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In order for a smartphone-based colorimetry system to be generalizable, it must be possible to account for results from multiple phones. A move from device-specific space to a device independent space such as XYZ space allows results to be compared, and means that the link between XYZ values and the physical parameter of interest needs only be determined once. We compare mapping approaches based on calibration data provided in image metadata, including the widely used open-source software dcraw, to a separate calibration carried out using a colorcard. The current version of dcraw is found to behave suboptimally with smartphones and should be used with care for mapping to XYZ. Other metadata approaches perform better, however the colorcard approach provides the best results. Several phones of the same model are compared and using an xy distance metric it is found that a device-specific calibration is required to maintain the desired precision.

A smartphone app to screen for neonatal jaundice has a large potential impact in reducing neonatal death and disability. Our app, neoSCB, uses a colour measurement of the sclera to make a screening decision. Although there are numerous benefits of a smartphone-based approach, smartphone colour measurement that is accurate and repeatable is a challenge. Using data from a clinical setting in Ghana, we compare sclera colour measurement using an ambient subtraction method to sclera colour measurement using a standard colour card method, and find they are comparable provided the subtracted signal-to-noise ratio (SSNR) is sufficient. Calculating a screening decision metric via the colour card method gave 100% sensitivity and 69% specificity (n=87), while applying the ambient subtraction method gave 100% sensitivity and 78% specificity (SSNR>3.5; n=50).

Jaundice is a major cause of mortality and morbidity in the newborn. Globally, early identification and home monitoring are significant challenges in reducing the incidence of jaundice-related neurological damage. Smartphone cameras are promising as colour-based screening tools as they are low-cost, objective and ubiquitous. We propose a novel smartphone method and app called neoSCB to screen for neonatal jaundice by imaging the sclera. It does not rely on colour calibration cards or accessories, which may facilitate its adoption at scale and in less economically developed regions. Our approach is to explicitly address three confounding factors in relating colour to jaundice: (1) skin pigmentation, (2) ambient light, and (3) camera spectral response. (1) The variation in skin pigmentation is avoided by imaging the sclera. (2) With the smartphone screen acting as an illuminating flash, a flash/ no-flash image pair is captured using the front-facing camera. The contribution of ambient light is subtracted. (3) This permits a device-and ambient-independent measure of sclera chromaticity following a one-time calibration. We introduce the concept of Scleral-Conjunctival Bilirubin (SCB), in analogy with Transcutaneous Bilirubin (TcB). The scleral chromaticity is mapped to an SCB value. A pilot study was conducted in the UCL Hospital Neonatal Care Unit. 51 neonates were imaged using the neoSCB app and had a blood test for total serum bilirubin (TSB). The better of two models for SCB based on ambient-subtracted sclera chromaticity achieved r = 0.75 (p250μmol/L (area under receiver operating characteristic curve, AUROC, 0.86), and 92% (specificity 67%) in identifying newborns with TSB>205μmol/L (AUROC 0.85). These results are comparable to modern transcutaneous bilirubinometers.

Background Medication non-adherence in bipolar disorder is a significant problem resulting in increased morbidity, hospitalisation and suicide. Interventions to enhance adherence exist but it is not clear how effective they are, or what works and why. Methods We systematically searched bibliographic databases for RCTs of interventions to support adherence to medication in bipolar disorder. Study selection and data extraction was performed by two investigators. Data was extracted on intervention design and delivery, study characteristics, adherence outcomes and study quality. The meta-analysis used pooled odds ratios for adherence using random effects models. Results Searches identified 795 studies, of which 24 met the inclusion criteria, 18 provided sufficient data for meta-analysis. The pooled OR was 2.27 (95% CI 1.45–3.56) equivalent to a two-fold increase in the odds of adherence in the intervention group relative to control. Smaller effects were seen where the control group consisted of an active comparison and with increasing intervention length. The effects were robust across other factors of intervention and study design and delivery. Limitations Many studies did not report sufficient information to classify intervention design and delivery or judge quality and the interventions were highly variable. Therefore, the scope of moderation analysis was limited. Conclusions Even brief interventions can improve medication adherence. Limitations in intervention and study design and reporting prevented assessment of which elements of adherence support are most effective. Applying published guidance and quality criteria for designing and reporting adherence interventions is a priority to inform the implementation of cost-effective adherence support.

