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Now showing 1 - 5 of 5
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    A Vector-based Representation for Image Warping
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Froumentin, Max; Labrosse, Frederic; Willis, Philip
    A 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.
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    Projective Alpha Colour
    (The Eurographics Association and Blackwell Publishing, Inc, 2006) Willis, Philip
    Alpha 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 colour
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    ARTcams: Attributed Rational Tensor Cameras
    (The Eurographics Association, 2009) Li, Chuan; Hall, Peter; Willis, Philip; Oliver Deussen and Peter Hall
    Non-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.
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    Image Interpolation by Pixel-Level Data-Dependent Triangulation
    (The Eurographics Association and Blackwell Publishing Ltd., 2004) Su, Dan; Willis, Philip
    We 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.
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    A Modular Physical-Simulation Methodology
    (The Eurographics Association, 2010) Schanda, Florian; Willis, Philip; Kenny Erleben and Jan Bender and Matthias Teschner
    Physical simulation is useful so that the behaviour of objects emerges from the actions performed on them. However, a simulation simulates only one thing: the mechanics of collision behaviour for example. Further physical properties require further simulators and the problems of making them work effectively together escalate. We offer a structured way of making multiple simulations cooperate. The methodology is reviewed, then demonstrated in use with examples of how users might construct novel objects, such as an electric motor, whose properties emerge from the combined effects of the simulations on its components. The approach has potentially wide uses, for example in interactive games, in a virtual teaching laboratory or in interactive virtual museum exhibits. Users can create new objects which behave in predictable ways, discover solutions other than those built in by a game designer or extend a virtual experiment in exploratory ways. For the designer of the game or experiment, our approach requires fewer scripts and gives more play value for the design effort.