This paper presents a novel method to recover planar projections (homographies) from perspectively distorted images of clustered-dot halftones. The method uses the variation of the local affine deformation of the halftone (estimated using a Fourier method) to recover the additional projective components. Evidence provided from simulated distortion and mobile capture shows that the approach provides an effective first step in the problem of using mobile device to recover stenographic information embedded in unknown halftone images, as pixel-accurate alignment is needed to recover the data.

At the microscopic level, printing on a substrate exhibits imperfections that can be used as a unique identifier for labels, documents and other printed items. In previous work, we have demonstrated using these minute imperfections around a simple forensic mark such as a single printed character for robust authentication of the character with a low cost (and mobile) system. This approach allows for product authentication even when there is only minimal printing (e.g. on a small label or medallion), supporting a variety of secure document workflows. In this paper, we present an investigation on the influence that the substrate type has on the imperfections of the printing process that are used to derive the character 'signature'. We also make a comparison between two printing processes, dry electro photographic process (laser) and (thermal) inkjet. Understanding the sensitivity of our methods to these factors is important so that we know the limitations of the approach for document forensics.

Forensic analysis of individual printed items, including single characters, provides a readily-integrated means to extend security to any printed item (label, document, package, etc.). In this paper we demonstrate, for the first time, forensic levels of image inspection for workflows involving two very different high-resolution imaging devices, the Dyson Relay CMOS Imaging Device (DrCID) and a high speed line-scan camera. In particular, we show how a similarity metric can be used to identify specific characters with less than 1 in 109chance of false matching, while closing the loop between in-line (production) using the line-scan camera and end-user (investigative) inspection with DrCID.

In the past few years we have witnessed the migration of cheap imaging devices into portable and mobile computing appliances such as PDAs and mobile phones. As these devices become ever more powerful in terms of processor speed and memory, new exciting applications and uses are being developed. A particularly useful one is the casual capture of text images for faxing, note taking, OCR, etcetera. This paper describes the image processing pipeline used to enhance images of text captured by a hand-held low-resolution camera, and a fast text extraction method. The main advantages of the approach are its inherent lightweight structure, speed and relative robustness under poor lighting and focus conditions. The computational efficiency (and a careful implementation) of the approach has allowed its deployment in an interactive-time text capture and foreign-text translation demo on a PDA with a VGA camera attachment.

This paper discusses advances made to the 3D geometrical model matching system within the TINA machine vision environment over the last 10 years including the recent inclusion of a verification stage. We show how this final step closes the loop on the object location system allowing the theoretical location performance to be attained, eliminating key assumptions used in the existing forward pass algorithms. We explain how the use of a system approach has been crucial to the development of key components and summarise our findings.

Abstract This paper presents a novel automatic method for view synthesis (or image transfer) from a triplet of uncalibrated images based on trinocular edge matching followed by transfer by interpolation, occlusion detection and correction and finally rendering. The edge-based technique proposed here is of general practical relevance because it does not rely upon dense correspondences and is computationally efficient. Applications range from immersive media and teleconferencing, image interpolation for fast rendering and compression.

Article View synthesis by edge transfer with application to the generation of immersive video objects Share on Authors: Stephen Pollard Hewlett-Packard Laboratories, Filton Road, StokeGifford, Bristol, BS34 8QZ, UK Hewlett-Packard Laboratories, Filton Road, StokeGifford, Bristol, BS34 8QZ, UKView Profile , Sean Hayes Hewlett-Packard Laboratories, Filton Road, StokeGifford, Bristol, BS34 8QZ, UK Hewlett-Packard Laboratories, Filton Road, StokeGifford, Bristol, BS34 8QZ, UKView Profile Authors Info & Claims VRST '98: Proceedings of the ACM symposium on Virtual reality software and technologyNovember 1998 Pages 91–98https://doi.org/10.1145/293701.293713Online:02 November 1998Publication History 7citation302DownloadsMetricsTotal Citations7Total Downloads302Last 12 Months1Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

This paper presents a novel automatic method for view synthesis (or image transfer) from a triplet of uncalibrated images based on trinocular edge matching followed by transfer by interpolation, occlusion detection and correction and finally rendering. The edge-based technique proposed here is of general practical relevance because it overcomes most of the problems encountered in other approaches that either rely upon dense correspondence, work in projective space or need explicit camera calibration. Applications range from immersive media and teleconferencing, image interpolation for fast rendering and compression.

Abstract We describe a working multi‐transputer stereo vision system which exploits various forms of parallelism in a number of visual competences upon a specialized hardware architecture that provides distributed video datapaths to the processor array. We exploit stereo and spatial parallelism to recover 3‐D scene descriptions from passive stereo vision. To recognize and recover the positions of modelled objects, we exploit featural parallelism at both the object and sub‐object level. We also describe a real‐time object‐tracking algorithm that exploits featural parallelism in the concurrent tracking of a set of object features. These competences have been integrated into a general‐purpose architecture and we present some performance results and descriptions of the use of this vision engine in two application domains.

In this paper a planar curve segmentation method based on the analysis of curvature and mean polygonal area is proposed. A rough segmentation of the curve is first produced by a high/low curvature classifier and then refined by a high/low/zero classifier and a knot/straight/convex/concave shape identifier so as to obtain a set of critical knots and shape descriptors for all segments. A straight line or conic approximation is then applied to each segment to generate a symbolic representation of the curve.

Abstract The topological obstacles to the matching of smooth curves in stereo images are shown to occur at epipolar tangencies. Matching is possible when these tangencies satisfy certain projective constraints (the tangent lines form corresponding pencils) and metric contraints dependent on the camera geometry. Such points are good matching primitives, even when the image curves correspond to smooth surface profiles. An iterative scheme for improving camera calibration based on these results is derived, and performance demonstrated on real data.