This PDF file contains the front matter associated with SPIE Proceedings volume 7528, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

The presentation provides an update on ongoing research using three-dimensional Colour Mondrians. Two still life arrangements comprising hand-painted coloured blocks of 11 different colours were subjected to two different lighting conditions of a nearly uniform light and directed spotlights. The three-dimensional nature of these test targets adds shadows and multiple reflections, not found in flat Mondrian targets. Working from exactly the same pair of scenes, an author painted them using watercolour inks and paints to recreate both LDR and HDR Mondrians on paper. This provided us with a second set of appearance measurements of both scenes. Here we measured appearances by measuring reflectances of the artist's rendering. Land's Colour Mondrian extended colour constancy from a pixel to a complex scene. Since it used a planar array in uniform illumination, it did not measure the appearances of real life 3-D scenes in non-uniform illumination. The experiments in this paper, by simultaneously studying LDR and HDR renditions of the same array of reflectances, extend Land's Mondrian towards real scenes in non-uniform illumination. The results show that the appearances of many areas in complex scenes do not correlate with reflectance.

Color constancy remains an important subject of research on color standards, computer imaging, and human color vision. There are many different theories and algorithms that interpret and predict constancy. This paper analyzes three different approaches that are frequently discussed separately in the literature: pixel-based colorimetric standards of appearance; computer imaging calculations of an object's reflectance; and calculation of appearance using spatial comparisons. This paper compares and contrasts these approaches. Further, it reviews experiments that measure appearance in color constancy in a variety of situations. A pivotal tool in analyzing models of constancy is the correlation of object's reflectance with appearance. Each approach has different interpretation of this correlation. Using measurements of constancy with particular attention to reflectance, illumination, and appearance helps us to see the successes and limitations of each constancy approach.

This paper describes the investigation and analysis of color terms in modern Japanese. Japanese people use a large vocabulary of color terms in Japanese unconsciously in their daily life. The authors have studied the basic color terms. The color vocabulary was investigated for modern Japanese over 6 years, and in all 2,100 subjects participated in the vocabulary test. This paper shows the investigation process and analyzes the collected color vocabularies from various points of view. The vocabulary test is based on a questionnaire format without showing any color samples, where each subject was requested to answer the question items for color names in two levels of importance. Therefore we collected their recall color names without a priori clue such as color samples. The frequency of occurrence of the responded color names is statistically evaluated, and then the importance of color names is analyzed from various points of view.

The present study investigates the tendency of individuals to categorize colors. Humans recognize colors by categorizing them with specific color names such as red, blue, and yellow. When an individual having a certain type of color vision observes an object, they categorize its color using a particular color name and assume that other people will perceive the color in an identical manner. However, there are many variations in human color vision caused by photoreceptor differences in the eye, including red and green confusion. Thus, another person with a different type of color vision may categorize the color using another name. To address this issue, we attempt to determine the differences in the ranges of colors that people with different types of color vision categorize using particular color names. In the modern urban environment, most visual information, including warning signs and notice boards, is coded by color. Finding the common color categories among different types of color vision is an important step towards achieving Color Universal Design, a visual communication method that is viewer-friendly irrespective of color vision type. Herein we report on a systematic comparison between people with common (C-type) and deutan (D-type) color vision. Analysis of protan (P-type) color vision will follow in a subsequent report.

Perceived image contrast is one of the major factors affecting the image quality on displays. Various methods have been proposed to measure the image contrast. However, image contrasts in most of previous works are focused on B/W and defined on simple patterns such as sinusoidal grating. This paper introduces a perceived contrast evaluation model for natural color images. In pursuit of high accuracy, both global and local contrasts are taken into account. Global contrast indicates difference in the perceived luminance and chroma. Local contrast describes the distinguishable degree in image details. In the proposed method, global contrast is calculated based on the dynamic ranges in lightness and chroma. Local contrast is obtained by gradient computations. Both of the global and local contrasts are merged to achieve the perceived contrast. Two types of performance evaluations are performed. They are cross content and within content evaluations. Results of experiments show that global contrast is more effective in the cross content evaluation where the contrast differences between different natural color images are examined. For both of the cross and within content evaluations, the proposed measure yields high value of correlation coefficient with the subjective scores from human visual tests.

