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Top 20 Most Read Articles
April 2012
The 20 articles with the most full-text downloads during the month, in descending order.
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Visual Discomfort and Visual Fatigue of Stereoscopic Displays: A Review J. Imaging Sci. Technol. Vol. 53, 030201 (Apr 23 2009) Online Publication Date: 23 April 2009
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Visual discomfort has been the subject of considerable research in relation to stereoscopic and autostereoscopic displays. In this paper, the importance of various causes and aspects of visual discomfort is clarified. When disparity values do not surpass a limit of 1°, which still provides sufficient range to allow satisfactory depth perception in stereoscopic television, classical determinants such as excessive binocular parallax and accommodation-vergence conflict appear to be of minor importance. Visual discomfort, however, may still occur within this limit and we believe the following factors to be the most pertinent in contributing to this: (1) temporally changing demand of accommodation-vergence linkage, e.g., by fast motion in depth; (2) three-dimensional artifacts resulting from insufficient depth information in the incoming data signal yielding spatial and temporal inconsistencies; and (3) unnatural blur. In order to adequately characterize and understand visual discomfort, multiple types of measurements, both objective and subjective, are required. |
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Beyond Red–Green–Blue (RGB): Spectrum-Based Color Imaging Technology J. Imaging Sci. Technol. Vol. 52, 010201 (Jan 15 2008) Online Publication Date: 15 January 2008
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This article presents a comprehensive study on the spectrum-based color reproduction system, called Natural Vision (NV), which aims to break through the limitation of red–green–blue (RGB) three-primary schemes. After a basic discussion on the motivation for color imaging technology beyond RGB, the method for systematizing the multispectral and multiprimary color imaging technologies, including image capture, processing, storage, printing, and display, is presented. Then experimental multispectral systems for both still image and video are introduced, and the following features of spectrum-based scheme are revealed: a) highly accurate color reproduction is possible even under different illumination environment, b) an expanded color gamut can be reproduced by multiprimary color displays, c) the influence of observer metamerism can be reduced by the spectral color reproduction, and d) the quantitative spectral attributes of an object, useful for its analysis or recognition, can be captured and preserved. Finally, the effectiveness of the system is also demonstrated through experiments in fields of application, such as medicine, digital archives, color printing, electronic commerce, and computer graphics. |
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Recent Trends in Color Image Watermarking J. Imaging Sci. Technol. Vol. 53, 010201 (Feb 03 2009) Online Publication Date: 03 February 2009
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This article provides a review of the state of the art in watermarking techniques specifically designed for color images. It presents an overview of the color image watermarking methods and an analysis of the advantages and disadvantages of several recent schemes. It also presents solutions and arguments supporting the idea that methods based on human visual sensitivity provide more robust watermarks than do other ones. Furthermore, this article treats the question of the evaluation of watermarking quality according to fidelity. Finally, based on this analysis, research directions in color image watermarking are suggested. |
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Monte Carlo Modeling of Light Scattering in Paper J. Imaging Sci. Technol. Vol. 53, 020201 (Mar 06 2009) Online Publication Date: 06 March 2009
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We introduce a modified Monte Carlo model of light scattering in paper for better understanding of optical dot gain origin. Using a realistic description of paper as a scattering medium and assuming that light distribution in paper (generally any homogeneous or inhomogeneous substrate) depends on its optical properties, we tried to determine light distribution inside paper with known optical properties. In our description, absorption and scattering coefficients of all paper constituents were taken as key functions insofar as they contribute in a real printing application. Due to the fact that paper is a complex medium, it is necessary to involve, in calculations, its surface structure, which was modeled on the base of microfacets. Depicted phenomena were observed and calculated in transmission and reflection. Agreement of the statistical light scattering model in a complex substrate with experimental data demonstrates that the new method successfully describes the phenomena of interest. |
