Abstract

The automatic discovery of distinctive parts for an ob-ject or scene class is challenging since it requires simulta-neously to learn the part appearance and also to identify the part occurrences in images. In this paper, we propose a simple, efficient, and effective method to do so. We ad-dress this problem by learning parts incrementally, starting from a single part occurrence with an Exemplar SVM. In this manner, additional part instances are discovered and aligned reliably before being considered as training exam-ples. We also propose entropy-rank curves as a means of evaluating the distinctiveness of parts shareable between categories and use them to select useful parts out of a set of candidates.We apply the new representation to the task of scene cat-egorisation on the MIT Scene 67 benchmark. We show that our method can learn parts which are significantly more in-formative and for a fraction of the cost, compared to previ-ous part-learning methods such as Singhet al. [28]. We also show that a well constructed bag of words or Fisher vector model can substantially outperform the previous state-of-the-art classification performance on this data.

Abstract

We aim to decompose a global histogram representation of an image into histograms of its associated objects and re-gions. This task is formulated as an optimization problem,given a set of linear classifiers, which can effectively dis-criminate the object categories present in the image. Our decomposition bypasses harder problems associated with accurately localizing and segmenting objects. We evaluate our method on a wide variety of composite histograms, and also compare it with MRF-based solutions. In addition to merely mea suring the accuracy of decomposition, we also show the utility of the estimated object and background his-tograms for the task of image classification on thePASCALVOC2007dataset.

Abstract

We present an approach for the text-to-image retrieval problem based on textual content present in images. Given the recent developments in understanding text in images, an appealing approach to address this problem is to localize and recognize the text, and then query the database, as in a text retrieval problem. We show that such an approach, de-spite being based on state-of-the-art methods, is insufficient,and propose a method, where we do not rely on an exact lo-calization and recognition pipeline. We take a query-driven search approach, where we find approximate locations of characters in the text query, and then impose spatial con-straints to generate a ranked list of images in the database.The retrieval performance is evaluated on public scene text datasets as well as three large datasets, namely IIIT scene text retrieval, Sports-10K and TV series-1M, we introduce.

Abstract

Existing mobile image instance retrieval applications as-sume a network-based usage where image features are sent to a server to query an online visual database. In this scenario, there are no restrictions on the size of the vi-sual database. This paper, however, examines how to per-form this same task offline, where the entire visual index must reside on the mobile device itself within a small mem-ory footprint. Such solutions have applications on location recognition and product recognition. Mobile instance re-trieval requires a significant reduction in the visual index size. To achieve this, we describe a set of strategies that can reduce the visual index up to 60-80×compared to a standard instance retrieval implementation found on desk-tops or servers. While our proposed reduction steps affect the overall mean Average Precision (mAP), they are ableto maintain a good Precision for the top Kresults (PK).We argue that for such offline application, maintaining agood PKis sufficient. The effectiveness of this approach is demonstrated on several standard databases. A working application designed for a remote historical site is also pre-sented. This application is able to reduce an 50,000 image index structure to 25 MBs while providing a precision of97%forP10and 100%forP1

Abstract

n this paper, we present a solution towards building a retrieval system over handwritten document images that i) is recognition-free, ii) allows text-querying, iii) can retrieve at sub-word level, iv) can search for out-of-vocabulary words. Unlike previous approaches that operate at either character or word lev-els, we use character n-gram images (CNG-img) as the retrieval primitive.CNG-img are sequences of character segments, that are represented and matched in the image-space. The word-images are now treated as a bag-of-CNG-img, that can be indexed and matched in the feature space. This allows for recognition-free search (query-by-example), which can retrieve morphologically similar words that have matching sub-words. Further, to enable query-by-keyword, we build an automated scheme to generate labeled exemplars for characters and character n-grams, fromun constrained handwritten documents. We pose this problem as one of weakly-supervised learning, where character/n-gram labeling is obtained automatically from the word labels. There sulting retrieval system can answer queries from an unlimited vocabulary. The approach is demonstrated on the George Wash-ington collection, results show major improvement in retrieval performance as compared to word-recognition and word-spotting methods