Jaundice is a major cause of mortality and morbidity in the newborn. Globally, early identification and home monitoring are significant challenges in reducing the incidence of jaundice-related neurological damage. Smartphone cameras are promising as colour-based screening tools as they are low-cost, objective and ubiquitous. We propose a novel smartphone method to screen for neonatal jaundice by imaging the sclera. It does not rely on colour calibration cards or accessories, which may facilitate its adoption at scale and in less economically developed regions. Our approach is to explicitly address three confounding factors in relating colour to jaundice: (1) skin pigmentation, (2) ambient light, and (3) camera spectral response. (1) The variation in skin pigmentation is avoided by imaging the sclera. (2) With the smartphone screen acting as an illuminating flash, a flash/ no-flash image pair is captured using the front-facing camera. The contribution of ambient light is subtracted. (3) In principle, this permits a device- and ambient-independent measure of sclera chromaticity following a one-time calibration. We introduce the concept of Scleral-Conjunctival Bilirubin (SCB), in analogy with Transcutaneous Bilirubin (TcB). The scleral chromaticity is mapped to an SCB value. A pilot study was conducted in the UCL Hospital Neonatal Care Unit (n = 37). Neonates were imaged using a specially developed app concurrently with having a blood test for total serum bilirubin (TSB). The better of two models for SCB based on ambient-subtracted sclera chromaticity achieved r = 0.75 (p250μmol/L (area under receiver operating characteristic curve, AUROC, 0.86), and 92% (specificity 67%) in identifying newborns with TSB>205μmol/L (AUROC 0.85). These results are comparable to modern transcutaneous bilirubinometers.

Spectral and 3D imaging techniques are used for museum imaging and cultural heritage documentation providing complementary information to aid in documenting the condition, informing the care, and increasing our understanding of objects. Specialised devices for spectral and 3D imaging may not be accessible for many heritage institutions, due to cost and complexity, and the modification of a consumer digital camera presents the potential of an accessible scientific tool for 2D and 3D spectral imaging. Consumer digital cameras are optimised for visible light, colour photography, but the underlying sensor is inherently sensitive to near ultraviolet, visible, and near infrared radiation. This research presents the characterisation of a modified camera to investigate the impact of the modification on the spectroradiometric and geometric image quality with the intention of the device being used as a scientific tool for cultural heritage documentation. The characterisation includes the assessment of 2D image quality looking at visual noise, sharpness, and sampling efficiency using the target and software associated with the Federal Agencies Digitization Guidelines Initiative. Results suggest that these modifications give rise to discrepancies in computed surface geometries of the order of ± 0.1 mm for small to medium sized objects used in the study and recorded in the round (maximum dimension 20 cm). Measuring the spectral response quantifies the modified camera as a scientific device for more accurate measurements and provides indications of wavelengths that could improve documentation based on sensitivity. The modification of a consumer digital camera provides a less expensive, high-resolution option for 2D and 3D spectral imaging.

Conservation of the painted ceiling at the historic Hampton Court Palace requires the condition of the ceiling to be monitored for signs of formation of cracks and flakes in the surface. Miniature monochrome cameras and LED lights were mounted on a horizontal bar, and raised by a telescopic mast to 60 cm below the ceiling. Images from the cameras were captured simultaneously by purposedeveloped software in a laptop computer at floor level. A series of image pairs was acquired at each location, rotating the mast between each pair. Images were enhanced in local contrast by a modified Wallis filter. From the image set a dense and accurate point cloud was generated, using a photogrammetric bundle adjustment procedure, from which 3D surface details could be visualised.

Polished metallic surfaces exhibit a high degree of specularity, which makes them difficult to reproduce accurately. We have applied two different techniques for modelling a heritage object known as the Islamic handbag. Photogrammetric multi-view stereo enabled a dense point cloud to be extracted from a set of photographs with calibration targets, and a geometrically accurate 3D model produced. A new method based on photometric stereo from a set of images taken in an illumination dome enabled surface normals to be generated for each face of the object and its appearance to be rendered, to a high degree of visual realism, when illuminated by one or more light sources from any angles. The specularity of the reflection from the metal surface was modelled by a modified Lorentzian function.

