Image normalization for pattern recognition

In general, there are four basic forms of distortion in the recognition of planar patterns: translation, rotation, scaling and skew. In this paper, a normalization algorithm has been developed which transforms pattern into its normal form such that it is invariant to translation, rotation, scaling and skew. After normalization, the recognition can be performed by a simple matching method. In the algorithm, we first compute the covariance matrix of a given pattern. Then we rotate the pattern according to the eigenvectors of the covariance matrix, and scale the pattern along the two eigenvectors according to the eigenvalues to bring the pattern to its most compact form. After the process, the pattern is invariant to translation, scaling and skew. Only the rotation problem remains unsolved. By applying the tensor theory, we find a rotation angle which can make the pattern invariant to rotation. Thus, the resulting pattern is invariant to translation, rotation, scaling and skew. The planar image used in this algorithm may be curved, shaped, a grey-level image or a coloured image, so its applications are wide, including recognition problems about curve, shape, grey-level and coloured patterns. The technique suggested in this paper is easy, does not need much computation, and can serve as a pre-processing step in computer vision applications.     

图像规格化的一种新方法

图像规格化是图像理解系统中的一种常用方法。通常来讲,二维模式有四种失真形式:平移、旋转、伸缩和歪斜。本文提出了一种新的图像规格化方法,该方法对上述四种形式的失真图像都能正确规格化,而已有的规格化算法至多只能处理三种形式的失真。本算法首先计算给定模式的协方差矩阵,然后根据协方差矩阵的特征向量旋转模式,并根据特征值沿特征向量伸缩模式。这时,模式已变换为最紧凑形式。经过上述处理后,结果模式对平移、伸缩和歪斜失真都是不变的。但是,旋转问题没有解决。本算法的最后一步是根据“图像椭圆倾角”旋转图像以使其对旋转变换也保持不变。这样,结果模式对平移、伸缩、旋转和歪斜变换都是不变的。对飞机图像的实验验证了这种新型的图像规格化方法的正确性和有效性。     

Learning class-specific dictionaries for digit recognition from spherical surface of a 3D ball

In the literature, very few researches have addressed the problem of recognizing the digits placed on spherical surfaces, even though digit recognition has already attracted extensive attentions and been attacked from various directions. As a particular example of recognizing this kind of digits, in this paper, we introduce a digit ball detection and recognition system to recognize the digit appearing on a 3D ball. The so-called digit ball is the ball carrying Arabic number on its spherical surface. Our system works under weakly controlled environment to detect and recognize the digit balls for practical application, which requires the system to keep on working without recognition errors in a real-time manner. Two main challenges confront our system, one is how to accurately detect the balls and the other is how to deal with the arbitrary rotation of the balls. For the first one, we develop a novel method to detect the balls appearing in a single image and demonstrate its effectiveness even when the balls are densely placed. To circumvent the other challenge, we use spin image and polar image for the representation of the balls to achieve rotation-invariance advantage. Finally, we adopt a dictionary learning-based method for the recognition task. To evaluate our system, a series of experiments are performed on real-world digit ball images, and the results validate the effectiveness of our system, which achieves 100 % accuracy in the experiments.     

一种数字仪表显示值快速识别方法

提出了一种数字仪表显示值的快速识别方法。该方法首先由计算机自动定位分割图像中的数字区域并实现单个数字的切分,然后对每个数字图像提取了一组具有较高区分度且计算简单的典型特征,最后,基于模糊识别的最大隶属原则,构造了一种数字识别器,实现了仪表显示值的实时识别。试验表明:该方法的识别率高达99%,对7位数字的识别时间不超过20毫秒,并且具有较强的抗干扰能力,达到了仪表显示值识别的速度和准确率要求。     

基于Gauss消元法的车牌图像变形矫正

车辆牌照识别是智能交通系统的重要组成部分,而车牌图像的分割定位与字符提取是车牌识别系统的关键步骤,定位提取效果直接决定了车牌识别系统的工作效率。斜向拍摄的车牌图像存在着透视变形,该情况下直接进行车牌旋转不能有效地矫正,必须进行变形矫正才能准确地提取出各个牌照字符。文中利用双线性空间映射来矫正变形车牌图像,采用高斯消元法来计算该映射方程组的解,从而较好地解决了车牌透视变形的矫正问题,提高了车牌图像变形矫正的运算精度与速度。     

Arabic handwritten digit recognition

In this paper, we fill a gap in the literature by studying the problem of Arabic handwritten digit recognition. The performances of different classification and feature extraction techniques on recognizing Arabic digits are going to be reported to serve as a benchmark for future work on the problem. The performance of well known classifiers and feature extraction techniques will be reported in addition to a novel feature extraction technique we present in this paper that gives a high accuracy and competes with the state-of-the-art techniques. A total of 54 different classifier/features combinations will be evaluated on Arabic digits in terms of accuracy and classification time. The results are analyzed and the problem of the digit ‘0’ is identified with a proposed method to solve it. Moreover, we propose a strategy to select and design an optimal two-stage system out of our study and, hence, we suggest a fast two-stage classification system for Arabic digits which achieves as high accuracy as the highest classifier/features combination but with much less recognition time.     

