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Item A Vector-based Representation for Image Warping(Blackwell Publishers Ltd and the Eurographics Association, 2000) Froumentin, Max; Labrosse, Frederic; Willis, PhilipA method for image analysis, representation and re-synthesis is introduced. Unlike other schemes it is not pixel based but rather represents a picture as vector data, from which an altered version of the original image can be rendered. Representing an image as vector data allows performing operations such as zooming, retouching or colourising, avoiding common problems associated with pixel image manipulation. This paper brings together methods from the areas of computer vision, image compositing and image based rendering to prove that this type of image representation is a step towards accurate and efficient image manipulation.Item Rendering NURB Regions For 2D Animation(Blackwell Science Ltd and the Eurographics Association, 1992) Willis, Philip; Oddy, RobertWe describe an accurate method of rendering by scan-conversion of closed regions bounded by NURBs, with particular comments on its application to computer-based 2D animation. It is shown that the method is fast, analytically accurate, and can be readily extended to include anti-aliasing and clipping.Item Scan Converting Extruded Lines at Ultra High Definition(Blackwell Publishing Ltd and the Eurographics Association, 1987) Willis, Philip; Watters, GeoffWe consider the problem of generating freehand raster graphics pictures at ultra high definition (typically one gigapixel per picture) by scan converting extruded lines. We describe a fast scan conversion algorithm which is linear in final resolution and which incorporates a number of features to ensure high efficiency. Sample pictures and corresponding performance figures are included.Item Projective Alpha Colour(The Eurographics Association and Blackwell Publishing, Inc, 2006) Willis, PhilipAlpha colours were introduced for image compositing, using a pixel coverage model. Algebraically they resemble homogeneous coordinates, widely used in projective geometry calculations. We show why this is the case. This allows us to extend alpha beyond compositing, to all colour calculations regardless of whether pixels are involved and without the need for a coverage model. Our approach includes multi-channel spectral calculations and removes the need for 7 channel and 6 channel alpha colour operations. It provides a unified explanation of pre-multiplied and non pre-multiplied colours, including negative coordinates and infinite points in colour space. It permits filter and illumination operations. It unifies the three existing significant compositing models in a single framework. It achieves this with a physically-plausible energy basis.Keywords: projective geometry, homogeneous coordinates, image compositing, alpha blending, alpha compositing, colour representation, filtering, spectral colour, projective alpha colourItem ARTcams: Attributed Rational Tensor Cameras(The Eurographics Association, 2009) Li, Chuan; Hall, Peter; Willis, Philip; Oliver Deussen and Peter HallNon-linear camera models are playing an increasingly important role in computer graphics, especially in image based rendering and non-photorealistic rendering. We introduce ARTcams as simple non-linear cameras, which are unique in combining both geometric projection and non-geometric attributes such as colour into a single model. The geometric component of an ARTcam subsumes many contemporary non-linear cameras, including General Linear Cameras, push-broom cameras, and X-slit cameras. The colour component generalises compositing operations. ARTcams, though, by combining geometry and other attributes generalise yet further. ARTcams can be thought of as lenses (or mirrors) that can reproduce a wide variety of real effects, including aerial perspective, depth of field, as well as both geometric and chromatic aberrations. They can be calibrated for both geometry and colour against real optical devices. It is possible to specify ARTcams by drawing alone. This paper explains and demonstrates the ARTcam model.Item UltraPaint: A New Approach to a Painting System(Blackwell Publishing Ltd and the Eurographics Association, 1987) Watters, Geoff; Willis, PhilipThe ideas underlying a Painting System being developed at the University of Bath are introduced. This differs from a conventional system in that ultra high definition pictures of upto 1 gigabyte may be created. We discuss approaches to implementing a number of standard paint program utilities in a form suited to our high definition method. Finally, we describe an algorithm for the rapid extrusion of brush strokes on a raster device.Item Graphical Interaction Management(Blackwell Publishing Ltd and the Eurographics Association, 1987) Barn, Balbir S.; Willis, PhilipGraphical interfaces and interactive graphical programmes are awkward to write because of a lack of top-down structure. A methodology for constructing graphical programs will be described, together with a system that generates the basic interaction requirements for such applications.Item Browsing High Definition Colour Pictures(Blackwell Publishing Ltd and the Eurographics Association, 1985) Willis, Philip; Milford, DavidThe authors describe a method of presenting colour pictures which allows users to browse by panning and zooming. The pictures are seen as though on a 512 by 512 by 12 bit framestore, but are defined to 4096 by 4096. The implementation allows the entire picture to be seen in overview, with fine details averaged, or to be zoomed in upon with finer detail progressively revealed by a sequence of twofold linear magnifications. Further zooming, beyond the resolution of the picture data, automatically produces a conventional pixel replication effect. In addition, the picture may be panned vertically or horizontally.Item Classification of Quad-encoding Techniques(Blackwell Science Ltd and the Eurographics Association, 1991) Hunter, Andrew; Willis, PhilipMany quad encoding technique have been published previously, using a variety of approaches to the different facets of quad storage, representation and manipulation. We review the major classes and identify three parameters which distinguish them. These are then used explicitly to classify a large number of published methods, with short discussion on each. In doing this we are also able to highlight some new approaches, to identify rare examples which escape the classification, and to suggest approaches to choosing a method to suit a given application.Item Image Interpolation by Pixel-Level Data-Dependent Triangulation(The Eurographics Association and Blackwell Publishing Ltd., 2004) Su, Dan; Willis, PhilipWe present a novel image interpolation algorithm. The algorithm can be used in arbitrary resolution enhancement, arbitrary rotation and other applications of still images in continuous space. High-resolution images are interpolated from the pixel-level data-dependent triangulation of lower-resolution images. It is simpler than other methods and is adaptable to a variety of image manipulations. Experimental results show that the new 'mesh image' algorithm is as fast as the bilinear interpolation method. We assess the interpolated images' quality visually and also by the MSE measure which shows our method generates results comparable in quality to slower established methods. We also implement our method in graphics card hardware using OpenGL which leads to real-time high-quality image reconstruction. These features give it the potential to be used in gaming and image-processing applications.