To be convincing, digital heritage needs to represent physical objects and render them in a way that looks realistic when viewed on a display screen. The problem is difficult enough for flat 2D objects viewed under arbitrary sources of illumination, but is much harder for 3D objects with curved surfaces of diverse materials, especially with varying degrees of sheen or gloss. A new method is presented for estimating the reflectance distribution function from a set of images taken in an illumination dome. Surface normals and albedo are calculated by regression over a subset of the intensity at each pixel. The ratio of actual intensity to diffuse intensity enables the direction of peak specularity to be determined. Then the distribution of specular intensity is modelled as a modified Lorentzian function of radial angle from the specular peak direction, with circular cross section for isotropic surfaces and elliptical cross section for anisotropic surfaces. Fitting the results over the image enables a characteristic RDF (a two-dimensional subset of the BRDF for fixed viewing direction) to be estimated. Rendering the surface by a model that adds the body colour (diffuse) and specular (glistening) components at each pixel for any direction of incident illumination is shown to provide a good simulation of the appearance of the original object.

Low cost monochrome camera systems based on CMOS sensors and C-mount lenses have been successfully applied to a wide variety of metrology tasks. For high accuracy work such cameras are typically equipped with ring lights to image retro-reflective targets as high contrast image features. Whilst algorithms for target image measurement and lens modelling are highly advanced, including separate RGB channel lens distortion correction, target image circularity compensation and a wide variety of detection and centroiding approaches, less effort has been directed towards optimising physical target image quality by considering optical performance in narrow wavelength bands. This paper describes an initial investigation to assess the effect of wavelength on camera calibration parameters for two different camera bodies and the same ‘C-mount’ wide angle lens. Results demonstrate the expected strong influence on principal distance, radial and tangential distortion, and also highlight possible trends in principal point, orthogonality and affinity parameters which are close to the parameter estimation noise level from the strong convergent self-calibrating image networks.

The purpose of this study is to examine the importance that real patients attach to their right to withdraw from an on-going feasibility randomised trial (RCT) evaluating types and timings of breast reconstruction (two parallel trials) following mastectomy for breast cancer. Our results show that, while some respondents appreciated that exercising the right to withdraw would defeat the scientific objective of the trial, some patients with a surgical preference consented only given the knowledge they could withdraw if they were not allocated to their preferred treatment.

A photogrammetric technique was developed to monitor a painted heritage ceiling for evidence of cracking and flaking. A rig with up to four miniature cameras with lighting was raised 8m on a telescopic mast to within 60cm of the ceiling. Sets of images were analysed by a multiview stereo technique to extract point clouds from which a 3D representation of the surface could be obtained. The factor limiting the performance of the system was found to be not image processing but the mechanical characteristics of the telescopic mast.

We aimed to assess and quantify parental beliefs regarding ketogenic dietary therapies (KDTs). We also aimed to determine whether beliefs were related to response to KDTs. Adapted versions of the Beliefs about Medicine Questionnaire were completed by parents of children following KDTs for epilepsy. Demographic and clinical data were collected from hospital records. Ketogenic dietary therapy response was defined as ≥50% seizure reduction compared to baseline. Many parents had a positive perception of KDTs and were convinced of the necessity of KDTs for their children, although beliefs were wide-ranging. Over half of parents reported concerns about the potential long-term effects of KDTs. Parental beliefs about KDTs were significantly correlated with patient response. This was an attempt to quantify parents' beliefs regarding the use of KDTs for their child's epilepsy. The questionnaire may be used to identify individuals with a less positive attitude towards KDTs and who may be less likely to report a favorable response to KDTs. It is unknown whether people who have positive beliefs about KDTs engage in less nonadherent behavior or whether beliefs regarding KDTs simply reflect outcomes. The evidence behind the long-term side effects of KDTs should be emphasized when counseling patients and their families.

