Abstract

Traditional visual servoing is able to navigate a robotic system between two views of the same object. However, it is not designed to servo between views of different objects. In this paper, we consider a novel problem of servoing any instance (exemplar) of an object category to a desired pose (view) and propose a strategy to accomplish the task. We use features that semantically encode the locations of object parts and define the servoing error as the difference between positions of corresponding parts in the image space. Our controller is based on the linear combination of 3D models, such that the resulting model interpolates between the given and desired instances. We conducted our experiments on five different object categories in simulation framework and show that our approach achieves the desired pose with smooth trajectory. Furthermore, we show the performance gain achieved by using a linear …

Abstract

In this work, we propose an online handwriting solution, where the data is captured with the help of depth sensors. Users may write in the air and our method recognizes it in real time using the proposed feature representation. Our method uses an efficient fingertip tracking approach and reduces the necessity of pen-up/pen-down switching. We validate our method on two depth sensors, Kinect and Leap Motion Controller. On a dataset collected from 20 users, we achieve a recognition accuracy of 97.59% for character recognition. We also demonstrate how this system can be extended for lexicon recognition with reliable performance. We have also prepared a dataset containing 1,560 characters and 400 words with the intention of providing common benchmark for handwritten character recognition using depth sensors and related research.

Abstract

Most of the popular optical character recognition (OCR) architectures use a set of handcrafted features and a powerful classifier for isolated character classification. Success of these methods often depend on the suitability of these features for the language of interest. In recent years, whole word recognition based on Recurrent Neural Networks (RNN) has gained popularity. These methods use simple features such as raw pixel values or profiles. Success of these methods depend on the learning capabilities of these networks to encode the script and language information. In this work, we investigate the possibility of learning an appropriate set of features for designing OCR for a specific language. We learn the language specific features from the data with no supervision. This enables the seamless adaptation of the architecture across languages. In this work, we learn features using a stacked Restricted Boltzman …

Abstract

Dynamic time warping (DTW) is a popular distance measure used for recognition free document image retrieval. However, it has quadratic complexity and hence is computationally expensive for large scale word image retrieval. In this paper, we use a fast approximation to the DTW distance, which makes word retrieval efficient. For a pair of sequences, to compute their DTW distance, we need to find the optimal alignment from all the possible alignments. This is a computationally expensive operation. In this work, we learn a small set of global principal alignments from the training data and avoid the computation of alignments for query images. Thus, our proposed approximation is significantly faster compared to DTW distance, and gives 40 times speed up. We approximate the DTW distance as a sum of multiple weighted Eulidean distances which are known to be amenable to indexing and efficient retrieval. We …

Abstract

In this work, we investigate the utility of Recurrent Neural Networks (RNNs) for script and language identification. Both these problems have been attempted in the past with representations computed from the distribution of connected components or characters (e.g. texture, n-gram). Often these features are computed from a larger segment (a paragraph or a page). We argue that one can predict the script or language with minimal evidence (e.g. given only a word or a line) very accurately with the help of a pre-trained RNN. We propose a simple and generic solution for the task of script and language identification which do not require any special tuning. Our method represents the word images as a sequence of feature vectors, and employ the RNNs for the identification. We verify the method on a large corpus of more than 15.03M words from 55K document images comprising 15 scripts and languages. We report an …

Abstract

Relative attributes help in comparing two images based on their visual properties. These are of great interest as they have been shown to be useful in several vision related problems such as recognition, retrieval, and understanding image collections in general. In the recent past, quite a few techniques have been proposed for the relative attribute learning task that give reasonable performance. However, these have focused either on the algorithmic aspect or the representational aspect. In this work, we revisit these approaches and integrate their broader ideas to develop simple baselines. These not only take care of the algorithmic aspects, but also take a step towards analyzing a simple yet domain independent patch-based representation for this task. This representation can capture local shape in an image, as well as spatially rigid correspondences across regions in an image pair. The baselines are extensively evaluated on three challenging relative attribute datasets (OSR, LFW-10 and UT-Zap50K). Experiments demonstrate that they achieve promising results on the OSR and LFW-10 datasets, and perform better than the current state-of-the-art on the UT-Zap50K dataset. Moreover, they also provide some interesting insights about the problem, that could be helpful in developing the future techniques in this domain.

Abstract

The problem of labeling the edges present in a single color image as convex, concave, and occluding entities is one of the fundamental problems in computer vision. It has been shown that this information can contribute to segmentation, reconstruction and recognition problems. Recently, it has been shown that this classification is not straightforward even using RGBD data. This makes us wonder whether this apparent simple cue has more information than a depth map? In this paper, we propose a novel algorithm using random forest for classifying edges into convex, concave and occluding entities. We release a data set with more than 500 RGBD images with pixel-wise ground labels. Our method produces promising results and achieves an F-score of 0.84 on the data set.

Abstract

Typical retrieval systems have three requirements: a) Accurate retrieval ie, the method should have high precision, b) Diverse retrieval, ie, the obtained set of points should be diverse, c) Retrieval time should be small. However, most of the existing methods address only one or two of the above mentioned requirements. In this work, we present a method based on randomized locality sensitive hashing which tries to address all of the above requirements simultaneously. While earlier hashing approaches considered approximate retrieval to be acceptable only for the sake of efficiency, we argue that one can further exploit approximate retrieval to provide impressive trade-offs between accuracy and diversity. We extend our method to the problem of multi-label prediction, where the goal is to output a diverse and accurate set of labels for a given document in real-time. Moreover, we introduce a new notion to simultaneously evaluate a method's performance for both the precision and diversity measures. Finally, we present empirical results on several different retrieval tasks and show that our method retrieves diverse and accurate images/labels while ensuring -speed-up over the existing diverse retrieval approaches.

Abstract

We address the problem of image retrieval using textual queries. In particular, we focus on descriptive queries that can be either in the form of simple captions (eg,``a brown cat sleeping on a sofa''), or even long descriptions with multiple sentences. We present a probabilistic approach that seamlessly integrates visual and textual information for the task. It relies on linguistically and syntactically motivated mid-level textual patterns (or phrases) that are automatically extracted from available descriptions. At the time of retrieval, the given query is decomposed into such phrases, and images are ranked based on their joint relevance with these phrases. Experiments on two popular datasets (UIUC Pascal Sentence and IAPR-TC12 benchmark) demonstrate that our approach effectively retrieves semantically meaningful images, and outperforms baseline methods.

Abstract

The recognition of human activities is one of the key problems in video understanding. Action recognition is challenging even for specific categories of videos, such as sports, that contain only a small set of actions. Interestingly, sports videos are accompanied by detailed commentaries available online, which could be used to perform action annotation in a weakly-supervised setting. For the specific case of Cricket videos, we address the challenge of temporal segmentation and annotation of actions with semantic descriptions. Our solution consists of two stages. In the first stage, the video is segmented into "scenes", by utilizing the scene category information extracted from text-commentary. The second stage consists of classifying videoshots as well as the phrases in the textual description into various categories. The relevant phrases are then suitably mapped to the video-shots. The novel aspect of this work is the …