Similarity retrieval of iconic image database

The perception of spatial relationships among objects in a picture is one of the important selection criteria to discriminate and retrieve the images in an iconic image database system. The data structure called 2D string, proposed by Chang et al., is adopted to represent symbolic pictures. The 2D string preserves the objects' spatial knowledge embedded in images. Since spatial relationship is a fuzzy concept, the capability of similarity retrieval for the retrieval by subpicture is essential. In this paper, similarity measure based on 2D string longest common subsequence is defined. The algorithm for similarity retrieval is also proposed. Similarity retrieval provides the iconic image database with the distinguishing function different from a conventional database.     

A fractal-based clustering approach in large visual database systems

Large visual database systems require effective and efficient ways of indexing and accessing visual data on the basis of content. In this process, significant features must first be extracted from image data in their pixel format. These features must then be classified and indexed to assist efficient access to image content. With the large volume of visual data stored in a visual database, image classification is a critical step to achieve efficient indexing and retrieval. In this paper, we investigate an effective approach to the clustering of image data based on the technique of fractal image coding, a method first introduced in conjunction with fractal image compression technique. A joint fractal coding technique, applicable to pairs of images, is used to determine the degree of their similarity. Images in a visual database can be categorized in clusters on the basis of their similarity to a set of iconic images. Classification metrics are proposed for the measurement of the extent of similarity among images. By experimenting on a large set of texture and natural images, we demonstrate the applicability of these metrics and the proposed clustering technique to various visual database applications.     

基于颜色空间分布特征的图像检索

目前,基于颜色特征的图像检索大多是以图像的颜色直方图作为颜色特征,这种图像检索方法有简单高效的优点,但丢失了颜色的空间分布信息,该文从CT图像重建的理论中得到启发,将对一幅图像从几个方向的投影图作为这幅图像的颜色特征分布。为进一步减少检索时运算的数据量,对图像做小波分解,然后对分解后图像的低频子带做Radon变换得到颜色空间分布的特征向量,并根据这个特征进行检索,实验表明,当检索图像中有明显的颜色目标时,该方法比传统的颜色直方图法更精确,颜色空间性更强,而且检索用时更短。     

Image database design based on 9D-SPA representation for spatial relations

Spatial relationships between objects are important features for designing a content-based image retrieval system. We propose a new scheme, called 9D-SPA representation, for encoding the spatial relations in an image. With this representation, important functions of intelligent image database systems such as visualization, browsing, spatial reasoning, iconic indexing, and similarity retrieval can be easily achieved. The capability of discriminating images based on 9D-SPA representation is much more powerful than any spatial representation method based on minimum bounding rectangles or centroids of objects. The similarity measures using 9D-SPA representation provide a wide range of fuzzy matching capability in similarity retrieval to meet different user's requirements. Experimental results showed that our system is very effective in terms of recall and precision. In addition, the 9D-SPA representation can be incorporated into a two-level index structure to help reduce the search space of each query processing. The experimental results also demonstrated that, on average, only 0.1254 percent /spl sim/ 1.6829 percent of symbolic pictures (depending on various degrees of similarity) were accessed per query in an image database containing 50,000 symbolic pictures.     

Archival image indexing with connectivity features using randomized masks

Connectivity properties capture a natural spatial feature of a binary image. Albeit they are easy to compute, more often than not, they alone fail to provide a good characterization of the image because of the fact that several different images may have the same connectivity features. Typically, other types of parameters, e.g., moments, are used to augment the connectivity feature for efficient indexing and retrieval purposes. In this work, an alternative approach is proposed. Instead of considering other diverse features, which are computationally intensive, only the connectivity features of the image are used iteratively using a novel concept of spatial masking. For this purpose, a greedy algorithm for constructing a spatial feature vector of variable length for a binary image, is proposed. The algorithm is based on XOR-ing the image bit-plane with a few pseudo-random synthetic masks, and its novelty lies in computing the feature vector iteratively, depending on the size and diversity of the image database. The classical Euler number and the two primary connectivity features from which it is derived, namely, the number of connected components and the number of holes, are used to finally generate a unique feature vector for each binary image in the database using a fuzzy membership function customized for the given database. The method is particularly suitable for large-sized image archives of a digital library, where each image contains one or more objects. It is found to converge within only three iterations for a postal stamp database consisting of 2598 images, and also for a logo database of 1034 images. A data structure called discrimination tree has been introduced for supporting efficient storage and indexing of the images using the above feature vector.     