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J. Imaging Sci. Technol. Vol. 52, 050201 (Sep 19 2008) Online Publication Date: 19 September 2008
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Security printing is the use of variable data printing (VDP) to add readable information to printed regions. This is used for brand identification, track and trace, product authentication, and, if applicable, for investigation and evidentiary purposes. Well-crafted, multiregion deterrents can be a powerful means to simultaneously provide readable information and deter would-be counterfeiters through the crafting of difficult-to-reproduce printing effects. This allows the brand owner to select the best printing technology for the deterrents (or for different aspects of a multiregion deterrent), and to gain insight into how the counterfeiter may attempt to reproduce their deterrent with a different printing approach. In this article, repeated line patterns, two-dimensional (2D) bar code reading, and authentication of a color deterrent (color tile) are considered. These features are printed using thermal ink jet (TIJ), dry electrophotography (DEP), and liquid electrophotography (LEP) digital printers. Line patterns and 2D bar code differences are representative of the printer’s binary print quality. Color tiles are representative of the printer’s ability to produce color-based deterrents with fidelity, and are also used to show authentication accuracy on multiple printers and on multiple substrates. Authentication of TIJ printed color tiles is better on glossy paper than on plain office paper, whereas the opposite was observed for DEP printed color tiles. Finally, meaningful metrics for comparison are discussed, including security payload density, deterrent reproducibility, color and spatial frequency fidelity, deterrent precompensation, and the sensitivity of deterrent authentication to image capture settings and devices. |
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J. Imaging Sci. Technol. Vol. 52, 060201 (Dec 11 2008) Online Publication Date: 11 December 2008
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Ink jet technology has advantages such as high-resolution and a multicolor printing capability and has a good potential for computer-based three-dimensional (3D) fabrication. The authors have developed an ink jet 3D bioprinter to manufacture biologically viable 3D structures using living cells. They have developed an effective method for the fabrication of 3D hydrogel structures by using ink jet technology with a liquid aqueous gelating medium, which is essential in fabricating 3D structures with living cells. In the present study, they evaluated the feasibility of the ink jet approach for digital 3D biofabrication, analyzing the microgel beads produced by the ink jet droplets. The ink jet droplets of sodium alginate solution, which were ejected into CaCl2 solution, gelled to form microgel beads. The resulting beads were analyzed by means of image-based particle analysis to show that homogeneously sized microgel beads were effectively produced. Ink jet 3D biofabrication has a high potential for effective digital fabrication with such homogeneous microgel beads and will provide promising approaches for sophisticated computer assisted tissue engineering. |
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Diagnostic Ultrasound Image Enhancement: A Multiscale Permutation Approach J. Imaging Sci. Technol. Vol. 56, 010501 (Mar 15 2012) Online Publication Date: 15 March 2012
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It has been estimated that one out of every four medical diagnosis in the world involves ultrasound imaging modality because of its noninvasive nature, low cost and capability of forming real time imaging. Ultrasonic imaging extends its application to many fields of medical diagnosis, but the utilization is being unfortunately affected by speckle noise. In this article, an efficient multiscale approach is proposed to reduce speckle, to enhance the edge information and to preserve point and linear features, rather than just inhibiting smoothing. With this approach, the image enhancement is made in three steps: First the image is transformed into Laplacian pyramid domain representation. Second, the pyramid coefficients are manipulated by permutated diffusion, and finally the image is reconstructed from the diffused Laplacian pyramid. New permutated diffusion is proposed for coefficient manipulation for effective speckle reduction and enhancement. The proposed permutated diffusion avoids the blocky effects caused by second-order partial differential equation (PDE) and requires only little iteration compared to fourth-order PDE to converge. In each pyramid layer, a gradient threshold is estimated automatically using robust median estimator. The mean absolute error between two adjacent diffusion steps is used as a stopping criterion. Performance of the proposed approach is compared with the state of the art pyramid based methods. Experiments on synthetic data, simulated phantom and real ultrasound data set indicate effective suppression of speckle, preservation of edge information and their structural details.