A new potential quality assurance (QA) method is explored (including assessment of depth dose, dose linearity, dose rate linearity and beam profile) for clinical electron beams based on imaging Cerenkov light. The potential of using a standard commercial camera to image Cerenkov light generated from electrons in water for fast QA measurement of a clinical electron beam was explored and compared to ionization chamber measurements. The new method was found to be linear with dose and independent of dose rate (to within 3%). The uncorrected practical range measured in Cerenkov images was found to overestimate the actual value by 3 mm in the worst case. The field size measurements underestimated the dose at the edges by 5% without applying any correction factor. Still, the measured field size could be used to monitor relative changes in the beam profile. Finally, the beam-direction profile measurements were independent of the field size within 2%. A simulation was also performed of the deposited energy and of Cerenkov production in water using GEANT4. Monte Carlo simulation was used to predict the measured light distribution around the water phantom, to reproduce Cerenkov images and to find the relation between deposited energy and Cerenkov production. The camera was modelled as a pinhole camera in GEANT4, to attempt to reproduce Cerenkov images. Simulations of the deposited energy and the Cerenkov light production agreed with each other for a pencil beam of electrons, while for a realistic field size, Cerenkov production in the build-up region overestimated the dose by +8%.

A colour-naming model was developed to categorize volumes for each of the 11 basic names in CIELAB colour space. This was tested with three different sets of data for two languages (English and Mandarin), derived from extensive colour categorization experiments. The performance of the model in predicting colour names was satisfactory, with an average prediction error of 8.3%. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 270–277, 2001

A typical desktop LCD projector was characterised. Having determined the optimum settings of the brightness and contrast controls, measurements were made with a spectroradiometer to establish the additivity of the primaries, inter-channel dependence, colour gamut, tone scale, contrast, spatial non-uniformity, temporal stability and viewing angle variation. Four mathematical models were compared for their accuracy in predicting the colours generated by the display for arbitrary signal inputs. A new model was developed for the S-shaped electro-optical transfer function of the LCD device, and was extended to predict the anomalous colour tracking of the primaries.

In computer graphics, judicious use of colors helps to get the message across. Using several tasks that engage the user in different ways as examples, this tutorial outlines principles for using color effectively in computer graphics. These principles offer a starting point for color choices in the context of user-centered designs. The tutorial provides color selection guidelines based on biological, psychological and technological considerations. Each section ends with a few general guidelines for color selection, summarizing the main points discussed. Prototyping and usability assessment will help you refine and verify your own color choices for each application.

A general framework and first experimental results are presented for a computational model for achieving optimal colour appearance of natural images on television displays. The image quality framework includes: (a) analysis of relationships between overall image quality and quality-related attributes; (b) analysis of relationships between the quality-related attributes and their psychometric correlates; (c) analysis of relationships between the psychometric correlates and the physical parameters of a display; and (d) development of an adaptive algorithm for optimal image appearance by manipulation of the display's parameters. In the psychophysical experiments, observers viewed a series of colour images on high-end consumer television display, to investigate the relationships between overall image quality and four quality-related attributes: brightness rendering, chromatic rendering, visibility of details and overall naturalness. The results of the experiments suggest that these attributes are interrelated. Some subjects can more easily separate the quality-related attributes than other subjects. The overall image quality can be modelled as a linear combination of the brightness rendering and chromatic rendering judgements with different weights, which are subject dependent. The optimal value of the overall image quality judgements is slightly skewed towards the darker end of the lightness scale and towards the more colourful end of the chroma scale. The degree of skewedness depends on image content.

We present simulations and measurements of Cerenkov optical radiation in electron and proton radiotherapy. Photographs of Cerenkov emission from electrons can predict the range to ±1.5mm, but underestimate superficial dose.

3D representations were made of a small Egyptian scarab with a gold band by a number of methods, based on photogrammetry and photometric stereo. They were evaluated for colour fidelity and spatial detail, in the context of a study of toolmarks and manufacturing techniques of jewellery in ancient Egypt. It was found that although a 3D laser scanner gave the best geometric accuracy, the camera-based methods of photogrammetry and photometric stereo gave better representation of fine detail and colour on the object surface.