Age influences all bodily functions, also vision. Therefore, the effects of age on vision should be mirrored in ergonomic requirements laid down in display standards such as ISO 9241-300/307, 'Electronic visual display requirements'. However, this is only true to a limited extent - just as is the case with other standards dealing with ergonomic requirements, because developers of such standards do not possess the necessary specific knowledge. It therefore was an important step by ISO and IEC to publish in 2001 ISO/IEC Guide 71: 'Guidelines for standard developers to address the needs of older persons and persons with disabilities'. This guide was followed by a more specific and detailed Technical Report from ISO, ISO/TR 22411, as well as by 'Guidelines on Accessibility' from CIE. These three guidelines are reviewed. The paper concludes with developments around ISO 9241-300/307 in general, especially future additions on autostereoscopic displays and electronic paper. As to the former, the visual fatigue often accompanying viewing 3D displays needs methods for characterizing and validating such displays, to reduce visual fatigue as much as possible. Standardizing certain properties of electronic paper is an example of the present pro-active way of working of ISO/TC159/SC4/WG2, 'Visual Display Requirements', that developed ISO 9241-300/307.

Colour preference adjustment is an essential step for colour image enhancement and perceptual gamut mapping. In colour reproduction for pictorial images, properly shifting colours away from their colorimetric originals may produce more preferred colour reproduction result. Memory colours, as a portion of the colour regions for colour preference adjustment, are especially important for preference colour reproduction. Identifying memory colours or modelling the memory colour region is a basic step to study preferred memory colour enhancement. In this study, we first created gamut for each memory colour region represented as a convex hull, and then used the convex hull to guide mathematical modelling to formulate the colour region for colour enhancement.

This paper proposes a method for real-time color measurement using active illuminant. A synchronous measurement system is constructed by combining a high-speed active spectral light source and a high-speed monochrome camera. The light source is a programmable spectral source which is capable of emitting arbitrary spectrum in high speed. This system is the essential advantage of capturing spectral images without using filters in high frame rates. The new method of real-time colorimetry is different from the traditional method based on the colorimeter or the spectrometers. We project the color-matching functions onto an object surface as spectral illuminants. Then we can obtain the CIE-XYZ tristimulus values directly from the camera outputs at every point on the surface. We describe the principle of our colorimetric technique based on projection of the color-matching functions and the procedure for realizing a real-time measurement system of a moving object. In an experiment, we examine the performance of real-time color measurement for a static object and a moving object.

Historically, in the 35 years of digital printing research, raster image processing has always lagged behind marking engine technology, i.e., we have never been able to deliver rendered digital pages as fast as digital print engines can consume them. This trend has resulted in products based on throttled digital printers or expensive raster image processors (RIP) with hardware acceleration. The current trend in computer software architecture is to leverage graphic processing units (GPU) for computing tasks whenever appropriate. We discuss the issues for rendering fonts on such an architecture and present an implementation.

In this changing environment in which the artist and designer has access to a wide range of digital imaging tools and technologies, that on first glance, are dedicated to the creation of colour mixtures, why is the digital interface and colour outcome often disappointing? It appears that hardware, software tools and methods for digital printing are not necessarily suited to the specific requirements of the artist. In fact, they are too generalised to obtain a high degree of quality and too inflexible to allow artists to obtain precision and predictability. Is it possible for an artist to mix and print a colour that captures their creative imagination? The motivation for this research is based on how artists mix and print colour by traditional means (painting and printmaking) and how these differ from colour picker tools, slider bars and methods developed for digital printing, and whether it is possible to incorporate both? The paper provides a brief historical background to artists who have developed colour systems to assist their particular colour choices. Based on existing hardware and software, the paper suggests alternative approaches to colour selection, demonstrates methods for the creation of novel inkjet printed palettes, and how these can be visualised and compared.