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Assessment of Color Fringe on Scanned Images J. Imaging Sci. Technol. Vol. 56, 010505 (Mar 14 2012) Online Publication Date: 14 March 2012
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Scanner, as a component of multifunction peripheral or standalone device, is widely utilized for document scanning and copying. There are various image quality attributes affecting performance of scanners. This article is focused on quantitative evaluation of color fringe on scanned images. Based on results of interview with participants in human visual experiments, major attributes affecting perceived degrees of color fringe are selected first. Formulas for selected attributes are defined. Proposed evaluation model is constructed as a linear combination of selected attributes by applying linear regression to values of calculated attributes and just noticeable difference scores by human visual experiments. Experimental results indicate that the calculated measures from the proposed model faithfully match with results of human visual experiments.
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Kubelka-Munk Model for Imperfectly Diffuse Light Distribution in Paper J. Imaging Sci. Technol. Vol. 52, 030201 (Jun 02 2008) Online Publication Date: 02 June 2008
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Perfectly diffuse light is a fundamental assumption in the Kubelka-Munk (KM) model. This assumption is, however, seldom fulfilled by real media. In this work, we build a bridge between a weakly absorbing medium with an imperfectly diffuse light distribution and the corresponding KM model relying on a perfectly diffuse light distribution. We multiply the apparent K and S phenomenal coefficients deduced from a learning set medium by a scaling factor expressing the ratio of light diffuseness between the target medium and the learning set medium. For the target medium, thanks to this diffuseness scaling factor, theoretically predicted reflection and transmission spectra agree with the corresponding measured spectra. The illumination geometry, the optical properties and the thickness of the medium have an impact on the light diffuseness and therefore on the proposed diffuseness scaling factor. |
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J. Imaging Sci. Technol. Vol. 52, 020201 (Apr 10 2008) Online Publication Date: 10 April 2008
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The usefulness of different distance measures in the training phase of self-organizing map (SOM) for color histogram generation for spectral image retrieval purposes is examined. The calculation of the best-matching unit (BMU) in the training phase of SOM is done by using Euclidean distance, Kullback–Leibler distance, Jeffrey divergence, and CIEL*a*b* color difference as distance measures. One-dimensional SOMs are generated for two different data sets consisting of 1269 Munsell color chips and 1, 440, 000 color spectra collected from a real spectral image database. The suitability of the introduced measures is first evaluated by calculating the average color differences between the Munsell data set and its BMUs in the SOMs trained by Munsell data. The achieved results are validated by a practical application, in which the queries from a real spectral image database are performed. Furthermore, the ability of SOMs trained by different distance measures to distinguish between spectral images of real human skin and magazine prints of human skin is examined. The achieved results are promising and indicate that two-dimensional self-organizing maps, which are trained by using Euclidean distance and Jeffrey divergence as distance measure and color histograms that correspond the spectral images as training data, could be used for classifying spectral images. |
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Call for Papers: Focused Section on Digital Fabrication and Functional Printing J. Imaging Sci. Technol. Vol. 56, 010102 (2012)
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Simple Color Prediction Model Based on CIEXYZ Using an Effective Coverage Map J. Imaging Sci. Technol. Vol. 56, 010506 (Mar 14 2012) Online Publication Date: 14 March 2012
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Most of the color prediction models use a single dot gain curve for each primary ink. In the proposed model, the behavior of the dot gain of each primary ink is characterized by three curves based on CIEXYZ tristimulus values. In our previous works, it was shown that the usage of three characterization curves for each primary ink reduced the color difference between the predicted and measured data compared with the simple Yule–Nielsen model. In this article, an effective coverage map based on CIEXYZ is created. This map presents the effective coverage values of the primary inks corresponding to different ink combinations. Given any reference ink combination, the effective coverage values of the involved primary inks are estimated by cubic interpolation. Compared to our previous models, the proposed model gives significant reduction in the color difference between the predicted and the measured data.