Media communications involves people communicating with people and encompasses all the diverse forms of theatre, art and literature. Multimedia introduces technology and involves people communi­ cating with people aided by machines; it is more than just individuals interacting with machines. Media communications have evolved in both artistry and engineering prowess over the past century and have attained high levels of sophistication in the familiar media of radio, television, film and print. These provide channels from which information flows from the producers to the receivers, in most cases (apart from telephone) being unidirectional and one-to-many so that the message is literally broadcast through the medium. The use of images for communication can be conveniently classified along two dimensions as shown in Fig. 1. On one axis is the spectrum of applications ranging from pure (art forms) through to applied (graphic design); along the other axis is the flow from provider to consumer. The intermediate electronic forms by which information is conveyed through the channel have until recently been analogue, consisting of AM or PM radio waves, voltages or chemical patterns in silver halide or ink on paper. The revolution that is now gathering pace arises from digital representation of information. By converting the content derived from any medium (be it text, data, audio, graphics, images or video animation) into digital form the way is opened to store, manipulate, transform, transmit and present information in volumes and modalities that have been hitherto only dreamed of. Interactive multimedia (IMM) requires a digital intermediate electronic form to be established for the content. In its current state of development IMM products appear mainly as CD-ROM disks to be played on personal computers but IMM is fast becoming network based, using global data networks that link computer with computer, and thus user with user. In the consumer market personal computers (PCs) with CD-ROM and sound cards for multimedia support are already out-selling non-multimedia PCs by a ratio of nearly 2 : 1. Consumers use these computers primarily for games and education, with a minority for home office and word-processing. Stored data within a typical PC consists mainly of application programmes rather than the user's own data but the capability of extracting and displaying from CD-ROM a mixture of text, sound, graphics, and still and moving images brings a new level of media capability into the home.

Colour management systems rely on the calibration and characterization of colour input and output devices, plus a means of transforming digital images from one device colour space to another. The ICC specification provides a definition for standard device profiles, which will be used by the colour management frameworks developed by Apple, Sun and others within their software operating systems. Further improvements in multimedia colour reproduction will be achieved through better algorithms for gamut mapping and colour appearance.

Multispectral imaging was employed to collect data on the degradation of an 18th century parchment by a series of physical and chemical treatments. Each sample was photographed before and after treatment by a monochrome digital camera with 21 narrow-band filters, with the objective of assessing algorithms for recovery of text from the images. A template-matching technique was used to detect the circular holes in each sample and a four-point projective transform to register the 21 images. Colour accuracy was verified by comparison of reconstructed spectra with measurements by spectrophotometer.

Existing research in colour naming has been mostly focused on a small number of basic colour categories rather than towards the development of more subtle colour identifications. This often leads to an over-saturation in the use of 'basic' colour schemes and can limit the differentiation of new ideas. In this chapter, we present the findings of a free colour naming experiment which has been designed to collect multilingual colour names with their corresponding metric values. The data gathered are being used for the development of a colour naming model that facilitates colour communication within and between different cultures. © 2012 Woodhead Publishing Limited All rights reserved.

This paper describes the methodology and presents preliminary results of a project using multispectral imaging to document the deterioration of parchment. A series of treatments has been applied to degrade samples from a deaccessioned manuscript using both physical and chemical agents. Each sample is photographed before and after the treatment by a multispectral imaging system to record the effect of the treatments on both the writing and the parchment. Here we present the initial imaging of the samples, and we show how some of the agents affect the writing and parchment.

Flexible manufacturing technologies are supporting the routine production of components with freeform surfaces in a wide variety of materials and surface finishes. Such surfaces may be exploited for both aesthetic and performance criteria for a wide range of industries, for example automotive, aircraft, small consumer goods and medial components. In order to ensure conformance between manufactured part and digital design it is necessary to understand, validate and promote best practice of the available measurement technologies. Similar, but currently less quantifiable, measurement requirements also exist in heritage, museum and fine art recording where objects can be individually hand crafted to extremely fine levels of detail. Optical 3D measurement systems designed for close range applications are typified by one or more illumination sources projecting a spot, line or structured light pattern onto a surface or surfaces of interest. Reflections from the projected light are detected in one or more imaging devices and measurements made concerning the location, intensity and optionally colour of the image. Coordinates of locations on the surface may be computed either directly from an understanding of the illumination and imaging geometry or indirectly through analysis of the spatial frequencies of the projected pattern. Regardless of sensing configuration some independent means is necessary to ensure that measurement capability will meet the requirements of a given level of object recording and is consistent for variations in surface properties and structure. As technologies mature, guidelines for best practice are emerging, most prominent at the current time being the German VDI/VDE 2634 and ISO/DIS 10360-8 guidelines. This considers state of the art capabilities for independent validation of optical non-contact measurement systems suited to the close range measurement of table top sized manufactured or crafted objects. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., Videometrics, Range Imaging, and Applications XI, May 25-26, 2011, Munich, Germany, Series: Proceedings of SPIE; no. 8085

3D digital representations of an ancient Egyptian artefact were compared for their rendering of surface detail. Normals were generated by three methods: (1) point clouds from the Arius 3D colour scanner; (2) reflectance transform imaging (RTI); (3) photometric stereo. The latter two were constructed from sets of 64 digital images taken under directional lighting in a hemispherical dome. Analysis of the 3D surface normals of corresponding sections of each object indicated that the photometric stereo method produced the best resolution of spatial detail.