Misalignment between the color planes used to print color images creates undesirable artifacts in printed images. Color trapping is a technique used to diminish these artifacts. It consists of creating small overlaps between the color planes, either at the page description language level or the rasterized image level. Existing color trapping algorithms for rasterized images trap pixels independently. Once a pixel is trapped, the next pixel is processed without making use of the information already acquired. We propose a more efficient strategy which makes use of this information. Our strategy is based on the observation of some important properties of color edges. Combined with any existing algorithm for trapping rasterized images, this strategy significantly reduces its complexity. We implement this strategy in combination with a previously proposed color trapping algorithm (WBTA08). Our numerical tests indicate an average reduction of close to 38% in the combined number of multiplications, additions, and "if" statements required to trap a page, as compared with WBTA08 by itself.

Screen or halftone pattern appears on the majority of images printed on electrophotographic and ink-jet printers as well as offset machines. When such halftoned image is scanned, a noisy effect called a Moiré pattern often appears on the image. There are plenty of methods proposed for descreening of images. Common way is adaptive smoothing of scanned images. However the descreening techniques face the following dilemma: deep screen reduction and restoration of contone images leads to blurring of sharp edges of text and other graphics primitives, on the other hand insufficient smoothing keeps screen in halftoned areas. We propose novel descreening algorithm that is primarily intended for preservation of sharpness and contrast of text edges and for restoration contone images from halftone ones accurately. Proposed technique for descreening of scanned images comprises five steps. The first step is decrease of edge transition slope length via local tone mapping with ordering; it is carried out before adaptive smoothing, and it allows better preservation of edges. Adaptive low-pass filter applies simplified idea of Non-Local Means filter for area classification; similarity is calculated between central block of window and different adjacent block that is selected randomly. If similarity is high then current pixel relates to flat region, otherwise pixel relates to edge region. For prevention of edges blurring, flat regions are smoothed stronger than edge regions. By random selection of blocks we avoid the computational overhead related to excessive directional edge detection. Final three stages include additional decrease of edge transition slope length using local tone mapping, increase of local contrast via modified unsharp mask filter, that uses bilateral filter with special edge-stop function for modest smoothing of edges, and global contrast stretching. These stages are intended to compensate decreasing of sharpness and contrast due to low-pass filtering, it allows to enhance visual quality of scanned image. For parameters adjusting for different scanning resolutions and comparison with existing techniques test target and criteria were proposed. Also the quality of proposed approach is evaluated by surveying observer's opinions. According to obtained outcomes the proposed algorithm demonstrates good descreening capabilities.

This paper proposes a spectral matching imager with a novel three-phase quadrature detection method. The proposed imager consists of the time-domain correlation image sensor (CIS) and a high-speed programmable spectral light source (PSLS) to produce the correlations between each of a quadrature pair of reference spectral functions and spectral functions of objects. This is realized by modulating the object spectra into temporal signals with the PSLS and then producing temporal correlations with reference signals at each pixel of the CIS. The object that has the same spectral function as the target spectral function is detected as a vector with an azimuthal angle of zero projected onto the two-dimensional (2-D) space spanned by the reference spectral functions. The proposed method can estimate the correlation coefficient between the object and reference spectra more reliably in a 2-D space than previous 1-D spectral matching methods, by factoring out the norm of the object spectral function. Experimental results for a color chart confirm the effectiveness of the proposed method.

In these days, most of cellular phones have built-in digital camera. As number of pixels approaches to that of digital still cameras, consumer's expectation of image quality taken by cellular phone camera is increasing. Automatic white balance is a function to provide illuminant independent image quality. In this paper, a new automatic white balance method suitable for cellular phone is proposed. Camera images are divided into three categories. They are first classified as images with dominant color or images with variety of colors. Images having variety of colors are further divided into two subclasses based on the existence of highlight area; images with and without highlight regions. Three different AWB techniques are designed and applied to each of three classes. Experimental results indicate that the proposed technique yields better performance than the conventional methods.