A knowledge-based approach for retrieving images by content

A knowledge based approach is introduced for retrieving images by content. It supports the answering of conceptual image queries involving similar-to predicates, spatial semantic operators, and references to conceptual terms. Interested objects in the images are represented by contours segmented from images. Image content such as shapes and spatial relationships are derived from object contours according to domain specific image knowledge. A three layered model is proposed for integrating image representations, extracted image features, and image semantics. With such a model, images can be retrieved based on the features and content specified in the queries. The knowledge based query processing is based on a query relaxation technique. The image features are classified by an automatic clustering algorithm and represented by Type Abstraction Hierarchies (TAHs) for knowledge based query processing. Since the features selected for TAH generation are based on context and user profile, and the TAHs can be generated automatically by a clustering algorithm from the feature database, our proposed image retrieval approach is scalable and context sensitive. The performance of the proposed knowledge based query processing is also discussed     

Θℜ-string: A geometry-based representation for efficientand effective retrieval of images by spatial similarity

A spatial similarity algorithm assesses the degree to which the spatial relationships among the domain objects in a database image conform to those specified in the query image. In this paper, we propose a geometry-based structure for representing the spatial relationships in the images and an associated spatial similarity algorithm. The proposed algorithm recognizes both translation, scale, and rotation variants of an image, and variants of the image generated by an arbitrary composition of translation, scale, and rotation transformations. The algorithm has Θ(n log n) time complexity in terms of the number of objects common to the database and query images. The retrieval effectiveness of the proposed algorithm is evaluated using the TESSA image collection     

Design of large intelligent image database systems

Image knowledge structure and an access method for retrieving images are two of the most important problems in the design of large intelligent image data base systems. In this article, we present a software architecture which utilizes an image knowledge structure, called 2D C⁺-string, as the theoretical basis for intelligent image data base systems. Our architecture also provides an efficient access method to quickly locate the desired images by pruning a large percentage of nonpromising iconic indices represented by 2D C⁺-strings. The 2D C⁺-string spatial knowledge representation makes the image data base system become more intelligent, while the access method supports effective image retrieval from a large image data base without degrading the system's overall performance. Experimental results show that our access method is flexible enough to adapt to the change of image data base and very efficient in reducing the number of searches in similarity retrieval. © 1996 John Wiley & Sons, Inc.     

An intelligent image database system

A prototype intelligent image database system (IIDS) that is based on a novel pictorial data structure is presented. This prototype system supports spatial reasoning, flexible image information retrieval, visualization, and traditional image database operations. A pictorial data structure, based on 2-D strings, provides an efficient means for iconic indexing in image database systems and spatial reasoning. The modular design of IIDS facilitates its implementation. Further extensions of the prototype system are discussed     

Approximating Content-Based Object-Level Image Retrieval

Object-level image retrieval is an active area of research. Given an image, a human observer does not see random dots of colors. Rather, he/she observes familiar objects in the image. Therefore, to make image retrieval more user-friendly and more effective and efficient, object-level image retrieval technique is necessary. Unfortunately, images today are mostly represented as 2D arrays of pixels values. The object-level semantics of the images are not captured. Researchers try to overcome this problem by attempting to deduce the object-level semantics through additional information such as the motion vectors in the case of video clips. Some success stories have been reported. However, deducing object-level semantics from still images is still a difficult problem. In this paper, we propose a color-spatial approach to approximate object-level image retrieval. The color and spatial information of the principle components of an object are estimated. The technique involves three steps: the selection of the principle component colors, the analysis of spatial information of the selected colors, and the retrieval process based on the color-spatial information. Two color histograms are used to aid in the process of color selection. After deriving the set of representative colors, spatial knowledge of the selected colors is obtained using a maximum entropy discretization with event covering method. A retrieval process is formulated to make use of the spatial knowledge for retrieving relevant images. A prototype image retrieval tool has been implemented on the Unix system. It is tested on two image database consisting of 260 images and 11,111 images respectively. The results show that the color-spatial approach is able to retrieve similar objects with much better precision than the sole color-based retrieval methods.     

Graph-based representation for similarity retrieval of symbolic images

Image retrieval from an image database by the image objects and their spatial relationships has emerged as an important research subject in these decades. To retrieve images similar to a given query image, retrieval methods must assess the similarity degree between a database image and the query image by the extracted features with acceptable efficiency and effectiveness. This paper proposes a graph-based model SRG (spatial relation graph) to represent the semantic information of the contained objects and their spatial relationships in an image with no file annotation. In an SRG graph, the image objects are symbolized by the predefined class names as vertices and the spatial relations between object pairs are represented as arcs. The proposed model assesses the similarity degree between two images by calculating the maximum common subgraph of two corresponding SRG’s through intersection, which has quadratic time complexity owing to the characteristics of SRG. Its efficiency remains quadratic regardless of the duplication rate of the object symbols. The extended model SRG_T is also proposed, with the same time complexity, for the applications that need to consider the topological relations among objects. A synthetic symbolic image database and an existing image dataset are used in the conducted experiments to verify the performance of the proposed models. The experimental results show that the proposed models have compatible retrieval quality with remarkable efficiency improvements compared with three well-known methods LCS_Clique, SIM_R, and 2D Be-string, where LCS_Clique utilizes the number of objects in the maximum common subimage as its similarity function, SIM_R uses accumulation-based similarity function of similar object pairs, and 2D Be-string calculates the similarity of 2D patterns by the linear combination of two 1D similarities.     