This paper challenges the notion that a fixed spatial resolution is applicable for digitising all items in a collection, irrespective of their characteristics. The fineness of detail in crafted objects depends on the granularity of the substrate, the diameter of the tool, and the visual contrast sensitivity of the craftsman. The ability of an imaging device to capture fine detail is characterised by its modulation transfer function (MTF). A technique based on the 1-D Fourier transform is introduced for determining the spatial frequency of the finest detail in an object. It is proposed that for capturing hand-crafted detail the image should resolve features of 50 µm diameter, requiring 40 samples per mm (1200 dpi).

Two internet-based psychophysical experiments were conducted to investigate the performance of an image sharpness enhancement method, based on adjustment of spatial frequencies in the image according to the contrast sensitivity function and compensation of MTF losses of the display. The method was compared with the widely-used unsharp mask (USM) filter from PhotoShop. The experiment was performed in two locations with different groups of observers: one in the UK, and the second in the USA. Three Apple LCD displays (15" studio, 23" HD cinema and 15" PowerBook) were used at both sites. Observers assessed the sharpness and pleasantness of the displayed images. Analysis of the results led to four major conclusions: (1) Performance of the sharpening methods; (2) Influence of MTF compensation; (3) Image dependency; and (4) Comparison between sharpness perception and preference judgement at both sites.

Colour information is not faithfully maintained by a CCTV imaging chain. Since colour can play an important role in identifying objects it is beneficial to be able to account accurately for changes to colour introduced by components in the chain. With this information it will be possible for law enforcement agencies and others to work back along the imaging chain to extract accurate colour information from CCTV recordings. A typical CCTV system has an imaging chain that may consist of scene, camera, compression, recording media and display. The response of each of these stages to colour scene information was characterised by measuring its response to a known input. The main variables that affect colour within a scene are illumination and the colour, orientation and texture of objects. The effects of illumination on the appearance of colour of a variety of test targets were tested using laboratory-based lighting, street lighting, car headlights and artificial daylight. A range of typical cameras used in CCTV applications, common compression schemes and representative displays were also characterised.

The problem for proper rendering of spatial frequencies in digital imaging applications is to establish the relative contrast sensitivity of observers at suprathreshold contrast levels in typical viewing environments. In an experimental study two methods of evaluating spatial contrast sensitivity were investigated, using targets of graded tonal modulation, at which observers were asked to point to the perceived threshold locations. The results produced by these two methods were rather different from those of the classical methods of vision science, showing a much lower sensitivity over a broader range of spatial frequencies. These may be regarded as complementary to CSF data derived from single- frequency Gabor stimuli and prove to be better suited to the needs of practical imaging applications.

The European collaborative research project IST-2000-28008-VITRA ('Veridical Imaging of Transmissive and Reflective Artefacts') developed an innovative system for high-resolution digital image acquisition for conservation and heritage applications. Using a robotic platform to carry both camera and lighting, it can capture colorimetric images up to 15 metres above floor level, thus eliminating the need for scaffold towers. Potential applications include wall-paintings, tapestries, friezes and stained glass windows in historic buildings such as churches, cathedrals, palaces and monuments. Evaluation of the system was conducted at four sites in Germany and the UK. In the course of the project a number of significant technical innovations were made, including a new panoramic image viewer for the Internet.

The measurement of gloss is conventionally made by specialised instruments that determine the ratio of reflected to incident illumination at a single fixed angle. This study investigated whether digital photography with flash illumination could be used as an alternative. Multiple exposures were combined by a high dynamic range (HDR) imaging technique to produce a two-dimensional intensity profile of the reflectance around the specular point. The method was tested for six paper samples of varying gloss, and the results were found to correlate well with instrumental measurements. The image gloss profiles, however, provided more information about the distribution of the reflection over a range of angles and also gave an indication of the surface texture.