In this paper, we propose a simple method for wine color characterization, classification and reproduction. The aim is to represent the colors of wines with limited number of hues that we call nuances. Burgundy wines (France) constitute the wine samples in this study but the method remains general. The method consists of four steps: spectral transmittance measures of a large number of wine samples. Then standard and gamma corrected colors are reconstructed from spectral data. Afterwards, a ΔE-based classification is performed in the CIELAB, which provides good visual uniformity and thus offers the best discrimination between the different samples. The last step is a spectral-based color reproduction using synthetic liquids. The obtained results are encouraging in that they permit an accurate characterization and reproduction of wine color.

Several color-imaging algorithms such as color gamut mapping to a target device and resizing of color images have traditionally involved pixel-wise operations. That is, each color value is processed independent of its neighbors in the image. In recent years, applications such as spatial gamut mapping have demonstrated the virtues of incorporating spatial context into color processing tasks. In this paper, we investigate the use of locally based measures of image complexity such as the entropy to enhance the performance of two color imaging algorithms viz. spatial gamut mapping and content-aware resizing of color images. When applied to spatial gamut mapping (SGM), the use of these spatially based local complexity measures helps adaptively determine gamut mapping parameters as a function of image content - hence eliminating certain artifacts commonly encountered in SGM algorithms. Likewise, developing measures of complexity of color-content in a pixel neighborhood can help significantly enhance performance of content-aware resizing algorithms for color images. While the paper successfully employs intuitively based measures of image complexity, it also aims to bring to light potentially greater rewards that may be reaped should more formal measures of local complexity of color content be developed.

Contrary to high dynamic range imaging, the preservation of details and the avoidance of artifacts is not explicitly considered in popular color management systems. An effective way to overcome these difficulties is image filtering. In this paper we investigate several image filter concepts for detail preservation as part of a practical gamut mapping strategy. In particular we define four concepts including various image filters and check their performance with a psycho-visual test. Additionally, we compare our performance evaluation to two image quality measures with emphasis on local contrast. Surprisingly, the most simple filter concept performs highly efficient and achieves an image quality which is comparable to the more established but slower methods.

Even though gamut mapping (GM) is a three-dimensional polyhedron problem, algorithmically it is usually not treated as such. This is due to tight runtime constraints in practice, which suggest simple algorithms. We will show that basic geometric operations, like the intersection of a ray with the gamut surface, can be implemented very efficiently for typical GM applications that work with device gamuts. This opens up new possibilities to design algorithms without reducing their practicability.

The Technical Committee 1-55 of the CIE on "Uniform color space for industrial color difference evaluation" requested in 2007 reliable experimental datasets (that is, color pairs assessed by a considerable number of observers with nondefective color vision, under well controlled experimental conditions and using proper experimental methods). The aim was to use these datasets to develop/test new color spaces with Euclidean color-difference formulas more robust than the CIEDE2000 color-difference formula. The objective of this paper is to propose a new dataset more reliable than previous datasets and to evaluate from this dataset more accurate just noticeable differences. In our study we have considered not only surface specimens (reflective objects), but also mainly color pairs assessed using visual displays (e.g., self-luminous LCD). Our experimental results have been obtained under illuminating/viewing conditions close to the "reference conditions" suggested for the CIEDE2000 color-difference formula (CIE Publication 142-2001) and by the ISO standard 3668:2003 (ISO standard 3668:2003 Paints and varnishes - Visual comparison of the colour of paints).

Spectral distribution can be written as a linear combination of eigenvectors and the eigenvectors method gives the least estimation error, but eigenvectors depend on a sample selection of population and encoding values have no physical meaning. Recently reported LabPQR [1] is to convey physical values, but still is dependent on a sample selection of population. Thus, LabRGB [2] was proposed in 2007. LabRGB is to provide "sample selection of population" free spectral encoding/decoding methods. LabRGB consists of six unique trigonometric base functions and physically meaningful encoding values. LabRGB was applied to the real multispectral images and showed almost equal performance to traditional orthogonal eigenvector method in spectral estimation, and even better performance in colorimetric estimation. In this paper, the weighting factors of the base functions were examined in terms of their possible ranges. The numerical values are obtained by using a linear programming technique, and the results are also confirmed by using the Monte Carlo method. The results indicate that the possible ranges of six scores for six base functions are well within -80 to 80. The ranges thus obtained give a good clue for explicitly defining the bit depths of respective scores for the future applications and standardization.