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Color Enhancement of Digital Images by Experts and Preference Judgments by Observers J. Imaging Sci. Technol. Vol. 50, 1 (2006) Online Publication Date: 09 May 2006
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We studied the preference judgment of pictorial images by image experts and naive observers. We first asked image experts to improve pictorial images the way they preferred. Then, we showed the different versions of each image to naive observers and asked them which version they preferred. To enhance an image, an expert divides it into large areas of interest, which mainly correspond to natural colors. To assess their preference judgments, naive observers principally focus on natural colors like sky, skin, or grass when present. A closer analysis of the digital image files showed that the segmentation process used by the experts allows to apply different corrections on the different objects. We used the previous work on memory colors by Yendrikhovskij and we showed that, to enhance an image, an expert moves the color space coordinates of identified zones towards those of memory colors corresponding to the objects being represented. The expert also follows some rules: the corrections must be plausible inside each segment and for the whole image, in relation with the illuminant of the scene. The images are accepted by observers in relation with the presence of memory colors and when the treatment of the whole image seems coherent. |
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J. Imaging Sci. Technol. Vol. 50, 320 (2006)
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Considering luminance contrast to comprise the building blocks of the photographic language, we aimed to study the connection between viewer’s contrast discrimination performance in black-and-white photographs with various contrast reproductions, and their aesthetic appeal. In a previous study we examined the viewer’s ability to discriminate contrast increments, applied to discrete regions of the characteristic curves of gray scales versus photographs of Ansel Adams. The photographs belonged to three conceptual categories: portrait, landscape, and architecture. Whereas, contrast discrimination performance in gray scales was very poor in reproductions with altered contrast in the shadows, a significant improvement in performance was observed in the photographs. In the present study subjects performed a contrast preference evaluation task, in which, the reproductions of the photographs were rated for their aesthetic appeal on a five-point scale. The photographs were presented in random order, without indication as to which is the original photograph. Nevertheless, the viewers showed a general preference for photographs with contrast reproductions similar to the original. The results suggest a match between the viewers’ and the photographer’s preferences. Moreover, the preference decreased systematically with the contrast increment for all reproductions. This tendency seems to be independent of variations in category or spatial configuration. The results are in line with the observed contrast discrimination performance, and also consistent with the anchoring theory and recent propositions of biologically based rules for art creation and appreciation as manifestations of the function of the brain.
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Impact of Scrambling on Barcode Entropy J. Imaging Sci. Technol. Vol. 55, 050601 (Nov 02 2011) Online Publication Date: 02 November 2011
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Security barcodes and other barcodes linked to on-line databases have become commonplace due to the increased availability of mobile phones equipped with high-quality cameras. In this article, the authors provide methods for quantifying the entropy of the embedded barcode data, assuming methods other than the standards-specified error-correcting code (ECC) approaches can be adopted. Higher entropy, which reduces the likelihood of a fraudulent agent being able to “guess” correct barcodes, is measured directly using a variety of novel algorithms and applied to large sets of barcodes. The authors data, however, show that removing ECC provides the additional advantage of increasing the entropy. Thus, all other settings (data payload size, printing technology, substrate used, etc.) being equal, eliminating the ECC increases the security of the information content for the barcodes (DataMatrix) tested.
