics, and then specified algorithms are assigned to interpolate each classified areas, respectively. In this way, it achieves the goals of real-time interpolation and good subjective quality. The interpolated images have higher peak signal noise ratios (PSNR) and better visual effects using proposed method than that of using other algorithms referred to in this paper. Experimental results show that proposed method is highly performed in image interpolation.

区域指导的自适应图像插值算法

提出了一种以图像区域的一致性为指导的自适应选择插值公式(简称ADA)的图像插值算法.首先将图像分割成不同区域,然后结合近邻法和众数法确定待插值点所属区域,将待插值点分类处理:对于区域内的点,采用线性插值;对于区域间的过渡点,设计非线性插值公式,分配较大的权值给与待插值点属于同一区域的邻域像素,分配较小的权值给其它邻域像素.实验表明,ADA图像插值算法得到的插值图像有较好的主观图像质量,其峰值信噪比(PSNR)比传统方法平均提高了3.11～4.39 dB.     

一种改进的线性图像插值算法

针对传统的双线性插值法在对图像进行插值后会不可避免的产生边缘模糊的问题,提出了一种改进的线性插值法,该算法首先把待插值点分为三类,然后分别选取合适的已知点进行插值。通过对经典图像lena和pepper进行插值的实验结果表明,该算法的插值效果与双立方法相当,但计算量远远小于双立方,能有效的保持图像边缘信息,提高了图像质量。     

Nonlinear filtering approach to 3-D gray-scale image interpolation

Three-dimensional (3-D) images are now common in radiology. A 3-D image is formed by stacking a contiguous sequence of two-dimensional cross-sectional images, or slices. Typically, the spacing between known slices is greater than the spacing between known points on a slice. Many visualization and image-analysis tasks, however, require the 3-D image to have equal sample spacing in all directions. To meet this requirement, one applies an interpolation technique to the known 3-D image to generate a new uniformly sampled 3-D image. The authors propose a nonlinear-filter-based approach to gray-scale interpolation of 3-D images. The method, referred to as column-fitting interpolation, is reminiscent of the maximum-homogeneity filter used for image enhancement. The authors also draw upon the paradigm of relaxation labeling to devise an improved column-fitting interpolator. Both methods are typically more effective than traditional gray-scale interpolation techniques.     

Generalised approach to parallelising image sequence codingalgorithms

The author describes the parallelisation of three different versions of the CCITT H.261 encoder algorithm using a generalised parallel design methodology based upon pipelines of processor farms (PPFs). For each algorithm, a theoretical upper-bound scaling model was derived by analysing the execution time profile of the algorithm and its feedback structure. The performance predicted by the model was, in each case, in good agreement with that achieved by the corresponding practical implementation. Practical throughput scaling up to a factor of 11 was achieved, using PPFs containing up to 16 processors. The design examples illustrate the impact which feedback has on potential speedup for image coding algorithms, and the diagnostic role of the model in identifying those algorithm components which restrict scaling performance. It is believed that the techniques presented may be useful both in developing embedded image coders based upon multiple DSP devices, and for simulation work with large image sequences in application areas such as image coding for HDTV and SHDTV     

Fuzzy-adapted linear interpolation algorithm for image zooming

This work presents a novel fuzzy linear interpolation algorithm with application in image zooming. Fuzzy logics are employed to derive suitable weights for the neighboring samples in the interpolation formulae. By considering local gradients to calculate the weights, the accuracy of the interpolated value is improved. Additionally, a modification of the proposed algorithm based on the interpolation error theorem is developed to deal with images containing ridges and valleys. Both quantitative results obtained by measuring the peak signal-to-noise ratio (PSNR) and perceptual observations assessed the superior performance of the proposed algorithm and its modified version with respect to the state-of-the-art interpolation methods.     

Efficient interpolation scheme for image sequence data compression

Presents a video coding approach that requires a very low bit rate and achieves good visual quality. The approach allows easy and cheap hardware implementation. Intra- and interframe correlations are fully exploited through a spatio-temporal interpolation applied to a nonuniform 3D grid     

Temporal image sequence prediction using motion field interpolation

A new method for motion-compensated temporal prediction of image sequences is proposed. Motion vector fields in natural scenes should possess two basic properties. First, the field should be smoothly varying within moving objects to compensate for nonrigid or rotational motion, and scaling of objects. Second, the field should be discontinuous along the boundaries of the objects. In the proposed method the motion vector field is modelled using finite element methods and interpolated using adaptive interpolators to satisfy the above-stated requirements. This is particularly important when only very sparse estimates of motion vector fields are available in the decoder due to bit-rate constraints limiting the amount of overhead information that can be transmitted. The proposed prediction method can be applied for low-bit-rate video coding in conventional codecs based on motion-compensated prediction and transform coding, as well as in model-based codecs. The performance of the proposed method is compared with standard motion-compensated prediction based on block matching. It is shown that for simple video telephony scenes a reduction of more than 30% in the energy of the prediction error can be achieved with an unchanged number of transmitted motion vectors and with only a modest increase in computational complexity. When implemented in an H.261 codec the new prediction method can improve the peak SNR 1–2 dB producing a significant visual improvement.     