Imaging techniques have been developed to better account for fluorescent emission that may accompany reflected light during capture and processing of high color-fidelity imagery from art works and important historical documents. This approach is based on sequential capture of monochrome images of the object or scene, each illuminated by a narrow spectral band from a bank of light-emitting diodes (LED's) in the ultraviolet, visible, and near-infrared spectral regions. These images contain color reference materials in the field of view, and are augmented by images in which bandpass filters are placed in the capture path. Processing of these images allows the separate contributions of reflectance and fluorescence emission in narrow wavelength bands to be recognized and quantified, which allows accounting for any fluorescence contributions during nominal reflectance imaging so that adjustments may be made in subsequent rendering. This paper describes the apparatus, capture procedures, and processing techniques that are employed. The impact of fluorescence on color fidelity during reproduction, based on deltaE calculations, is calculated and discussed for highly fluorescent pastels.

A common problem for all color displays, regardless of whether they are of the self-luminous or non-self-luminous type, is the synthesis of a full-color image from a limited set of primary colors. Several approaches to color synthesis have been employed for electronic displays. The most successful of these conform to the principles of additive color mixture and include optical superposition, spatial synthesis and temporal synthesis. In order to understand the principles of color generation in electronic display systems, as well as the relative strengths and weaknesses of synthesizing color in the space and time domains, I first consider the visual bases which allow such color synthesis to occur. Although basic approaches to color synthesis have served the evolution of display technology well up to recent times, I present the argument that the continued evolution of display technology toward higher display resolution and enhanced color quality has exposed the limitations of both spatial color synthesis and temporal color synthesis and raises questions as to whether either method for synthesizing color can alone fully satisfy the ever increasing demands on display image quality. Clearly, new approaches to color synthesis are needed to sustain the evolution of display technology, and I describe recent concepts with the potential for pushing the horizons of color display image quality and reducing the costs of future color displays. These include hybrid spatial-temporal color synthesis and 3D color synthesis as well as variants of these approaches.

The YCbCr color space in BT.709 suffers the image quality deterioration by color difference signal sub-sampling though reducing the number of signals are quite important issue for future television system. For the future television systems, such as UHDTV and 3DTV, new color encoding space is required which can encode large color gamut and result in good image quality even after color difference signal sub-sampling. In this study, two approaches i.e. following human visual system (CIECAM02) and using new sets of wide color gamut primaries are considered to design new color encoding space. Various YCC color encoding spaces are designed and the sub-sampled image qualities are compared. The result shows that using the opponent color signals in simplified-CIECAM02 as YCC space has the best image quality. Also it is shown that using wide color gamut primaries can improve the sub-sampled image quality significantly than the current encoding color space for HDTV.

3D-LCD technology is beginning to become popular in video entertainment display devices. For ultimate viewing experience it appears attractive to better understand the influence of color within 3D scenery with regard to visual perception of shape and depth. To facilitate such a task, 3D graphics renderers offer a suitable experimental approach. Enabling comparison of simple synthetic scenarios when combining 3D-modeling and color component synthesis one can also extend it to naturally looking scenarios. Consequently, relevant color parameter modifications carried out successively and independently may lead to optimal discrimination of their influence. Taking into account mathematical color mapping techniques that are based on mapping 3-dimensional color space into monochromatic space we address valuable findings such as subtle blue shifts in aerial perspective (due to light scattering) often reported by artists as important visual cues. After searching for counter-proofs that efficiently define contradiction associated with each parameter one can predict influence of color in relative quantities with regard to depth cues. Further experiments focus on color dependent depth perception of an object moving within synthetic or natural scenarios. Applying synthetic objects in such scenarios we searched for visually perceived depth locations as a function of object color. Subsequently, a comparison of color dependent depth perception between static objects and motion objects is also discussed.

