Issue 1

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https://diglib.eg.org/handle/10.2312/94

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    An Advanced Color Representation for Lossy Compression of CMYK Prepress Images
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) De Neve, P.; Denecker, K.; Philips, W.; Lemahieu, I.
    CMYK color images are used extensively in prepress applications. When compressing those color images one has to deal with four different color channels. Usually compression algorithms only take into account the spatial redundancy that is present in the image data. This approach does not yield an optimal data reduction since there also exists a high correlation between the different colors in natural images.This paper shows that a significant gain in data reduction can be achieved by exploiting this color redundancy. Some popular transform coders, including DCT-based JPEG and the SPIHT wavelet coder, were used for reducing the spatial redundancy. The performance of the algorithms was evaluated using a quality criterion based on human perception like the mean CIEL*a*b*?E error.
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    Book Reviews
    (Blackwell Publishers Ltd and the Eurographics Association, 2000)
    Books reviewed:Salomon, David. Computer Graphics and Geometric ModelingGovil-Pai, Shalini and Pai, Rajesh. Learning Computer GraphicsRoelofs, Greg. PNG: The Definitive GuideMarsh, Duncan. Applied Geometry for Computer Graphics and CADMarchand, Patrick. Graphics and GUIs with MATLAB (2nd edition)Ammerall, Leen. Computer Graphics for Java Programmers
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    Editorial
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Coquillart, Sabine; Duke, David
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    Efficient Glossy Global Illumination with Interactive Viewing
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Stamminger, Marc; Scheel, Annette; Granier, Xavier; Perez-Cazorla, Frederic; Drettakis, George; Sillion, Francois
    The ability to perform interactive walkthroughs of global illumination solutions including glossy effects is a challenging open problem. In this paper we overcome certain limitations of previous approaches. We first introduce a novel, memory- and compute-efficient representation of incoming illumination, in the context of a hierarchical radiance clustering algorithm. We then represent outgoing radiance with an adaptive hierarchical basis, in a manner suitable for interactive display. Using appropriate refinement and display strategies, we achieve walkthroughs of glossy solutions at interactive rates for non-trivial scenes. In addition, our implementation has been developed to be portable and easily adaptable as an extension to existing, diffuse-only, hierarchical radiosity systems. We present results of the implementation of glossy global illumination in two independent global illumination systems.
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    Eurographics
    (Blackwell Publishers Ltd and the Eurographics Association, 2000)
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    Event Reports
    (Blackwell Publishers Ltd and the Eurographics Association, 2000)
    1999 Siggraph / Eurographics Workshop on Graphics HardwareGVE '99: 1999 Eurographics/ SIGGRAPH Workshop on Graphics and Visualization5th Eurographics Workshop on Multimedia
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    Geometrically-Aware Interactive Object Manipulation
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Choi, Min-Hyung; Cremer, James F.
    This paper describes formulation and management of constraints, and a nonlinear optimization algorithm that together enable interactive geometrically aware manipulation of articulated objects. Going beyond purely kinematic or dynamic approaches, our solution method directly employs geometric constraints to ensure non-interpenetration during object manipulation. We present the formulation of the inequality constraints used to ensure nonpenetration, describe how to manage the set of active inequality constraints as objects move, and show how these results are combined with a nonlinear optimization algorithm to achieve interactive geometrically aware object manipulation. Our optimization algorithm handles equality and inequality constraints and does not restrict object topology. It is an efficient iterative algorithm, quadratically convergent, with each iteration bounded by O(nnz(L)), where nnz(L) is the number of non-zeros in L, a Cholesky factor of a sparse matrix.
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    Observational Models of Graphite Pencil Materials
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Sousa, Mario Costa; Buchanan, John W.
    This paper presents models for graphite pencil, drawing paper, blenders, and kneaded eraser that produce realistic looking pencil marks, textures, and tones. Our models are based on an observation of how lead pencils interact with drawing paper, and on the absorptive and dispersive properties of blenders and erasers interacting with lead material deposited over drawing paper. The models consider parameters such as the particle composition of the lead, the texture of the paper, the position and shape of the pencil materials, and the pressure applied to them. We demonstrate the capabilities of our approach with a variety of images and compare them to digitized pencil drawings. We also present image-based rendering results implementing traditional graphite pencil tone rendering methods.
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    Texture-based Dither Matrices
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Veryovka, Oleg; Buchanan, John
    Continuous tone images must be halftoned to be displayed on binary output devices such as printers. Halftoning algorithms at low resolutions of the output hardware introduce textures into the resulting display. In this work we control halftoning texture by generating a threshold matrix from an image-based texture. We demonstrate that processing textures by the adaptive histogram equalization algorithm approximates pixel distribution properties of traditional dither screens. Ordered dithering with the resulting threshold matrix enables us to define texture in the halftoned image. We control the appearance of this texture by a combination of the ordered dither algorithm with an error diffusion process. We present applications of texture-based dither screens to both photorealistic and artistic rendering. In the case of photorealistic tone reproduction our technique preserves textures and edges of the original image. The ability to define an arbitrary texture enables us to introduce a variety of artistic effects, including embossing of images with textures and text, and approximation of the appearance of of conventional illustration media. We evaluate the resulting halftoning using multi-scale edge distortion measures. Our quantitative evaluation closely corresponds to the visual observations.