10 research outputs found

    Spectral Prediction of Juxtaposed Halftones Relying on the Two-by-two Dot Centering Model

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    In a color reproduction workflow, spectral prediction models are useful for establishing the correspondence between colorant sur- face coverages and resulting printed halftone color. Spectral predic- tion models enable calculation of the color gamut and establishment of the color separation tables. Discrete line juxtaposed halftoning, a recently proposed algorithm, is characterized by the fact that colorants formed by inks and ink superpositions are placed side by side. Juxtaposed halftoning is necessary when printing with special inks such as opaque or metallic inks. In order to predict the color of classical halftones, the Yule–Nielsen modified spectral Neugebauer model is generally used. However, this model may not predict the color of juxtaposed halftones, since the effective surface coverages of colorants and of possible colorant overlaps are unknown. In contrast, the two-by-two dot centering spectral prediction model developed by S. G. Wang enables the reflectance of slightly overlapping colorants to be captured and is therefore appropriate for predicting the color of juxtaposed halftones. Since this model requires a large calibration set, the authors use an estimation technique which predicts more than 90% of the two-by-two calibration pattern reflectances by measuring less than 10% of them. For juxtaposed halftoning, the two-by-two dot centering model offers high prediction accuracies and outperforms the different variants of the Yule–Nielsen spectral Neugebauer model for comparable setups

    Color Reproduction of Metallic-Ink Images

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    We study the color reproduction of full-color metallic-ink images. Full-color metallic-ink images are prints whose contributing colorants are exclusively made of colored metallic inks. Due to the presence of metallic particles, metallic inks show a metal-like luster. These particles are opaque and hide the underlying ink or substrate. In order to obtain predictable halftone colors, we need a juxtaposed halftoning method to create halftone dots of different colors side by side without overlapping. Juxtaposed halftoning invalidates many assumptions generally made for the color reproduction workflow. For printing metallic-ink images, one needs a color separation system creating surface coverages for the 8 metallic inks that correspond to the 8 Neugebauer primaries. For this purpose, we introduce a simple and fast method for N-color separation that relies either on Demichel’s or on a variant of Kueppers’ ink-to-colorant separations. Thanks to a unique set of ink-to-colorant formulas, pseudo-CMY ink values are separated into amounts of printable colorants. We also describe color separation procedures that are able to optimize different properties of the resulting metallic-ink images

    Yule-Nielsen based multi-angle reflectance prediction of metallic halftones

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    Spectral prediction models are widely used for characterizing classical, almost transparent ink halftones printed on a diffuse substrate. Metallic-ink prints however reflect a significant portion of light in the specular direction. Due to their opaque nature, multi-color metallic halftones require juxtaposed halftoning methods where halftone dots of different colors are laid out side-by-side. In this work, we study the application of the Yule-Nielsen spectral Neugebauer (YNSN) model on metallic halftones in order to predict their reflectances. The model is calibrated separately at each considered illumination and observation angle. For each measuring geometry, there is a different Yule-Nielsen n-value. For traditional prints on paper, the n-value expresses the amount of optical dot gain. In the case of the metallic prints, the optical dot gain is much smaller than in paper prints. With the fitted n-values, we try to better understand the interaction of light and metallic halftones

    N-Ink Printer Characterization with Barycentric Subdivision

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    Printing with a large number of inks, also called N-ink printing, is a challenging task. The challenges comprise spectral modelling of the printer, color separation, halftoning, and limitations of the amount of inks. Juxtaposed halftoning, a perfectly dot-off-dot halftoning method, has proven to be useful to address some of these challenges. However, for juxtaposed halftones, prediction of colors as a function of ink area-coverages has not yet been fully investigated. The goal of this paper is to introduce a spectral prediction model for N-ink juxtaposed-halftone prints. As the area-coverage domain of juxtaposed inks forms a simplex, we propose a cellular subdivision of the area-coverage domain using barycentric subdivision of simplexes. The barycentric subdivision provides algorithmically straightforward means to design and implement an N-ink color prediction model. Within the subdomain cells, the Yule-Nielsen spectral Neugebauer model is used for the spectral prediction. Our proposed model is highly accurate for prints with a large number of inks while requiring a relatively low number of calibration samples

    Robust density modelling using the student's t-distribution for human action recognition

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    The extraction of human features from videos is often inaccurate and prone to outliers. Such outliers can severely affect density modelling when the Gaussian distribution is used as the model since it is highly sensitive to outliers. The Gaussian distribution is also often used as base component of graphical models for recognising human actions in the videos (hidden Markov model and others) and the presence of outliers can significantly affect the recognition accuracy. In contrast, the Student's t-distribution is more robust to outliers and can be exploited to improve the recognition rate in the presence of abnormal data. In this paper, we present an HMM which uses mixtures of t-distributions as observation probabilities and show how experiments over two well-known datasets (Weizmann, MuHAVi) reported a remarkable improvement in classification accuracy. © 2011 IEEE

    Juxtaposed Color Halftoning Relying on Discrete Lines

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    Abstract—Most halftoning techniques allow screen dots to overlap. They rely on the assumption that the inks are transparent, i.e. the inks do not scatter a significant portion of the light back to the air. However, many special effect inks such as metallic inks, iridescent inks or pigmented inks are not transparent. In order to create halftone images, halftone dots formed by such inks should be juxtaposed, i.e. printed side by side. We propose an efficient juxtaposed color halftoning technique for placing any desired number of colorant layers side by side without overlapping. The method uses a monochrome library of screen elements made of discrete lines having rational thicknesses. Discrete line juxtaposed color halftoning is performed efficiently by multiple accesses to the screen element library. Index Terms—Color halftoning, discrete lines, juxtaposed halftoning, Neugebauer primaries, opaque inks I

    Acta Universitatis Sapientiae - Film and Media Studies 2016

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    Juxtaposed Color Halftoning Relying on Discrete Lines

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    A New Theory for Patent Subject Matter Eligibility: A Veblenian Perspective

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    Seventh Biennial Report : June 2003 - March 2005

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