基于多例学习的Web图像聚类

在图像分类和自动标注系统中,多例学习(MIL)是研究的热点.目前MIL中的算法多为监督学习方法.针对非监督学习,在基于EM算法和启发式迭代优化算法的框架下,提出了6种多例聚类算法,并通过它们对来自于真实Web环境下的图像进行聚类以分析用户的搜索兴趣.由于一幅图像含有若干个区域,每个区域可被看为一个样例,属于同一个图像的区域则组成一个包.因此如何理解图像语义内容的问题即转化为多例学习.在多例学习的经典数据集MUSK数据和来自于Web图像集上的比较实验表明,提出的多例聚类算法具有优良的聚类性能.     

自动图像标注技术研究进展

近年来,自动图像标注(Automatic Image Annotation,AIA)技术已经成为图像语义理解研究领域的热点。其基本思想是利用已标注图像集或其他可获得的信息自动学习语义概念空间与视觉特征空间的潜在关联或者映射关系,来预测未知图像的标注。随着机器学习理论的不断发展,包括相关模型、分类器模型等不同的学习模型已经被广泛地应用于自动图像标注研究领域。现有的自动图像标注算法可以大致分为基于分类的标注算法、基于概率关联模型的标注算法以及基于图学习的标注算法等三大类。首先根据自动图像标注算法的特征提取及表示机制不同,将现有算法划分为基于全局特征和基于区域划分的自动图像标注方法。其次,在基于区域划分的自动图像标注算法中,按照学习算法的不同,将其划分为基于分类的标注方法、基于概率关联模型的标注方法以及基于图学习的标注方法,并分别介绍各类别中具有代表性的标注算法及其优缺点。然后给出了自动图像标注最新的研究进展,最后探讨自动图像标注的进一步研究方向。     

基于集成分类算法的自动图像标注

基于语义的图像检索技术中,按照图像的语义进行自动标注是一个具有挑战性的工作. 本文把图像的自动标注过程转化为图像分类的过程,通过有监督学习对每个图像区域分类并得到相应关键字,实现标注. 采用一种快速随机森林(Fast random forest, FRF)集成分类算法,它可以对大量的训练数据进行有效的分类和标注. 在基于Corel数据集的实验中,相比经典算法, FRF改善了运算速度,并且分类精度保持稳定. 在图像标注方面有很好的应用.     

基于概念索引的图像自动标注

在基于内容的图像检索中,建立图像底层视觉特征与高层语义的联系是个难题.一个新的解决方法是按照图像的语义内容进行自动标注.为了缩小语义差距,采用基于支持向量机(SVM)的多类分类器为空间映射方法,将图像的底层特征映射为具有一定高层语义的模型特征以实现概念索引,使用的模型特征为多类分类的结果以概率形式组合而成.在模型特征组成的空间中,再使用核函数方法对关键词进行了概率估计,从而提供概念化的图像标注以用于检索.实验表明,与底层特征相比,使用模型特征进行自动标注的结果F度量相对提高14%.     

基于判别模型与生成模型的层叠图像自动标注

图像自动标注是模式识别与计算机视觉等领域中重要而又具有挑战性的问题.针对现有模型存在数据利用率低与易受正负样本不平衡影响等问题,提出了基于判别模型与生成模型的新型层叠图像自动标注模型.该模型第一层利用判别模型对未标注图像进行主题标注,获得相应的相关图像集;第二层利用提出的面向关键词的方法建立图像与关键词之间的联系,并使用提出的迭代算法分别对语义关键词与相关图像进行扩展;最后利用生成模型与扩展的相关图像集对未标注图像进行详细标注.该模型综合了判别模型与生成模型的优点,通过利用较少的相关训练图像来获得更好的标注结果.在Corel 5K图像库上进行的实验验证了该模型的有效性.     

BP神经网络在图像语义自动标注的应用

由于传统的基于内容图像检索存在的语义鸿沟问题,其在某些特定的领域无法满足用户的需求。图像语义自动标注的出现能够有效地解决这方面的问题。该文提出了先使用Normalized Cuts方法对图像进行区域分割并提取出每个区域的低层视觉特征,再利用BP神经网络算法来学习图像区域和标注字的对应关系来进行图像语义的自动标注的方法,实验结果证明了此方法的有效性和准确性。     

基于语义分类的文物图像标注研究

由于图像数据中普遍存在的“语义鸿沟”问题,传统的基于内容的图像检索技术对于数字图书馆中的图像检索往往力不从心。而图像标注能有效地弥补语义的缺失。文中分析了图像语义标注的现状以及存在的问题,提出了基于语义分类的文物语义标注方法。算法首先通过构建一个Bayes语义分类器对待标注图像进行语义分类,进而通过在语义类内部建立基于统计的标注模型,实现了图像的语义标注。在针对文物图像进行标注的实验中,该方法获得了较好的标注准确率和效率。     

