Color Consistency Research Articles

Triple U-net: Hematoxylin-aware nuclei segmentation with progressive dense feature aggregation.

Nuclei segmentation is a vital step for pathological cancer research. It is still an open problem due to some difficulties, such as color inconsistency introduced by non-uniform manual operations, blurry tumor nucleus boundaries and overlapping tumor cells. In this paper, we aim to leverage the unique optical characteristic of H&E staining images that hematoxylin always stains cell nuclei blue, and eosin always stains the extracellular matrix and cytoplasm pink. Therefore, we extract the Hematoxylin component from RGB images by Beer-Lambert's Law. According to the optical attribute, the extracted Hematoxylin component is robust to color inconsistency. With the Hematoxylin component, we propose a Hematoxylin-aware CNN model for nuclei segmentation without the necessity of color normalization. Our proposed network is formulated as a Triple U-net structure which includes an RGB branch, a Hematoxylin branch and a Segmentation branch. Then we propose a novel feature aggregation strategy to allow the network to fuse features progressively and to learn better feature representations from different branches. Extensive experiments are performed to qualitatively and quantitatively evaluate the effectiveness of our proposed method. In the meanwhile, it outperforms state-of-the-art methods on three different nuclei segmentation datasets.

Revisit Retinex Theory: Towards a Lightness-Aware Restorer for Underexposed Images

We investigate how to correct exposure of underexposed images. The bottleneck of previous methods mainly lies in their naturalness and robustness when dealing with images with various exposure levels. When facing well-exposed or extremely underexposed images, they may produce over- or underenhanced outputs. In this paper, we propose a novel retinex-based approach, namely, LiAR (short for lightness-aware restorer). The word “lightness-aware” refers to that the estimated illumination not only is a component to be adjusted but also serves as a measure that reflects the brightness of the scene, determining the degree of adjustment. In this way, underexposed images can be restored adaptively according to their own brightness. Given an image, LiAR first estimates its illumination map using a specially designed loss function which can ensure the result’s color consistency and texture richness. Then adaptive correction is performed to get properly exposed output. LiAR is based on internal optimization of the single test image and does not need any prior training, implying that it can adapt itself to different settings per image. Additionally, LiAR can be easily extended to the video case due to its simplicity and stability. Experiments demonstrate that facing images/videos with various exposure levels, LiAR can achieve robust and real-time correction with high contrast and naturalness. The relevant code and collected data are publicly available at https://cslinzhang.github.io/LiAR-Homepage/.

Gonad development in mature females of tidal spray crab Plagusia depressa (Brachyura: Plagusiidae)

AbstractInformation on crustacean ovary development is important to properly understand many life story traits. This study aimed to describe macroscopic and microscopic stages of gonad development in females of Plagusia depressa (Fabricius, 1775). Thirty females of P. depressa were captured manually and underwent analgesia by decreasing temperature to collect the gonads, which underwent standard histological techniques. The macroscopic and microscopic appearance of the ovaries and the frequency of germ cells and their location in the organ were used to determine the stage of gonadal development. A total of four stages were defined. Stage 1: marks the end and beginning of gonadal maturation cycle. The germinal zone is tightly reduced with few oogonia and pre‐vitellogenic oocytes are rarely observed. Stage 2: yellow to orange colour and firm consistency. Oogonias and pre‐vitellogenic oocytes can be observed at this stage, as well as a few vitellogenic oocytes at organ limits. Stage 3: colour between red and dark brown. The gonad already presents many mature oocytes. Stage 4: characterized by the abundance of mature oocytes that occupy almost the entire organ. Macroscopic appearance of the female reproductive system, cell characteristics and changes during maturation of P. depressa corroborate with the normally found in Malacostraca.

Image real-time augmented reality technology based on spatial color and depth consistency

Augmented reality can enhance people’s perception of the environment by embedding virtual objects or other information in real-time images. In this paper, the color image is used as a reference to calculate the confidence of the original depth map, and stereo matching is performed according to the feature points. The depth map is mainly enhanced by the color, edge, and segmentation results of the color image. A deep computing system based on augmented reality is designed. The system can use a binocular camera to collect object images in real time and obtain better parallax images by correcting the calibrated image. The semi-global block matching algorithm and depth calculation are used to realize the tracking registration of virtual objects. Experiments in different environments show that the system has good real-time performance, light invariance, and depth consistency.

Color consistency in the appearance of bleached fabrics.