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Spectral Color Reproduction Using an Interim Connection Space-Based Lookup Table J. Imaging Sci. Technol. Vol. 52, 040201 (Jul 15 2008) Online Publication Date: 15 July 2008
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For purposes of defining a feasible approach to spectral color management, previous research proposed an interim connection space (ICS). ICS is relatively low in dimension and would be situated between a high-dimensional spectral profile connection space and output units. The current research simulated printed spectra after using a multidimensional ICS-based lookup tables (LUTs) based on LabPQR, an ICS described in earlier work. LabPQR has three colorimetric dimensions (CIELAB) and additional dimensions to describe a metameric black (PQR). The spectral reproduction accuracies for printing on a six-color ink jet printer were compared based on several versions of the ICS-based LUTs. Variations were evaluated with respect to quality trade-offs between size of the LUT and spectral reproduction accuracies, as well as the number of dimensions necessary for spectral color management. A five-dimensional 17×17×17×5×3 LUT performed well with three dimensions for CIELAB and two dimensions for the PQR metameric black space. This LUT resulted in average CIEDE2000 of 0.51 and average spectral root mean square error of 4.22% for a simulated spectral reproduction of the GretagMacbeth ColorChecker. |
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Image Chain Analysis for Space Imaging Systems J. Imaging Sci. Technol. Vol. 51, 103 (2007) Online Publication Date: 19 April 2007
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Space imaging systems are designed to gather information from vantage points not accessible on Earth. Some systems are designed to look back at the Earth to help us understand our planet better while others are designed to explore the vast universe around us. The diversity of applications between the space imaging systems ensures a new set of engineering challenges with each camera design. The cameras integrated into each space system are designed to meet specific image requirements, but the measure of image quality may be very different depending on the application. For example, Earth-imaging satellites designed for monitoring weather phenomena require high radiometric fidelity whereas Earth-imaging satellites designed for monitoring world events require high spatial resolution for clear visual interpretability. Image chain analysis is used to understand the image formation properties of novel designs and to better understand design trades. Image chain analysis has become an important image science tool for assessing and optimizing image quality in space imaging programs. |
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J. Imaging Sci. Technol. Vol. 56, 010101 (Mar 20 2012) Online Publication Date: 20 March 2012
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Enhancing the Specular Effect of Metallic Color Prints by Reducing the Use of Yellow Ink J. Imaging Sci. Technol. Vol. 55, 060506 (Dec 23 2011) Online Publication Date: 23 December 2011
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The MetallicArt technique is used as a visual security feature to hide patterns in CMY images using an additional silver ink. The patterns are hidden under nonspecular viewing conditions and visible under specular viewing conditions. By varying the amount of silver ink, the authors control the intensity of the specular reflection of the printed pattern. Using a spectral reflection prediction model, they can constrain the maximization of the silver ink (S) in order to keep the color difference between the original CMY color and the fitted CMYS color under a given threshold, ensuring that the pattern is hidden under nonspecular viewing conditions. When the printing device requires the inks to be UV cured, the leafing effect of the silver ink is reduced. This also reduces the specular reflection of the silver ink, which becomes comparable to the specular reflection of the yellow ink. Since both specular reflections are similar, it is difficult to distinguish the embedded patterns under specular viewing conditions when both inks are present. The authors, therefore, propose a new algorithm to embed patterns in CMY images that not only maximizes silver but also minimizes yellow. Experimental results show that the proposed algorithm enhances the visibility of the patterns under specular viewing conditions, allowing the use of MetallicArt when the printing device requires UV curing.
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Spectral Gamut Mapping using LabPQR J. Imaging Sci. Technol. Vol. 51, 473 (2007) Online Publication Date: 20 November 2007
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Spectral color management requires inversion of printer spectral characterizations and necessarily involves the concept of spectral gamut mapping. A printer was spectrally characterized and the spectra were transformed to an interim connection space (ICS), a spectral description space with low dimensionality useful for building lookup tables (LUTs) of feasible sizes. LabPQR is the ICS used. It has separate dimensions describing colorimetry (CIELAB) and a spectrum’s metameric black difference from a standard metamer (PQR). The relationship between digital value and LabPQR was inverted using a single stage objective function combining colorimetric and spectral criteria. The objective function’s colorimetric criterion minimized CIEDE2000 under chosen conditions and its spectral criterion minimized Euclidian distance in PQR coordinates. A weight series was performed to find the optimal trade-off between colorimetric and spectral error. A 1:50 weighting ratio, CIEDE2000 to PQR difference, was deemed best. For the GretagMacbeth ColorChecker, the proposed single stage objective function showed equivalent levels of the performance to a full 31-dimensional unmodified spectra approach, resulting in an average RMS error of 4.18% and an average CIEDE2000 of 0.03. The single stage objective function for spectral gamut mapping using LabPQR proved to be promising for spectral reproduction. |
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