基于相对链码和改进 LCS 算法的图形匹配实现

研究相对链码和字符串的匹配算法,采用相对链码和改进的LCS算法实现图形的轮廓匹配。首先通过轮廓提取算法得到图形的轮廓,再通过轮廓跟踪算法得到轮廓的链码,由链码计算得到图形的相对链码,最后采用改进的最大公共子串算法计算两图形的相似度。该图形轮廓匹配算法具有计算量小,平移、旋转的不变性等优点。在Android系统上进行实验,实验结果表明该算法计算速度快,与人的视觉相吻合。     

二值图像中拐点的实时检测算法

鉴于数字图像中的拐点通常成为重要的信息载体,因此准确、稳定和实时地检测出拐点便成为拐点检测算法面临的主要问题,针对该问题,提出了一种新的二值图像中拐点的实时检测算法。该算法与传统基于边界链码的拐点检测算法不同,其是首先构建像素的k(k>8)邻域,并将图像中物体的边界表示为k邻域链码;然后根据曲率定义的差分形式计算各边界点处的曲率;最后通过检测曲率直方图的局部峰值精确定位出拐点,并利用拐角内部像素的颜色统计信息迅速判断出拐点的凸凹性.为验证该算法的效果,给出了该算法与4种已有算法的对比实验.结果表明,该算法不仅稳定性、准确性较高,而且算法简单,实时性强,并适合于嵌入式计算环境。     

Restoration of binary images using contour direction chain codes description

A binary image can be described by using one or several direction chain codes which record the contour of this binary image. According to the chain codes mentioned, a simple algorithm for getting the original image is given in this paper.     

Encoding of line drawings with a multiple grid chain code

The multiple grid(MG) chain code which uses four different square grids is proposed to encode line drawings. The main processes adopted in the code are: 1) a grid selection algorithm which allocates quantization points only to the vicinity of the course of a line drawing, 2) labeling rule on quantization points which makes the frequency of some codes larger than that of other codes, and 3) quantization points allocation-not to the corners, but to the sides of a square which makes the straight line segments larger without increasing quantization error. A performance comparison of various chain codes is made from the viewpoints of the encoding efficiency, naturalness of the encoded lines, and the rate distortion measure. Also, the superiority of the MG chain code to other codes is shown. At last, application of the MG chain code to the electronic blackboard system is explained.     

Parallel,overlapped, and intersected digital straight lines

A digital straight line is represented by a chain code of directions which satisfy Freeman's three criteria. Given two chain codes of digital straight lines and their starting pixels where their equations are not known, the paper will describe how to determine if they are parallel, overlapped, or intersected. An algorithm with only integer arithmetic is also implemented to find the intersection.     

矩形点阵上八近邻图像的链码转换算法

给出了矩形点阵上八近邻图像的顶点链码（VCC）、Freeman链码和边界链码之间的转换算法，给出了图像边界的边界链码与顶点链码之间的相互转化算法和顶点链码与Freeman链码之间的相互转换算法，于是可以方便地直接由一种链码得到其他的链码表示，由某种链码获得的图像信息也为其他链码所共享．     

矩形点阵上链码的转换算法

链码是图像处理和图像识别中的一个重要工具.给出了四近邻图像的顶点链码（VCC）、Freeman链码和边界链码之间的转换算法,这样只要获得一种链码就可以得到其它的链码表示,由某种链码获得的图像信息也为其他链码所共享.     

A new chain-coding algorithm for binary images using run-length codes

This paper presents a new algorithm for converting a binary image into chain codes using its run-length codes. The basic idea of conventional chain-coding algorithm is to follow boundary pixels by convolving a 3 × 3 window with the image and to sequentially generate chain codes. The proposed algorithm has two phases, namely run-length coding and chain-code generation. We use connectivity information between runs as well as their coordinates in the phase of run-length coding. In the second phase (chain-code generation) the connectivity information extracted in the first phase is utilized for sequentially tracking runs containing the boundary pixels to be followed. This algorithm has an advantage that we can detect easily the inclusion relationship between boundaries at the same time as chain-code generation.     

数字图像中基于链码的目标面积计算方法

在数字图像处理领域,链码是一种极其有效的目标描述方式,基于链码描述的面积计算得到了广泛的应用。该文分析了现有的多种基于链码的面积计算方法,对它们在算法原理、速度和精度方面进行了分析和比较,并通过实验给出了适合小目标的面积计算方法。     

基于隐写编码和Markov模型的自适应图像隐写算法

如何构造大容量、低失真和高统计安全的隐写算法一直是隐写研究的难点和热点.提出一种兼顾感知失真和二阶统计安全的自适应图像隐写算法设计思路.算法将载体各部分的平滑度引入隐写编码的生成过程,自适应地利用一簇隐写编码在载体各部分的合理运用降低载密图像失真度;在隐秘信息嵌入方式上利用基于Markov链模型的动态补偿方法提高载密图像统计安全性;算法对载体最低有效位和次最低有效位进行嵌入以保证嵌入容量.实验表明算法在相同嵌入量下相较双层随机LSB匹配算法以及仅使用一种隐写编码的算法,失真度更低且载体统计分布的改变更小,而在失真度和统计分布改变相近时嵌入容量更大.     