In current printing technique, the Color Management System uses the ICC profiles of monitor and printer to perform color matching. Unfortunately the ICC profile cannot capture all of the monitor color reproduction characteristics, because such features change when the user acts on the color temperature, brightness and contrast controls, and they also depend on the kind of backlighting and lifetime of LCD monitor. As a result there is usually an unwanted color difference between an image displayed on the user monitor and its printed version. Yet, once we are able to produce an ICC profile that matches the user's monitor characteristics by measuring, then the CMS becomes able to correctly perform color matching. However, this method is of difficult application, because in general the measuring equipment is not available and, even then, it takes a long time and new measurements according to monitor color temperature, brightness and contrast. In this paper we propose a color matching technique based on estimate of the user's environment through the simple visual test with an output image on monitor and its printed image. The estimated characteristic of monitor is stored in new ICC profile and applied to color conversion process. Consequently the proposed method reduced the color difference between image displayed on user monitor and its printed image.

With the advent of high dynamic range imaging and wide gamut color spaces, gamut mapping algorithms have to nudge image colors much more drastically to constrain them within a rendering device's gamut. Classical colorimetry is concerned with color matching and the developed color difference metrics are for small distances. For larger distances, categorization becomes a more useful concept. In the gamut mapping case, lexical distance induced by color names is a more useful metric, which translates to the condition that a nudged color may not cross a name boundary. The new problem is to find these color name boundaries. We compare the experimental procedures used for color naming by linguists, ethnologists, and color scientists and propose a methodology that leads to robust repeatable experiments.

Hierarchical Error Diffusion (HED) developed in [14] yields high-quality color halftone by explicitly designing three critical factors: dot overlapping, positioning, and coloring. However, HED requires more error memory buffer than the conventional error diffusion algorithms since the pixel error is diffused in dot-color domain, instead of colorant domain. This can potentially be an issue for certain low-cost hardware implementation. This paper develops a memory-efficient HED algorithm (MEHED). To achieve this goal, the pixel error in dot-color domain is converted backward and diffused to future pixels in input colorant domain, say, CMYK for print applications. Since the error-augmented pixel value is no longer bounded within the range [0, 1.0], the dot overlapping control algorithm developed in [14] needs to be generalized to coherently handle the pixel density of outside the normal range. The key is to carefully split the modified pixel density into three parts: negative, regular, and surplus densities. The determination of regular and surplus densities needs to be dependent on the density of K channel, in order to maintain local color and avoid halftone texture artifact. The resulting dot-color densities are serves as the input to hierarchical thresholding and coloring steps to generate final halftone output. Experimental results demonstrate that MEHED achieves similar image quality compared to HED.

A framework for clustered-dot color halftone watermarking is proposed. Watermark patterns are embedded in the color halftone on per-separation basis. For typical CMYK printing systems, common desktop RGB color scanners are unable to provide the individual colorant halftone separations, which confounds per-separation detection methods. Not only does the K colorant consistently appear in the scanner channels as it absorbs uniformly across the spectrum, but cross-couplings between CMY separations are also observed in the scanner color channels due to unwanted absorptions. We demonstrate that by exploiting spatial frequency and color separability of clustered-dot color halftones, estimates of the individual colorant halftone separations can be obtained from scanned RGB images. These estimates, though not perfect, allow per-separation detection to operate efficiently. The efficacy of this methodology is demonstrated using continuous phase modulation for the embedding of per-separation watermarks.

In this paper we describe a method using duplex printing on transparencies to create auto-stereoscopic images viewed in a "see-through" manner. By choosing different halftone structures, differing by having different spatial frequencies for each of the two sides of a transparency, a moire pattern resulting due to halftone overlapping can be observed. On one side of the transparency is provided a uniform halftone with a selected median spatial frequency f. On the other side, the printing consists of two partitions: what is to be perceived as the background is printed using a halftone with spatial frequency equal to the median frequency f plus some ▵f, while a desired image partition is printed using a halftone with a spatial frequency equal to the median frequency f minus the same ▵f. The spatial frequency difference between the halftones on two sides creates a corresponding shift-magnification factor M. The moire produced by the two partition print images as visually located appear in two separate spatial planes as separated by the transparency, with an amplified total depth of the shift-magnification factor M times the thickness of the transparency. This yields a moire stereoscopic pattern for the desired image partition as clearly discernable to the human eye with out aid of lenses or other means.