Abstract

Optical Character Recognition (OCR) problems areoften formulated as isolated character (symbol) classification task followed by a post-classification stage (which contains modules like Unicode generation, error correction etc. ) to generate the textual representation, for most of the Indian scripts. Such approaches are prone to failures due to (i) difficulties in designing reliable word-to-symbol segmentation module that can robustly work in presence of degraded (cut/fused) images and (ii) convert-ing the outputs of the classifiers to a valid sequence of Unicodes.In this paper, we propose a formulation, where the expectations on these two modules is minimized, and the harder recognition task is modelled as learning of an appropriate sequence to sequence translation scheme. We thus formulate the recognition as a direct transcription problem. Given many examples of feature sequences and their corresponding Unicode representations, our objective is to learn a mapping which can convert a word directly in to a Unicode sequence. This formulation has multiple practical advantages: (i) This reduces the number of classes significantly for the Indian scripts. (ii) It removes the need for a reliable word-to-symbol segmentation. (ii) It does not require strong annotation of symbols to design the classifiers, and (iii) It directly generates a valid sequence of Unicodes. We test our method on more than 6000 pages of printed Devanagari documents from multiple sources. Our method consistently outperforms other state of the art implementations.

Abstract

Recognizing text in images taken in the wild is achallenging problem that has received great attention in recentyears. Previous methods addressed this problem by first detectingindividual characters, and then forming them into words. Suchapproaches often suffer from weak character detections, due tolarge intra-class variations, even more so than characters fromscanned documents. We take a different view of the problemand present a holistic word recognition framework. In this,we first represent the scene text image and synthetic imagesgenerated from lexicon words using gradient-based features. Wethen recognize the text in the image by matching the scene andsynthetic image features with our novel weighted Dynamic TimeWarping (wDTW) approach.We perform experimental analysis on challenging publicdatasets, such as Street View Text and ICDAR 2003. Ourproposed method significantly outperforms our earlier work inMishraet al.(CVPR 2012), as well as many other recent works,such as Novikovaet al.(ECCV 2012), Wanget al.(ICPR 2012),Wanget al.(ICCV 2011)

Abstract

Understanding positional semantics of the environment plays an important role in manipulating an object in clutter. The interaction with surrounding objects in the environment must be considered in order to perform the task without causing the objects fall or get damaged. In this paper, we learn the semantics in terms of support relationship among different objects in a cluttered environment by utilizing various photometric and geometric properties of the scene. To manipulate an object of interest, we use the inferred support relationship to derive a sequence in which its surrounding objects should be removed while causing minimal damage to the environment. We believe, this work can push the boundary of robotic applications in grasping, object manipulation and picking-from-bin, towards objects of generic shape and size and scenarios with physical contact and overlap. We have created an RGBD dataset that consists of various objects used in day-to-day life present in clutter. We explore many different settings involving different kind of object-object interaction. We successfully learn support relationships and predict support order in these settings.

Abstract

Detecting compact overlapping communities in large networks is an important pattern recognition proble mwith applications in many domains. Most community de-tection algorithms trade-off between community sizes, their compactness and the scalability of finding communities. Clique Percolation Method (CPM) [1] and Local Fitness Maximization(LFM) [2] are two prominent and commonly used overlapping community detection methods that scale with large networks.However, significant number of communities found by the mare large, noisy, and loose. In this paper, we propose a general algorithm that takes such large and loose communities generated by any method and refines them into compact com-munities in a systematic fashion. We define a new measure of community-ness based on eigenvector centrality, identify loose communities using this measure and propose an algorithm for partitioning such loose communities into compact communities.We refine the communities found by CPM and LFM using our method and show their effectiveness compared to the original communities in a recommendation engine task.

Abstract

Labels associated with social images are valuable source of information for tasks of image annotation, understanding and retrieval.These labels are often found to be noisy, mainly due to the collabo-rative tagging activities of users. Existing methods on annotation havebeen developed and verified on noise free labels of images. In this paper,we propose a novel and generic framework that exploits the collective knowledge embedded in noisy label co-occurrence pairs to derive robust annotations. We compare our method with a well-known image annota-tion algorithm and show its superiority in terms of annotation accuracy on benchmark Corel5K and ESP datasets in presence of noisy labels.