This study investigated four different image sharpness enhancement methods. Two methods applied standard sharpening filters (Sharpen and Sharpen More) in PhotoShop and the other two were based on adjustment of the image power spectrum using the human visual contrast sensitivity function. A psychophysical experiment was conducted with 25 observers, the results of which are presented and discussed. Five conclusions are drawn from this experiment: (1) Performance of the sharpening methods; (2) Image dependence; (3) Influence of two different colour spaces on sharpness manipulation; (4) Correlation between perceived image sharpness and image preference; and (5) Effect of image sharpness enhancement on the image power spectrum.

Experiments were conducted to investigate colour appearance under mesopic vision. Lightness, colourfulness and hue observations of 40 test colours were accumulated for eight phases with four different luminance levels covering 0.1 to 90 cd/m2 and two different stimulus sizes corresponding to viewing angles of 2° and 10° using the magnitude estimation method. The psychophysical effects of luminance level and patch size on colour appearance were investigated and the role of the rods under mesopic vision was explored.

Several approaches have been applied to a digital image of a stained glass window in order to segment the image to match the window's physical structure of separate pieces of glass joined by strips of lead. A three-stage neural network with optimal thresholding strategy gave satisfactory results when followed by a tuned set of Gabor filters.

Two sets of color appearance data were accumulated for investigating the difference between LCD projector and LCD self-luminous colors. Psychophysical experiments were conducted using magnitude estimation methods. These colors were viewed against different neutral backgrounds. These data sets were used to test the performance of five color appearance models (CIECAM97s, Hunt94, LLAB, RLAB and CIELAB together with two most recently proposed revisions of CIECAM97s: Fairchild and FC).

This paper describes the characterization of cine film, by identifying the relationship between the Status A density values of positive print film and the XYZ values of conventional colorimetry. Several approaches are tried including least-squares modeling, tetrahedral interpolation, and distance weighted interpolation. The distance weighted technique has been improved by the use of the Mahalanobis distance metric in order to perform the interpolation, and this is presented as an innovation.

A psychophysical experiment was conducted to investigate the relationship between sharpness and preferred color of images displayed on a CRT monitor screen. Blurred versions of each of four original images were generated by convolution with a low-pass Gaussian filter. Sharpened versions of these images were created through adjustment of the image power spectrum. Each test image was decomposed into a set of spatial frequency bands, defined as octaves of the pixel sampling frequency. The Fourier power spectrum was derived, then amplitudes of selected bands were adjusted to enhance the desired spatial frequencies. The experimental results indicated that: (1) sharpness was perceived to be increased when certain spatial frequency bands were enhanced; (2) weighting the frequency bands using the standard observer's contrast sensitivity function (CSF) gives better results for particular distances; and (3) preferred image color is strongly related to image sharpness.

Visual communication is a key aspect of human-computer interaction, which contributes to the satisfaction of user and application needs. For effective design of presentations on computer displays, color should be used in conjunction with the other visual variables. The general needs of graphic user interfaces are discussed, followed by five specific tasks with differing criteria for display color specification - advertising, text, information, visualization and imaging.

In this study, the characterization method for a typical desktop LCD color projector is reviewed. Measurements were made with a spectroradiometer to establish the additivity of the primaries, inter-channel dependence, color gamut, tone scale, contrast, spatial non-uniformity, temporal stability and viewing angle variation. In the case of tone characterization, LCD projectors show S-shaped curve between input digital values and output luminance unlike the conventional CRT monitor represented by a power function. Mathematical models to predict the S-shaped electro-optical transfer function have been empirically derive.d Four mathematical models including PLCC, GOG, S-Curve Model I and II were compared for their accuracy in predicting the colors generated by the display for arbitrary signal inputs. It is proven that the newly derived S-Curve Model I and II work successfully for an LCD projector.