An MLP-SVM combination architecture for offline handwritten digit recognition

This paper presents an original hybrid MLP-SVM method for unconstrained handwritten digits recognition. Specialized Support Vector Machines (SVMs) are introduced to improve significantly the multilayer perceptron (MLP) performance in local areas around the separating surfaces between each pair of digit classes, in the input pattern space. This hybrid architecture is based on the idea that the correct digit class almost systematically belongs to the two maximum MLP outputs and that some pairs of digit classes constitute the majority of MLP substitutions (errors). Specialized local SVMs are introduced to detect the correct class among these two classification hypotheses. The hybrid MLP-SVM recognizer achieves a recognition rate of 98.01%98.01\% , for real mail zipcode digits recognition task. By introducing a rejection mechanism based on the distances provided by the local SVMs, the error/reject trade-off performance of our recognition system is better than several classifiers reported in recent research.     

Extraction and optimization of B-spline PBD templates forrecognition of connected handwritten digit strings

The recognition of connected handwritten digit strings is a challenging task due mainly to two problems: poor character segmentation and unreliable isolated character recognition. The authors first present a rational B-spline representation of digit templates based on Pixel-to-Boundary Distance (PBD) maps. We then present a neural network approach to extract B-spline PBD templates and an evolutionary algorithm to optimize these templates. In total, 1000 templates (100 templates for each of 10 classes) were extracted from and optimized on 10426 training samples from the NIST Special Database 3. By using these templates, a nearest neighbor classifier can successfully reject 90.7 percent of nondigit patterns while achieving a 96.4 percent correct classification of isolated test digits. When our classifier is applied to the recognition of 4958 connected handwritten digit strings (4555 2-digit, 355 3-digit, and 48 4-digit strings) from the NIST Special Database 3 with a dynamic programming approach, it has a correct classification rate of 82.4 percent with a rejection rate of as low as 0.85 percent. Our classifier compares favorably in terms of correct classification rate and robustness with other classifiers that are tested     

一种改进的模板匹配的数字识别算法

提出了一种改进的模板匹配的数字识别算法,该算法是预先将字符分成若干个集合,经细化得到数字中央的骨骼部分,再对待识别数字提取特征并与训练库中的数字特征加权比较,利用欧式距离最小原则来对数字作出判决,试验结果表明,加权的模板匹配法保证了数字识别的正确率,而对数字进行预分类和细化处理,可以大大缩小模板匹配的识别速度,弥补了模板匹配算法对于大量数字耗时多的缺点,提升了系统速度。     

基于DM642的手机QR码检测与识别

基于市场上二维条码设备的广泛需求,研究了基于DM642的QR码的检测与识别技术.本文针对嵌入式智能设备获取的QR码（Quick Response Code,QR）图像严重倾斜与高度畸变问题,提出了基于位置探测图形的轮廓嵌套特性与轮廓之间面积比例关系来实现QR码定位的算法,接着以直线逼近的方法精确定位QR码的4个角点,然后运用逆透视变换与旋转校正的原理实现QR码的复原操作,最后基于复原后的图像通过网格采样来获取整个二维码的“01”矩阵,以便于后面的QR码解码.最终将算法移植到DM642上运行,能有效解决图像倾斜与畸变问题且解码效果良好.     

信息检索方法在手写数字识别中的应用及改进

本文首先将文本信息检索中LSI方法的思想和原理应用于手写数字识别问题,把手写数字图像看作空间向量的表示,通过计算未知数字与各训练集之间相关度排序来达到识别的目的,计算量小且有较低的误识率(5.5%);其次,通过对所有0-9数字的训练样本排列为一个矩阵,并对该矩阵进行奇异值分解,将各训练样本在适当维数的左奇异向量上分别投影,得到了一种低阶表示下的相关度计算方法,该方法在保持原有较低误识率的同时,能极大地压缩原有训练样本数据(压缩掉的数据百分比超过95%);另外,利用了区分不规范样本的思想,获得了更低的误识率(下降到4.5%)。     

基于决策树的快速在线手写数字识别技术

本文提出了一种快速的在线手写数字识别方法，该法采用书写笔划走势对手写数字进行建模，运用决策树学习算法进行数字分类识别。数字笔划走势特征提取简单、区分度高、对用户不敏感，实现了有限的资源条件下的高速识别，同时保证了方法的良好用户适应性；决策树学习算法分类情况全面，保证了方法的高识别率。实验结果表明：该方法既具有简单高效的特点，又具备很好的用户适应性。     

