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L Xiao, H Heys, J A Robinson, "Visual Cryptography: Threshold Schemes and Information Hiding", Proceedings of the Newfoundland Electrical and Computer Engineering Conference 2000, NECEC'00, St. John's, Newfoundland, November 2000.
Visual threshold schemes are based on visual cryptography. Compared with common threshold schemes, visual threshold themes use an image as the information source of the secret. The secret is reconstructed by simply superimposing enough share images, and no computation is needed. Unless more than a certain number of share images are obtained, it is impossible to disclose the secret image. This feature enables visual threshold schemes to be used conveniently in highly confidential cases where the secret is shared by several members. Information hiding (steganography) is the art of masking the existence of the message. By concealing a secret image with several innocent-looking shares, information hiding can be achieved. This paper discusses visual cryptography in two main areas: threshold schemes and information hiding. The details of specific threshold schemes, their application in information hiding, and the relationship of visual cryptography and steganography are presented.

M A Shamim, J A Robinson, "Modified Binary Tree for Contour Coding and Its Performance Analysis", The Third Symposium on Wireless Personal Multimedia Communications, November 12-15, 2000, Bangkok, Thailand, pp 603-608.
The objective of this paper is to consider the coding of featured contours, i.e. texture, object or motion boundaries in images. The emerging MPEG-4 and MPEG-7 video coding standards look for a content based and multi-layered representation of video information. Therefore, efficient coding of object based information can play an important role in these latest standards. Here we propose a new coding scheme to efficiently code contour images. The coding algorithm uses an asymmetric binary tree scheme, which shows better performance than conventional quadtree, binary tree and READ coding algorithms applied on practical motion boundary images.

Q Song, J A Robinson, "A Feature Space for Face Image Processing", Proceedings of the International Conference on Pattern Recognition, Barcelona, September 2000, Volume 2, pp 97-100.
We propose criteria for a feature space for face image processing and a method for generating such a space. Beginning with many input dimensions, including deformation vectors (obtained through optical flow analysis between an input image and a neutral template) and deformation residues, we apply principal components analysis and Fisher's classification criterion to derive a feature space. We demonstrate classification in two important tasks -- face detection and expression analysis -- in each case using only one linear discriminant, thereby demonstrating that the feature space fulfils a restricted version of the criteria.

M A Shamim, J A Robinson, "Region-Based Motion Estimation in Image Sequences", Proceedings of the Canadian Conference on Electrical and Computering Engineering, CCECE'00, Halifax, Nova Scotia, Canada, May 2000, Volume 1, pp 317-321.
In this paper, we propose a method to segment moving objects in image sequences, so that each can be represented by its boundary and compact motion description. Assuming that a scene consists of a small number of moving objects, we process each pair of frames as follows: First we recursively identify a small number of "movement classes", each represented by two or more motion parameters. Second we use a spatially-segmented version of the reference frame (i.e. the later of the two frames) to classify segments into movement classes. Third we merge segments using various similarity heuristics. Experiment al results of some standard test sequences have shown that the proposed algorithm results in good quality motion segmentation with a small number of motion vectors.

C Robertson, J A Robinson, "Live Paper: Video Augmentation to Simulate Interactive Paper", Proceedings of ACM Multimedia 1999, Orlando, Florida, Oct 1999, part 2, pp 167-170.
We report progress in  the development of an augmented space to simulate paper with embedded computational facilities. We use a video camera and a data projector to turn sheets of paper into I/O devices. To the user, the illusion of paper as computer is strong. Our system provides audio and video augmentation, including collaboration with remote users through videowriting (real-time extraction of writing on a page) and projected annotations. 

A Vardy, J A Robinson, L-T Cheng, "The Wristcam as Input Device", Proceedings of the Third International Symposium on Wearable Computers, San Francisco, California, Oct 1999, pp 199-202.
We show how images of a users hand from a video camera attached to the underside of the wrist can be processed to yield finger movement information. Discrete (and discreet) movements of the fingers away from a rest position are translated into a small set of base symbols. These are interpreted as input to a wearable computer, providing unobtrusive control.