A general framework and first experimental results are presented for the `OPTimal IMage Appearance' (OPTIMA) project, which aims to develop a computational model for achieving optimal color appearance of natural images on adaptive CRT television displays. To achieve this goal we considered the perceptual constraints determining quality of displayed images and how they could be quantified. The practical value of the notion of optimal image appearance was translated from the high level of the perceptual constraints into a method for setting the display's parameters at the physical level. In general, the whole framework of quality determination includes: (1) evaluation of perceived quality; (2) evaluation of the individual perceptual attributes; and (3) correlation between the physical measurements, psychometric parameters and the subjective responses. We performed a series of psychophysical experiments, with observers viewing a series of color images on a high-end consumer television display, to investigate the relationships between Overall Image Quality and four quality-related attributes: Brightness Rendering, Chromatic Rendering, Visibility of Details and Overall Naturalness. The results of the experiments presented in this paper suggest that these attributes are highly inter-correlated.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Display color can be represented by a simple two-stage model, although the display performance is affected by aging, magnetic field sand various other factors. For optimum image rendering there should be a close match between the source and destination devices, in terms of primary chromaticities, white point, gamma, palette encoding and gamut mapping. Characterization procedures for displays include visual assessment, visual matching and measurement with a tricolorimeter or telespectroradiometer. Color may be communicated in images either by encoding the image directly in a standard color space, or by attaching a profile that allows the data values to be interpreted. Color correction of Internet images may be carried out on either the receiver side or on the server side. Evaluation of the effectiveness of color Internet image delivery should include repeatability and consistency of the display characterization procedure, color accuracy of the imagery and general usability considerations.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Digital color imaging has developed over the past twenty years from specialized scientific applications into the mainstream of computing. In addition to the phenomenal growth of computer processing power and storage capacity, great advances have been made in the capabilities and cost-effectiveness of color imaging peripherals. The majority of imaging applications, including the graphic arts, video and film have made the transition from analogue to digital production methods. Digital convergence of computing, communications and television now heralds new possibilities for multimedia publishing and mobile lifestyles. Color engineering, the application of color science to the design of imaging products, is an emerging discipline that poses exciting challenges to the international color imaging community for training, research and standards.

Digital photography was applied to the capture of images of the stained glass windows in the historic parish church in Fairford, Gloucestershire, England. Because of their size, the windows had to be photographed in 45 separate sections in order to capture all the detail present in the painting on the glass. The digital images of each section, approximately 3000 by 2300 pixels, were then mosaiced together in order to construct the very high resolution image needed for the complete window. A special backlight panel was constructed for the purpose, and techniques developed for minimizing the effects of reflected light and for calibrating the color of the images. Improvements in the technology for mounting and positioning the camera were identified as the most significant factors currently preventing the widespread adoption of this technology for virtual heritage applications.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The researcher was the chief editor of this book which analyses the problems of device-independent reproduction of colour, especially in photo-realistic colour images, and outlines the different solutions available. Particular attention is paid to the capabilities of the human visual system, the characterisation of colour imaging devices, and the state of the art in commercial colour management systems. It summarises research findings and presents new scholarly insights into the evolution and capabilities of colour management systems. Since 1990 there has been a phenomenal growth in colour imaging facilities for desktop computers. This has been evident not only in colour monitors and graphic user interfaces, but also in peripheral devices such as colour ink-jet printers and digital cameras. The ability to store and access digital colour images was greatly enhanced through the availability of CD-ROM drives and Internet connections in all new PCs. The problem for users and system developers alike is how to achieve good quality image reproduction, with controllable, repeatable and consistent colour across a wide range of input and output devices. How do viewing conditions affect the appearance of colour on a print or on a display? How can someone purchasing an item from an on-line catalogue, for example, be sure that the colour will be correct? The book charts the new discipline known as 'Colour Engineering', applying the principles of colour science to the practical problems of developing colour imaging products and reproducing colour images. It was targeted at both practitioners and students of colour management in digital imaging systems. It was written by leading experts in the field, based in the UK, Europe and USA. It was co-published by John Wiley and the Society for Information Display (SID) in their series on the state of the art display technology.

Two newly derived characterization models for a liquid-crystal (LC) display have been tested for five LC-based displays. Data measured from a series of test colors indicated that all LC-based displays showed similar characteristics, including an S-shaped tone curve and poor channel chromaticity constancy. Because they include a hyperbolic function in their definition, the models do not have analytical inverses, and so iterative mathematical techniques are applied. It was shown that a new characterization model based on a hyperbolic function fits the tone curve very accurately with only four coefficients per channel for any type of LCD. In addition, it was also shown that the first derivative of the function provides a means of accurate correction of the chromaticity variation.