图像自动标注技术研究进展

现有图像自动标注技术算法可以大致划分为基于语义的标注算法、基于矩阵分解的标注算法、基于概率的标注算法以及基于图学习的标注算法等四大类。介绍了各类别中具有代表性的图像自动标注算法,分析了这些算法的问题模型及其功能特点,并归纳了图像自动标注算法中主要的优化求解方法及算法评价中常用的图像数据集和性能评价指标。最后,指出了图像自动标注技术目前存在的主要问题,并且提出了这些问题的解决思路。分析结果表明,对于图像自动标注技术的研究,可充分利用现有算法的优势互补,或借助多学科交叉的优势,寻找更有效的算法。     

基于语义分类的文物图像标注研究

由于图像数据中普遍存在的“语义鸿沟”问题，传统的基于内容的图像检索技术对于数字图书馆中的图像检索往往力不从心。而图像标注能有效地弥补语义的缺失。文中分析了图像语义标注的现状以及存在的问题，提出了基于语义分类的文物语义标注方法。算法首先通过构建一个Bayes语义分类器对待标注图像进行语义分类，进而通过在语义类内部建立基于统计的标注模型，实现了图像的语义标注。在针对文物图像进行标注的实验中，该方法获得了较好的标注准确率和效率。     

Transductive Multi-Instance Multi-Label learning algorithm with application to automatic image annotation

Automatic image annotation has emerged as an important research topic due to its potential application on both image understanding and web image search. Due to the inherent ambiguity of image-label mapping and the scarcity of training examples, the annotation task has become a challenge to systematically develop robust annotation models with better performance. From the perspective of machine learning, the annotation task fits both multi-instance and multi-label learning framework due to the fact that an image is usually described by multiple semantic labels (keywords) and these labels are often highly related to respective regions rather than the entire image. In this paper, we propose an improved Transductive Multi-Instance Multi-Label (TMIML) learning framework, which aims at taking full advantage of both labeled and unlabeled data to address the annotation problem. The experiments over the well known Corel 5000 data set demonstrate that the proposed method is beneficial in the image annotation task and outperforms most existing image annotation algorithms.     

A review on the application of structured sparse representation at image annotation

The increasing number of images on the Web and other information environments, needs efficient management and suitable retrieval especially by computers. Image annotation is a process which produces words for a digital image based on its content. Users prefer an image search based on text queries and keywords which has increased the use of image annotation. In this paper, we discuss the applicability of structured sparse representations at image annotation. First the components of image annotation and sparse representation are reviewed. Then, we survey the structure of sparse representation based on the image annotation algorithms. Next, the comparison of algorithm has been presented. Finally the paper concludes with some major challenges and open issues in image annotation using structured sparse representations.     

一种基于支持向量机和半监督期望最大化算法的分级图像标识方法

自动图像标识就是自动识别图像中的有意义目标并赋予其相应的语义关键词, 该过程虽然对于人类来说并不难, 但是对于计算机而言却是一项艰巨而有挑战性的任务. 鉴于人类识别物体通常是一个由粗到细的过程, 本文提出一种层次标识方案. 首先, 输入图像被自动分割成多个区域, 每个区域由支持向量机进行粗分类. 由于粗分类结果会直接影响后续细分类, 本文建立统计的上下文语义关系以修订不正确的粗标识. 接着为了对每个获得粗标识的区域进行细分类, 本文提出一种半监督期望最大化算法, 该算法不仅能为每一粗类别下的细类找到代表模式, 而且能对粗分类区域进行二次分类, 使其获得细标识. 最后我们再次应用上下文语义关系修订不合适的细标识. 为了证明上述识别方案的有效性, 我们开发了一个原型图像标识系统, 实验结果证明该层次标识方案是有效的.     

Image modeling with combined optimization techniques for image semantic annotation

Image semantic annotation can be viewed as a multi-class classification problem, which maps image features to semantic class labels, through the procedures of image modeling and image semantic mapping. Bayesian classifier is usually adopted for image semantic annotation which classifies image features into class labels. In order to improve the accuracy and efficiency of classifier in image annotation, we propose a combined optimization method which incorporates affinity propagation algorithm, optimizing training data algorithm, and modeling prior distribution with Gaussian mixture model to build Bayesian classifier. The experiment results illustrate that the classifier performance is improved for image semantic annotation with proposed method.     