Most halftoning algorithms assume there is no interaction between neighboring dots or if there is, it is additive. Without accounting for dot-gain effect, the printed image will not have the appearance predicted by the halftoning algorithm. Thus, there is need to embed a printer model in the halftoning algorithm which can predict such deviations and develop a halftone accordingly. The direct binary search (DBS) algorithm employs a search heuristic to minimize the mean squared perceptually filtered error between the halftone and continuous-tone original images. We incorporate a measurementbased stochastic model for dot interactions of an electro-photographic printer within the iterative DBS binary halftoning algorithm. The stochastic model developed is based on microscopic absorptance and variance measurements. We present an efficient strategy to estimate the impact of 5×5 neighborhood pixels on the central pixel absorptance. By including the impact of 5×5 neighborhood pixels, the average relative error between the predicted tone and tone observed is reduced from around 21% to 4%. Also, the experimental results show that electrophotography-model based halftoning reduces the mottle and banding artifacts.

Individual halftone color separations must possess a low degree of distortion to avoid undesirable moiré in the overlays that produce the process colors. Achieving low relative distortion requires precise registration between the exposure devices used to write the halftone separations. However, optical and mechanical errors within the multiple Raster Output Scanners (ROS's) or image bars of a printer result in differences in the trajectory and placement of the exposure spots among color planes. In this paper, color halftone moiré due to ROS errors is analyzed using a frequency vector representation of color halftones. We analyze three forms of process-direction distortion: skew, shear, and bow. Each distortion is inspired from a practical printing system (i.e. while shear and bow are observed in ROS systems, skew is observed in image bar imaging systems). The frequency vector formalism is used to derive bounds on distortion for a classical halftone screen configuration (square cell equal frequency halftones at 15°, 45°, and 75°). The bounds are examined for distortion of one halftone screen and the analysis can be readily applied to distortion of multiple screens. The bounds can be used to develop specifications for imaging components in the design of a ROS or image bar imaging system.

Printers employing electrophotographic technology typically use clustered-dot screening to avoid potential artifacts caused due to unstable dot rendering. Periodic clustered-dot screens are quite smooth, but also suffer from periodic moire artifacts due to interference with other color channels. Stochastic, clustered-dot screens provide an alternative solution. In this paper, we introduce a new approach for stochastic, clustered-dot halftoning and screen design based on direct binary search. The method deviates from conventional DBS in its use of different filters in different phases of the algorithm. We provide an intuitive explanation for the clustering achieved as a result of this modification, and also discuss ways to control the coarseness of clusters. Due to the non-applicability of conventional screen design procedures to the new halftoning method, we propose a new method for screen design also. Results include images of individually designed constant-tone halftones and halftones of screened folded ramps.

The object of this paper majors in the research of 8-electrode oil-water two-phase flow electrical capacitance tomography system. The distribution models of transducer's field are established by the finite element method for the influence of the parameters of transducer's structure on the performance of transducer. The analyses of simulation and experiment and the transducer's design optimized are done, and the measure function of transducer's design optimized is proposed based on transducer parameters. The system of 8-electrode oil-water two-phase flow electrical capacitance tomography is designed based on the results of theory and simulation analyses. The sensitivity and uniformity of sensitive field is improved and the design of the measurement circuit is easier but the data precision of sensitive field is enough for image reconstruction.

Color schemes have been used in maps to visually distinguish different regions or to approximately represent the magnitude of a property. Since human eyes are not able to translate a color to a numerical scale, colors on a traditional map can only be used to visually estimate magnitudes. As maps are represented more and more digitally, a properly designed color scheme may be able to use color to encode numbers and to accurately translate colors into numerical scales of a property. As a mouse (or other pointers) points to a location, the color of the location can be translated into the original encoded number and therefore the numerical property of the location may be displayed. In this paper, method to encode information in digital maps using color schemes is investigated. A hue-based color scheme was developed to encode and decode numerical scales for digital maps. Color gamut issues between display and print are investigated as well.