基于Otsu阈值分割的边缘快速图像插值算法

为了满足视频监控、目标检测与识别过程中较高图像质量和较低算法复杂度要求,以及改善传统图像插值中细节模糊和边缘锯齿效应,文中提出一种基于Otsu阈值分割的边缘快速图像插值算法。利用Otsu算法,根据目标区域和背景区域的类方差最大,确定分割阈值,对非边缘区域进行双线性插值,边缘区域利用与待插值点周围6个或8个相邻降采样像素局部结构的多方向特点,自适应估计高分辨率像素值。实验表明,该算法运算复杂度低,很好保持了图像的边缘,获得了视觉质量较好的高分辨率图像。     

A genetic algorithm approach to a general category projectscheduling problem

A genetic algorithm (GA) approach is proposed for the general resource-constrained project scheduling model, in which activities may be executed in more than one operating mode, and renewable as well as nonrenewable resource constraints exist. Each activity's operation mode has a different duration and requires different amounts of renewable and nonrenewable resources. The objective is the minimization of the project duration or makespan. The problem under consideration is known to be one of the most difficult scheduling problems, and it is hard to find a feasible solution for such a problem, let alone the optimal one. The GA approach described in this paper incorporates problem-specific scheduling knowledge by an indirect chromosome encoding that consists of selected activity operating modes and an ordered set of scheduling rules. The scheduling rules in the chromosome are used in an iterative scheduling algorithm that constructs the schedule resulting from the chromosome. The proposed GA is denoted a hybrid GA (HGA) approach, since it is integrated with traditional scheduling tools and expertise specifically developed for the general resource-constrained project scheduling problem. The results demonstrate that HGA approach produces near-optimal solutions within a reasonable amount of computation time     

A unified approach to optimal image interpolation problems based onlinear partial differential equation models

The unified approach to optimal image interpolation problems presented provides a constructive procedure for finding explicit and closed-form optimal solutions to image interpolation problems when the type of interpolation can be either spatial or temporal-spatial. The unknown image is reconstructed from a finite set of sampled data in such a way that a mean-square error is minimized by first expressing the solution in terms of the reproducing kernel of a related Hilbert space, and then constructing this kernel using the fundamental solution of an induced linear partial differential equation, or the Green's function of the corresponding self-adjoint operator. It is proved that in most cases, closed-form fundamental solutions (or Green's functions) for the corresponding linear partial differential operators can be found in the general image reconstruction problem described by a first- or second-order linear partial differential operator. An efficient method for obtaining the corresponding closed-form fundamental solutions (or Green's functions) of the operators is presented. A computer simulation demonstrates the reconstruction procedure.     

A singular-value decomposition-based image watermarking using genetic algorithm

In this paper, a novel optimal watermarking scheme based on singular-value decomposition (SVD) using genetic algorithm (GA) is presented. The singular values (SVs) of the host image are modified by multiple scaling factors to embed the watermark image. Modifications are optimised using GA to obtain the highest possible robustness without losing the transparency. Experimental results show both the significant improvement in transparency and the robustness under attacks.     

一种基于图像插值的SIFT算法研究

SIFT特征是图像的局部特征,其对旋转,尺度缩放,亮度变化保持不变性,对视角变化、一定角度的仿射变换、噪声也保持一定程度的稳定性.提出了一种具有尺度不变特征转换的图像插值的SIFT算法.首先对图像进行SIFT特征提取,利用K-D树搜索并计算最近邻特征向量与次最近邻向量间的欧式距离来实现对特征点的匹配.在此基础上加入图像插值法增大采集特征点的范围,从而增加特征点匹配的对数.最后比较3种图像插值方法.实验结果表明：双线性插值法获取的特征点匹配的对数最多,但匹配时间较长.     