一种基于位平面综合特征的彩色图像检索方案

传统的基于颜色直方图的彩色图像检索方法存在严重不足.首先是丢失颜色空间分布信息及特征维数过高,更重要的是无法有效检索含噪声图像.为克服此缺陷,提出了一种基于位平面综合特征的彩色图像检索算法.首先,结合光照、锐化、模糊等噪声攻击特点,从原始彩色图像中提取出重要位平面;然后选取重要位平面的加权颜色直方图作为颜色特征,选取重要位平面的空间信息熵作为空间特征;再综合利用上述颜色、空间两个特征计算图像间内容的相似度,并进行彩色图像检索.仿真实验表明,算法能够准确和高效地查找出用户所需内容的彩色图像,并且具有较好的查准率和查全率(特别对于含噪声图像).     

一种基于彩色边缘综合特征的图像检索算法

图像特征的提取与表达是基于内容的图像检索技术基础。边缘是重要的视觉感知信息,也是图像最基本的特征之一,其在图像分析和理解中有重要价值。文中以视觉重要的图像边缘轮廓为基础,提出一种基于彩色边缘综合特征的图像检索算法。该算法首先利用Canny检测算子提取出原始图像的彩色边缘轮廓。然后构造出能全面反映边缘轮廓内容的3种直方图,即加权颜色直方图、角度直方图和梯度方向直方图。最后综合利用上述3种彩色边缘直方图计算图像间的内容相似度,并进行彩色图像检索。仿真实验表明,该算法能够准确和高效地查找出用户所需内容的彩色图像,并且具有较好的查准率和查全率。     

图像中物体空间关系的表示及在检索中的应用

基于图像中物体之间的空间关系的图像检索往往受困于待处理的图像中物体种类和空间位置难以自动准确地获取。文中基于物体识别算法的输出,提出一种对物体空间关系的三元组表示法,给出基于这种表示方法对图像索引、相似度计算和检索排序的方法及允许用户使用查询词和空间关系表达查询需求的二维输入界面,并实现原型系统。这种表示法具有良好的鲁棒性,可容忍物体识别算法一定程度的误差,将物体识别得到的置信度加入三元组表示法置信度计算和排序算法中,减少物体识别结果误差对检索性能的影响。在原型系统上的实验表明,该系统在实验中对包含物体位置关系的检索给出更准确的结果,在NDCG@m、MAP、F@m上均优于现有系统。     

基于颜色-空间特征的图像检索

虽然基于颜色直方图特征的图像检索方法简单、高效,但却丢失了颜色的空间分布信息.提出了一种基于颜色-空间特征的图像检索方法.该方法将图像内容看成由若干对象组成的集合,首先利用图像分割得到主要对象,然后根据对象的颜色、位置和形状特征计算图像间内容的相似度,再进行检索.实验结果表明,当图像中有明显的物体时,该方法与颜色直方图相比,能够更加准确和高效地查找出用户所需内容的图像,明显地提高了检索精度.     

Similar-shape retrieval in shape data management

Addresses the problem of similar-shape retrieval, where shapes or images in a shape database that satisfy specified shape-similarity constraints with respect to the query shape or image must be retrieved from the database. In its simplest form, the similar-shape retrieval problem can be stated as, “retrieve or select all shapes or images that are visually similar to the query shape or the query image's shape”. We focus on databases of 2D shapes-or equivalently, databases of images of flat or almost flat objects. (We use the terms “object” and “shape” interchangeably). Two common types of 2D objects are rigid objects, which have a single rigid component called a link, and articulated objects, which have two or more rigid components joined by movable (rotating or sliding) joints. An ideal similar-shape retrieval technique must be general enough to handle images of articulated as well as rigid objects. It must be flexible enough to handle simple query images, which have isolated shapes, and complex query images, which have partially visible, overlapping or touching objects. We discuss the central issues in similar-shape retrieval and explain how these issues are resolved in a shape retrieval scheme called FIBSSR (Feature Index-Based Similar-Shape Retrieval). This new similar-shape retrieval system effectively models real-world applications     

A new relevance feedback technique for iconic image retrieval based on spatial relationships

Due to the popularity of Internet and the growing demand of image access, the volume of image databases is exploding. Hence, we need a more efficient and effective image searching technology. Relevance feedback technique has been popularly used with content-based image retrieval (CBIR) to improve the precision performance, however, it has never been used with the retrieval systems based on spatial relationships. Hence, we propose a new relevance feedback framework to deal with spatial relationships represented by a specific data structure, called the 2D B_e-string. The notions of relevance estimation and query reformulation are embodied in our method to exploit the relevance knowledge. The irrelevance information is collected in an irrelevant set to rule out undesired pictures and to expedite the convergence speed of relevance feedback. Our system not only handles picture-based relevance feedback, but also deals with region-based feedback mechanism, such that the efficacy and effectiveness of our retrieval system are both satisfactory.