A parallel algorithm for generating chain code of objects in binary images

This paper addresses parallel execution of chain code generation on a linear array architecture. The contours in the proposed algorithm are viewed as a set of edges (or contour segments) that can be traced by a top-down contour tracing method to generate the chain codes for the outer and inner object contours. A parallel algorithm that contains the chain code generating rules and operations needed is also described, and the algorithm is mapped onto a one-dimensional systolic array containing processing elements (PEs) to devise this architecture. The architecture extracts the contours of objects and quickly generates the corresponding chain codes after the image data in all rows are inputted in a linear fashion. The total processing time for generating the chain codes in an N×N image is O(3N). By doing so, the real-time requirement is fulfilled and its execution time is independent of the image content. In addition, a partition method is developed to process an image when the parallel architecture has a fixed number of PEs; say two or more. The total execution time for an N×N image by employing a fixed number of PEs is N(N+1)/M+2(M−1), when M is the fixed number of PEs.     

基于手机平台的Data Matrix 2维条码识别

传统的条码图像采集和识别是通过工业扫描枪。近年来,随着移动增值业务和3G技术的发展,2维条码在手机设备的应用中得到飞速发展。以Data Matrix为例,研究了基于嵌入式手机设备的2维条码识别技术。首先根据Data Matrix条码的特点,给出了一种基于链码跟踪和线段检测的快速Data Matrix检测算法。接着分析了条码信号经过点扩展函数卷积后的降质模型,并利用维纳滤波对条码信号进行反模糊滤波。最后,针对透视畸变的现象,设计了一种适合于嵌入式手机设备的快速反透视算法。实验结果表明,提出的识别算法具有优秀的性能,显著提高了条码的识别率,满足了实际使用的要求。     

A simple algorithm for detection of significant vertices for polygonal approximation of chain-coded curves

A simple but efficient method is proposed for detection of significant points of chain-coded curves. The polygonal approximation is achieved by joining successive significant vertices. The algorithm is based on manipulation with chain codes only.     

Decoding algorithms for shortened-extended turbo product codes in WiMAX systems

The component codes of turbo product codes inWiMAX systems are extended Hamming codes and single parity check codes as well as their shortened forms. In this paper, three novel iterative decoding algorithms based on Chase, MAP algorithms and their combination are proposed for shortened-extended turbo product codes. The iterative decoding algorithm based on Chase algorithm is proposed to reduce the decoding complexity without any performance loss. An efficient MAP algorithm is then proposed to decode the component codes of shortened single parity check codes and shortened-extended Hamming codes. A comprehensive performance comparison of the proposed decoding schemes is conducted for three typical classes of turbo product codes in WiMAX OFDMA systems. The suitable decoding algorithms are recommended for different classes based on the simulation results.     

基于链码的人脸表情几何特征提取

已有人脸表情特征提取算法的表情识别率较低.为此,提出一种基于链码的人脸表情几何特征提取算法.以主动形状模型特征点定位为基础,对面部目标上定位的特征点位置进行循环链码编码,以提取出人脸表情几何特征.实验结果表明,相比经典的LBP表情特征鉴别方法,该算法的识别率提高约10％.     

Tree searched chain coding for subpixel reconstruction of planarcurves

Coding schemes for the quantization of line drawings that outperform basic chain codes are investigated. First, subpixel accuracy reconstruction is obtained by a simple linear filtering of the chain code points, which achieves a factor-of-three to-four reduction in average reconstruction distortion for smooth curves. Second, the basic chain encoding schemes are generalized to a multipath-tree-searched encoding scheme. A variation of the (M,L)-algorithm is used to maintain M contending chain code paths in storage and choose the best path from these. Over a wide variety of source curves, tree-searched chain coding results in nearly an order of magnitude reduction in average reconstruction distortion over smoother chain codes. The performance improvement for curves is obtained with only a slight increase in bit rate over basic chain codes     

基于链码检测的直线段检测方法

直线是图像的重要特征，直线参数是进行图像识别和直线段三维重建的重要基础数据。基于链码检测的直线段的检测方法分为4步：以边缘图像为基础进行链码检测；根据链码估计曲率，检测链码角点，并在角点处拆分链码；通过链码直方图检测直线链码；对直线链码进行直线参数估计，并根据连接准则，进行直线连接。实验证明，该方法可以对直线段进行有效的检测。     

基于链码的分水岭变换算法

为了快速准确地进行图像分割，通过对现有分水岭变换算法的分析，并借鉴图像处理中常用的链码思想，提出了基于链码的分水岭变换算法，并首先扩展了传统链码的定义，将其分为指出链码和指入链码；然后提出并阐述了利用链码实现分水岭变换的两个性质；最后给出了基于链码的分水岭变换算法的具体描述，并详细分析了新算法的时间和空间复杂度。实验结果表明，新算法具有较低的时间和空间复杂度，且变换结果更有利于后续的图像理解。     

可变码长LDPC码的GAU构造算法

考虑度分布、最小环长和环近似外信息度等因素,从减少短环和增加外信息度入手,提出了可变码长LDPC码的GAU(Girth ACE union)构造算法。该算法构造的校验矩阵能适应较大范围的码长变化,其短码的纠错性能与802.16e中的LDPC码相当,中长码的性能较后者略优。不同码长的码字具有结构相同的校验矩阵,便于编译码器对所有码长采用同一架构设计,能有效降低编译码器的实现复杂度。GA U算法适用于支持可变长度数据传输的各类通信系统的LDPC码设计,具有重要的理论意义和 实用价值。     

Single chains to represent groups of objects

A chain code is a common, compact and size-efficient way to represent the contour shape of an object. When a group of objects is studied using chain codes, previous works require to obtain one chain code for each object. In this paper we assign a single chain to a group of objects, in such a way that all the properties of each object of the group can be recovered from the single chain. In order to achieve higher levels of compression, we propose a lossless method, that consists of representing a group of objects by means of a single chain, and then to apply a context-mixing algorithm. Regarding other methods of compression of the state-of-the-art, our experiments demonstrate that the best compression performance is achieved when our lossless method is applied. In this case more than 15% of a better compression level is reached.