Computing world distances of scene features from the captured images is a common task in image analysis and scene understanding. Projective geometry based methods focus on measuring distance from one single image, the scope of measurable scene is limited by the field-of-view (FOV) of one single camera. With a full view panorama, the scope of measurable scene is no longer limited by FOV. However, the scope of measurable scene is limited by the fixed capture location of a single panorama. In this paper, we propose one method of measuring distances of line segments in real world scene using panoramic video representation. The scope of measurable scene is largely extended without the limitation of FOV and a fixed capture location. A prototype system called PVMeasure is developed to allow user to interactively measure the distances of line segments in a panoramic video. Experiment results verify that the method offers good accuracy.

Multi-channel display system is more suitable for collaboration applications than common desktop PC. In tradition, such multi-channel displays are used by a group of collocated users. In this paper, we propose one remote interaction system to allow a group of users to simultaneously access the multi-channel display on common PCs. Our system can achieve real time performance under mainstream network environment, which is difficult for the previous work even under the network testbed of high bandwidth. In the system, the multi-channel video generated on the server side is captured by synchronizing a group of capturing processes. For achieving real time performance, one hierarchical subtile-based approach is designed to represent and compress the multi-channel video using MPEG2. The system selectively streams the bitstream containing the region of visible pixels to the corresponding client. For controlling the multichannel application on client side, we refactor the architecture of VNC software, and integrate the enhanced version into our system. Experimental results show that our system achieves real time performance when simultaneously serving group users.

This paper presents an approach of replacing textures of specified regions in the input image and video using stretch-based mesh optimization.. The retexturing results have the similar distortion and shading effects conforming to the underlying geometry and lighting conditions. For replacing textures in single image,two important steps are developed: the stretch-based mesh parametrization incorporating the recovered normal information is deduced to imitate perspective distortion of the region of interest; the Poisson-based refinement process is exploited to account for texture distortion at fine scale. The luminance of the input image is preserved through color transfer in YCbCr color space. Our approach is independent of the replaced textures. Once the input image is processed, any new texture can be applied to efficiently generate the retexturing results. For video retexturing, we propose key-frame-based texture replacement extended and generalized from the image retexturing. Our approach repeatedly propagates the replacement result of key frame to the rest of the frames. We develop the local motion optimization scheme to deal with the inaccuracies and errors of robust optical flow when tracking moving objects. Visibility shifting and texture drifting are effectively alleviated using graphcut segmentation algorithm and the global optimization to smooth trajectories of the tracked points over temporal domain. Our experimental results showed that the proposed approach can generate visually pleasing results for both image and video.

Computing distance from captured images is a common task in image analysis and scene understanding. Distance serves as building block for calculating other geometry information, such as area and volume. Besides directly measuring distance on the spot, it can be computed using projective geometry from scene images. Existing work on distance measurement consider point or line constraints. Since circles are common in daily life, we propose two methods of measuring distance using circles in one captured image. The first method deals with two separate circles, which can be coplanar or in parallel planes. The second one handles two concentric circles on the same plane, which offers higher accuracy than directly solving equations of concentric circles. Both methods are verified by experiments with simulated data and real images.

Computing world distances of scene features from the captured images is a common task in image analysis and scene understanding. Previous projective geometry based methods focus on measuring distance from one single image. Hence, the scope of measurable scene is limited by the field-of-view (FOV) of one single camera. In this paper, we propose one method of measuring distances of line segments in real world scene using panorama representation. With a full view panorama, the scope of measurable scene is increased and can fully cover the sphere of 360 times 360 FOV. With panorama representation, distance of long-range features, which can not be fully captured by a single image, can be measured from the panoramic image. A prototype system called PanoMeasure is developed for enabling user to interactively measure the distances of line segments. Experiments with simulated data and real measurement results verify that the method offers high accuracy.

With the rapid advances of digital photography technology, high resolution video can be recorded using video camera for home entertainment and digital cinema. High end projector used for high resolution video display is bulky and expensive, only suitable for fixed installation, and prevents itself from being widely adopted. In this paper, we present one high resolution video display system using multiple projectors to replace the high end projector playback system. Our system is driven by single PC with PCI-E16 x interface and supports at least triple projectors, which is suitable for building surround video display system. It fully exploits the high bandwidth between CPU and graphics card, and efficiently plays back high resolution video of any format supported by commercial video player. We design geometric alignment and photometric correction methods to display the video content seamlessly on the planar display screen. Experimental results show that our system displays high resolution video at its full frame rate.

Abstract We present a data‐driven approach that synthesizes tree animations from a set of pre‐computed motion data. Our approach improves previous motion synthesis algorithms for character animation in several aspects. We first introduce a simple yet effective sampling scheme to generate a rich and reusable motion database for each tree model. We also propose a novel technique to generate a fine set of transitions that are uniformly distributed in the motion database. The transition lengths are adaptively determined according to the similarity of the transiting frame pairs. In the runtime, we employ a greedy searching algorithm to synthesize smooth tree animations under an adjustable wind condition. Experimental results show that our approach achieves comparable quality to physically based methods, while in orders of magnitude faster performance. Copyright © 2007 John Wiley & Sons, Ltd.

With the explosion of the mobile communication market, more and more handheld devices act as clients in the Internet. People use these devices to purchase books, play games, receive emails, etc. For protecting privacies, such applications should integrate digital signature schemes. Since handheld devices have poor computational capabilities and limited battery life, traditional computation intensive digital signature protocols that are based on asymmetric cryptographic algorithms are not suitable for mobile devices. We propose a server based signature (SBS) scheme for mobile devices. Besides achieving the same security level of the traditional digital signature protocols, the SBS scheme also: 1) reduces the computation complexity on the mobile devices; 2) reduces the communication consumption between signer and verifier. Application results show that our scheme is very useful for mobile communication systems.

This paper introduces a practical approach for superresolution, the process of reconstructing a high-resolution image from the low-resolution input ones. The emphasis of our work is to super-resolve frames from dynamic video sequences, which may contain significant object occlusion or scene changes. As the quality of super-resolved images highly relies on the correctness of image alignment between consecutive frames, we employ the robust optical flow method to accurately estimate motion between the image pair. An efficient and reliable scheme is designed to detect and discard incorrect matchings, which may degrade the output quality. We also introduce the usage of elliptical weighted average (EWA) filter to model the spatially variant point spread function (PSF) of acquisition system in order to improve accuracy of the model. A number of complex and dynamic video sequences are tested to demonstrate the applicability and reliability of our algorithm.

The representation of moving geometry entities is an important issue in the fields of CAD/CAM and robotic motion design. We present a method to interpolate the moving frame homogeneously using B-splines. By analysing the matrix representation of the moving frames, a simplified optimization functional is derived and a recursive iteration method is presented for approximating orthogonal frames at any position. The error caused by approximation and interpolation is given and is shown to be controllable. Since the calculation of moving frames is only related to linear equations of two or three unknowns, and the moving frames are approximated with a low-degree polynomial B-spline, the proposed approach can run very fast. The method is useful in motion design and the swept volume representation.