Recognition of attentive objects with a concept association network for image annotation

With the advancement of imaging techniques and IT technologies, image retrieval has become a bottle neck. The key for efficient and effective image retrieval is by a text-based approach in which automatic image annotation is a critical task. As an important issue, the metadata of the annotation, i.e., the basic unit of an image to be labeled, has not been fully studied. A habitual way is to label the segments which are produced by a segmentation algorithm. However, after a segmentation process an object has often been broken into pieces, which not only produces noise for annotation but also increases the complexity of the model. We adopt an attention-driven image interpretation method to extract attentive objects from an over-segmented image and use the attentive objects for annotation. By such doing, the basic unit of annotation has been upgraded from segments to attentive objects. Visual classifiers are trained and a concept association network (CAN) is constructed for object recognition. A CAN consists of a number of concept nodes in which each node is a trained neural network (visual classifier) to recognize a single object. The nodes are connected through their correlation links forming a network. Given that an image contains several unknown attentive objects, all the nodes in CAN generate their own responses which propagate to other nodes through the network simultaneously. For a combination of nodes under investigation, these loopy propagations can be characterized by a linear system. The response of a combination of nodes can be obtained by solving the linear system. Therefore, the annotation problem is converted into finding out the node combination with the maximum response. Annotation experiments show a better accuracy of attentive objects over segments and that the concept association network improves annotation performance.     

Image auto-annotation with automatic selection of the annotation length

Developing a satisfactory and effective method for auto-annotating images that works under general conditions is a challenging task. The advantages of such a system would be manifold: it can be used to annotate existing, large databases of images, rendering them accessible to text search engines; or it can be used as core for image retrieval based on a query image’s visual content. Manual annotation of images is a difficult, tedious and time consuming task. Furthermore, manual annotations tend to show great inter-person variance: considering an image, the opinions about what elements are significant and deserve an annotation vary strongly. The latter poses a problem for the evaluation of an automatic method, as an annotation’s correctness is greatly subjective. In this paper we present an automatic method for annotating images, which addresses one of the existing methods’ major limitation, namely a fixed annotation length. The proposed method, PATSI, automatically chooses the resulting annotation’s length for each query image. It is held as simple as possible and a build-in parameter optimization procedure renders PATSI de-facto parameter free. Finally, PATSI is evaluated on standard datasets, outperforming various state-of-the-art methods.     

图像语义自动标注及其粒度分析方法

缩小图像低层视觉特征与高层语义之间的鸿沟, 以提高图像语义自动标注的精度, 进而快速满足用户检索图像的需求,一直是图像语义自动标注研究的关键. 粒度分析方法是一种层次的、重要的数据分析方法, 为复杂问题的求解提供了新的思路. 图像理解与分析的粒度不同, 图像语义标注的精度则不同, 检索的效率及准确度也就不同. 本文对目前图像语义自动标注模型的方法进行综述和分析, 阐述了粒度分析方法的思想、模型及其在图像语义标注过程中的应用, 探索了以粒度分析为基础的图像语义自动标注方法并给出进一步的研究方向.     

融入类别信息的图像标注概率主题模型

基于概率主题模型的图像标注方法旨在通过学习图像语义进行图像标注,近年来倍受研究人员关注。考虑到类别对图像标注可提供有价值的信息,例如,“高楼”类图像,出现“天空”、“摩天楼”的可能性大于“海水”和“沙滩”。而“海岸”类图像出现“海水”、“沙滩”的可能性要大于“天空”和“摩天楼”。在Corr-LDA模型的基础上利用图像类别来改进图像的标注性能,提出了一个融入类别信息的图像标注概率主题模型。为该模型推导了一个基于变分EM的参数估计算法,并给出了使用该模型标注图像的方法。在LabelMe和UIUC-Sport两个真实数据集上验证了提出模型的标注性能要高于其他相比较模型。     

Support vector description of clusters for content-based image annotation

Continual progress in the fields of computer vision and machine learning has provided opportunities to develop automatic tools for tagging images; this facilitates searching and retrieving. However, due to the complexity of real-world image systems, effective and efficient image annotation is still a challenging problem. In this paper, we present an annotation technique based on the use of image content and word correlations. Clusters of images with manually tagged words are used as training instances. Images within each cluster are modeled using a kernel method, in which the image vectors are mapped to a higher-dimensional space and the vectors identified as support vectors are used to describe the cluster. To measure the extent of the association between an image and a model described by support vectors, the distance from the image to the model is computed. A closer distance indicates a stronger association. Moreover, word-to-word correlations are also considered in the annotation framework. To tag an image, the system predicts the annotation words by using the distances from the image to the models and the word-to-word correlations in a unified probabilistic framework. Simulated experiments were conducted on three benchmark image data sets. The results demonstrate the performance of the proposed technique, and compare it to the performance of other recently reported techniques.