手写体数字有效鉴别特征的抽取与识别

文中提出了基于后验概率估计的多特征多分类器组合识别的估计法,并提出了基于具有统计不相关性的最佳鉴别变换与ＫＬ变换抽取手写体数字的有效鉴别特征的方法。实验采用Ｃｏｎｃｏｒｄｉａ Ｕｎｉｖｅｒｓｉｔｙ ＣＥＮＰＡＲＭＩ手写体数字数据库。用最近邻距离分类器与最近邻相关分类器这两个分类器,对手写体数字的１２个特征做多特征多分类器组合识别实验。实验结果表明：估计法优于常用的投票法与计分法,估计法的识别率高达     

自适应三维形变模型结合流形分析的人脸识别方法

为了在人脸姿态和表情归一化后减少人脸外观的信息损失,提出自适应三维形变模型(3DMM)结合流形分析的人脸识别方法。首先,描述人脸姿态变换引起的2D和3D坐标的不对应性,提出自适应3DMM拟合方法;然后,通过三维变换来保留尽可能多的身份信息,将整个图像网格化映射成3D对象,姿态和表情的归一化保证了变换的稳定;最后,利用多流形判别分析计算流形与流形之间的距离,并利用最近邻分类器完成识别。在Multi-PIE,LFW以及自己采集的数据库上的实验验证了所提方法的有效性,在3个数据库上的识别率分别高达99.8%,95.25%,98.62%。所提方法显著改善了人脸识别性能,在约束和无约束环境下均优于其他几种较新的识别方法。     

汉语连续数字串识别的改进

介绍了利用三音子模型和基频信息提高汉语连续数字串的识别率。在汉语连续数字串识别中“8”和“2”是容易混淆的数字,而“9”和“6”在识别时会在末尾插入一个“5”而变成“95”和“65”。三音子模型将不同上下文的同一个数字区分开来,明显提高了识别率。基频反映了声调的变化,将它们作为后处理进一步降低了错误率。     

基于模板匹配的联机手写数字识别

在深入学习和研究模板匹配分类理论和模式识别的过程基础上.利用模板匹配分类算法设计了一个图像分类器.该分类器通过对待分类样本与训练集中的样本之间距离的计算.对0～9这十类联机手写数字图像进行分类识别.     

纹理图象亮度阈值法提取SAR图象居民地

由于微波辐射的复杂特性，从合成孔径雷达图象上提取类似于居民地复杂结构的目标物的研究仍处于探索中．通过研究居民地对合成孔径雷达(SAR)的微波散射特性，分析居民地在SAR图象上的纹理特征，综合利用纹理分析、模式识别和颜色空间变换技术，提出了一种新的提取雷达图象上居民地的方法．该方法在共生矩阵纹理分析的基础上，选取3个合适的特征分量合成彩色纹理特征图象，再通过HIS变换获得亮度分量，使用亮度阈值分割图象来提取出居民地．此方法的特点是，其受雷达系统影响较小，适应性较强，以二值图象的形式记录居民地的提取结果．试验表明，利用此方法在SAR图象上提取居民地具有70％以上的正确识别率．     

基于旋转投影统计特征的手写数字识别方法

通过抽取数字的轮廓和骨架来提取几何特征,可以有效地反映手写数字的细节,但手写数字的不规范性导致其识别率并不高。运用统计分析理论可以克服这一缺点。首先提出了基于投影间隔比率和间隔变化的特征提取方法,通过数字投影计算间隔的像素数比率和变化趋势,并将其归一化作为特征向量。进一步通过旋转投影基准线,增加特征向量之间的正交性以减少信息冗余,基于这一思路提出旋转投影的识别方法。理论分析和实验证明了旋转投影可以在相同特征数量的情况下达到更高的识别率,并给出了推荐参数。此外,通过旋转投影,直接解决了倾抖数字的识别问题。     

Gabor相位特征的人脸光照不变量提取

为了消除光照变化对人脸识别的影响,提出一种基于Gabor相位特征的光照不变量提取算法。该算法首先对图像进行光照归一化,一定程度上减弱了不同光照条件的影响;然后利用一组不同方向的2维实Gabor小波对图像进行变换,在兼顾频谱与相位信息的情况下组合变换后的Gabor系数,提取其相位特征,得到光照不变量。在Yale B和CMU PIE人脸库上的实验结果表明,该算法能够有效消除光照变化对人脸识别的影响,提取的光照不变量具有一定的鲁棒性。     

Segmentation and recognition system for unknown-length handwritten digit strings

The segmentation of handwritten digit strings into isolated digits remains a challenging task. The difficulty for recognizing handwritten digit strings is related to several factors such as sloping, overlapping, connecting and unknown length of the digit string. Hence, this paper aims to propose a segmentation and recognition system for unknown-length handwritten digit strings by combining several explicit segmentation methods depending on the configuration link between digits. Three segmentation methods are combined based on histogram of the vertical projection, the contour analysis and the sliding window Radon transform. A recognition and verification module based on support vector machine classifiers allows analyzing and deciding the rejection or acceptance each segmented digit image. Moreover, various submodules are included leading to enhance the robustness of the proposed system. Experimental results conducted on the benchmark dataset show that the proposed system is effective for segmenting handwritten digit strings without prior knowledge of their length comparatively to the state of the art.