一种改进的双线性插值图像放大算法

针对传统的双线性插值图像放大算法存在的边缘模糊问题,提出一种改进算法：先计算插值点的双线性插值和最近邻点插值,然后以4个邻点的灰度方差构造权重,将二种插值进行加权融合获得最终插值结果。该算法既考虑到插值点与邻点之间距离关系,又考虑到邻点的灰度分布特性,有效地提高了放大图像的质量。实验结果验证了算法的有效性。     

A Markov random field approach for topology-preserving registration: application to object-based tomographic image interpolation

This paper proposes a topology-preserving multiresolution elastic registration method based on a discrete Markov random field of deformations and a block-matching procedure. The method is applied to the object-based interpolation of tomographic slices. For that purpose, the fidelity of a given deformation to the data is established by a block-matching strategy based on intensity- and gradient-related features, the smoothness of the transformation is favored by an appropriate prior on the field, and the deformation is guaranteed to maintain the topology by imposing some hard constraints on the local configurations of the field. The resulting deformation is defined as the maximum a posteriori configuration. Additionally, the relative influence of the fidelity and smoothness terms is weighted by the unsupervised estimation of the field parameters. In order to obtain an unbiased interpolation result, the registration is performed both in the forward and backward directions, and the resulting transformations are combined by using the local information content of the deformation. The method is applied to magnetic resonance and computed tomography acquisitions of the brain and the torso. Quantitative comparisons offer an overall improvement in performance with respect to related works in the literature. Additionally, the application of the interpolation method to cardiac magnetic resonance images has shown that the removal of any of the main components of the algorithm results in a decrease in performance which has proven to be statistically significant.     

A digital signal processing approach to interpolation

In many digital signal precessing systems, e.g., vacoders, modulation systems, and digital waveform coding systems, it is necessary to alter the sampling rate of a digital signal Thus it is of considerable interest to examine the problem of interpolation of bandlimited signals from the viewpoint of digital signal processing. A frequency dmnain interpretation of the interpolation process, through which it is clear that interpolation is fundamentally a linear filtering process, is presented, An examination of the relative merits of finite duration impulse response (FIR) and infinite duration impulse response (IIR) digital filters as interpolation filters indicates that FIR filters are generally to be preferred for interpolation. It is shown that linear interpolation and classical polynomial interpolation correspond to the use of the FIR interpolation filter. The use of classical interpolation methods in signal processing applications is illustrated by a discussion of FIR interpolation filters derived from the Lagrange interpolation formula. The limitations of these filters lead us to a consideration of optimum FIR filters for interpolation that can be designed using linear programming techniques. Examples are presented to illustrate the significant improvements that are obtained using the optimum filters.     

基于图像插值的大容量可逆水印算法

提出一种基于图像插值的大容量可逆水印算法 。首先,对输入图像进行下采样 处理,利用某种图像插值方法对下采样生成的图像进行插值放大,得到待嵌入水印信号的载 体图像;然后,对载体 图像进行分块,得到每一分块4个基准像素的最大值和最小值,之后计算每一个非基准像素 分别与最大值和最小值 差值的绝对值,根据自适应选定的差值,计算每一个非基准像素能嵌入的最大水印位数;最 后,从待嵌入的水印信 号中将每一个非基准像素能嵌入的位数转换为十进制数,并将此数修改像素值,完成水印 信号的嵌入。大量的仿 真实验结果表明,本文算法不会出现像素值溢出现象,能实现可逆数据隐藏;与相似的基于 图像插值的可逆水印算法 相比,该算法的嵌入率(ER,embedding rate)更高;在相同 的ER条件下,本文算法的性能更好。     

Stereoscopic image interpolation using a spatially variant regularisation approach

This paper studies the problem of stereoscopic image interpolation, where a pair of images with mixed-resolution is given. Specifically, one image yields a low resolution, while the other one yields a higher resolution. The aim of the proposed approach is to reconstruct another pair of images with same high resolutions. To achieve this objective, the proposed approach imposes a regularisation on the reconstructed high-resolution image to perform image interpolation. Furthermore, the degree of regularisation is adaptively adjusted according to the local gradient of the reconstructed high-resolution image. Experiments are conducted to demonstrate that the proposed approach outperforms several conventional image interpolation approaches.     

Memristor-based genetic algorithm for image restoration

This paper explores a way of deploying the classical algorithm named genetic algorithm (GA) with the memristor. The memristor is a type of circuit device with both characteristics of storage and computing, which provides the similarity between electronic devices and biological components, such as neurons, and the structure of the memristor-based array is similar to that of chromosomes in genetics. Besides, it provides the similarity to the image gray-value matrix that can be applied to image restoration with GA. Thus, memristor-based GA is proposed and the experiment about image restoration using memristor-based GA is carried out in this paper. And parameters, such as the size of initial population and the number of iterations, are also set different values in the experiment, which demonstrates the feasibility of implementing GA with memristors.¹