C Robertson, J A Robinson, Page Similarity and the Hausdorff Distance, Proceedings of the Seventh International Conference on Image Processing and its Applications, Manchester, UK, July 1999, pp 755-759.
The VideoWriter is a real-time system that uses digitzed images from a computer-controlled video camera to find the location of pages on a desktop. Once an image of a page is extracted, the system must determine if the page has been previously stored. In this paper, we investigate^ M the use of the Hausdorff distance metric to compare two-level versions of page images. The Hausdorff distance metric does not require exact corresponde nce between pels in images. We compare the accuracy of the original metric with several modifications.

C Y Ching, J Hiscock, X Cheng, J A Robinson, "Estimation of Gas Slug Velocities in Two-Phase Flows using Successive Images of the Flow", CANCAM'99, McMaster University, Ontario, Canada, May 30 - June 3, 1999.
The modeling of gas-liquid two-phase flows is important in a variety of applications. The complex nature of two-phase flows, characterized by turbulence, deformable phase interface, phase interaction, phase slip and compressibility of the gas phase, has made it extremely difficult to model. Despite its complexity, the distribution of gas and liquid in vertically-upward two-phase flows can be classified into a few dominant flow patterns or regimes: bubble flow, slug flow, churn flow and annular flow. The problem of two-phase flow modeling is greatly simplified by dealing only with these specific flow patterns, although an accurate estimation of the phase velocities remains critical for the success of the models. A method for estimating the absolute gas slug velocities in slug flow using successive images of the flow is presented in this paper.

L-T Cheng, J A Robinson, "Dealing with Speed and Robustness Issues for Video-Based Registration on a Wearable Computing Platform", Proceedings of the Second International Symposium on Wearable Computers, Pittsburgh, PA, Oct 19-20, 1998, pp 84-91.
We are investigating applications in which a field worker, equipped with a wearable computer, is networked wirelessly with a remote expert.  In this paper, we present a simple and fast augmented reality registration algorithm that can be used to lock annotations given by the remote expert onto parts of the scene viewed by the field worker through a head mounted see-through display.  The algorithm can also be used to construct an image mosaic interface for the remote expert to place annotation s regardless of the current viewpoint of the field worker.  We also present a desktop-based augmented reality prototype system to test the registration algorithm.  A manual recalibration user interface is being developed to deal with registration errors.

X Ping, J A Robinson, "Supervised object-based temporal filtering for enhancement of moving facial images", Proceedings of the Canadian Conference on Electrical and Computer Engineering, CCECE'98, Waterloo, Ontario, Canada, May 1998, Volume 1, pp 453-456.
We are interested in recovering accurate facial images from noisy and blurred videos based on 2D and 3D object modelling. Our strategy for enhancement is to employ warping to bring frames of video into correspondence before frame averaging. We use a 2D face model which consists of a set of landmarks that describe the main facial feature points. Experiments to test the strategy are included in the paper. Our results demonstrate that the supervised object-based temporal filtering strategy is simple and effective for enhancement of faces in videos.

J A Robinson, "In-Band Redundancy Removal for Binary Tree Predictive Coding", Proc First International Symposium on Communication Systems and Digital Signal Processing, Sheffield, UK, 6-8 April 1998, pp 52-55.
This paper reports two new methods for improving the performance of Binary Tree Predictive Coding (BTPC), a general-purpose still-image compression scheme. BTPC uses non-causal adaptive predictive coding to generate a set of prediction-error lattices of increasing density, plus side information to distinguish between ridge and valley points when these are identified by the predictor. The error lattices contain residual redundancy, particularly in areas of regular texture in the original image. The first new method removes the redundancy, by applying a further causal predictive coding stage yielding up to 4% additional compression. Adaptive coding of the ridge/valley side information provides a further 4%. These improvements are at their greatest in images with large regions of regular texture. It is therefore possible to improve the overall performance of BTPC by up to 8%, at the cost of increased encoding and decoding complexity.