Human observers are remarkably good at perceiving constant object color across illumination changes. However, there are numerous other factors that can modulate surface appearance, such as aging, bleaching, staining, or soaking. Despite this, we are often able to identify material properties across such transformations. Little is known about how and to what extent we can compensate for the accompanying color transformations. Here we investigated whether humans could reproduce the original color of bleached fabrics. We treated 12 different fabric samples with a commercial bleaching product. Bleaching increased luminance and decreased saturation. We presented photographs of the original and bleached samples on a computer screen and asked observers to match the fabric colors to an adjustable matching disk. Different groups of observers produced matches for original and bleached samples. One group of observers were instructed to match the color of the bleached samples as they were before bleaching (i.e., compensate for the effects of bleaching); another, to accurately match color appearance. Observers did compensate significantly for the effects of bleaching when instructed to do so, but not in the appearance match condition. Results of a second experiment suggest that observers achieve color consistency, at least in part, through a strategy based on local spatial differences within the bleached samples. According to the results of a third experiment, these local spatial differences are likely to be the perceptual image cues that allow participants to determine whether a sample is bleached. When the effect of bleaching was limited or uniformly distributed across a sample's surface, observers were uncertain about the bleaching magnitude and seemed to apply cognitive strategies to achieve color consistency.

A Color Consistency Processing Method for HY-1C Images of Antarctica

The HY-1C satellite, as part of China’s optical satellite constellation for global ocean monitoring, monitors the ocean and coastal environment by the three broad visible bands of the Coastal Zone Imager (CZI) instrument. However, as a result of the sensor instrument noise, the atmospheric environment during imaging, and the shooting angle, the satellite images often show uneven illumination and inconsistent color between neighboring images. In this paper, according to the characteristics of the HY-1C CZI instrument, we propose a color consistency processing framework for coastal zone images of Antarctica. First of all, the high-frequency and low-frequency information of the image is separated by a statistical filter with simple clustering. The uneven lighting is then replaced by artificial lighting, which is globally uniform. Finally, the color difference between images is corrected by a color transfer method. In order to evaluate the color consistency results quantitatively, a new quantitative evaluation method is proposed. The experimental results for the coastal zone images of Antarctica show that the new processing framework can effectively eliminate the unevenness in the lighting and color. The mosaic results show a good performance in consistent lighting and tones, and the lack of visible mosaic lines proves the effectiveness of the proposed method. The quantitative evaluation analysis confirms the superiority of the proposed method over the Wallis method.

Color Difference Optimization Method for Multi-source Remote Sensing Image Processing

This paper proposes an approach to solve the problem of color inconsistency after the fusion and splicing of multi-spectral images of multi-source domestic satellites, by using regularly division the high-resolution remote sensing images, block by block computing the multiple linear regression and percent clip stretch. First of all, the remote sensing image is divided into blocks and multiple linear regression is carried out separately in each block. Secondly, on the basis of the image to be corrected after regression, percentage truncation and stretching are carried out on the over-concentrated gray band, so that the gray histogram distribution of the gray band is similar to that of the reference image. This scheme ensures that all pixels participate in the calculation, which not only improves the accuracy of the model, but also avoids the problems of long processing time and memory overflow caused by the large amount of high-resolution remote sensing image data. At the same time, each scene image selects an appropriate truncation percentage according to the evaluation index to solve the problem of excessive color difference caused by too concentrated image band gray. The experimental results show that the scheme in this paper can effectively solve the problems of too large color difference and too concentrated gray scale in image band. Compared with traditional methods, it has better performance in model accuracy, color retention and time efficiency.

Digital Textile Printing: A New Alternative to Short-Run Textile Printing in Ghana

This paper is a part of a broader research into textile design technology and trends across the world and their reflection on the local Ghanaian textile industry. It places conventional manual screen printing and digital textile printing technologies side by side and discusses the various drawbacks of screen printing as against the advantages of digital textile printing to illustrate a path for a wider consideration of the latter in Ghanaian small to medium scale textile production. Short-run textile printing commissions are the main source of jobs for small to medium scale textile producers in Ghana. And manual screen printing is the main process employed by these small-scale textile printers. However, screen printing has various layers of limitations such as poor registration of the design, stains, pinholes, colour correctness, colour consistency, colour smear, dye migration, scorching, improper curing, amongst others. These layers of limitations negatively affect the overall outcome of the prints. So, as it stands now, short-run textile printing commissions are either produced manually, of course, with several inconsistencies or outsourced to China and other countries at a higher production cost. This is because, the large-scale textile factories in Ghana could print a minimum of 2400 yards due to their machine settings, calibration and running cost to make the least returns. This study highlights some of the milestones in the development of digital textiles print machines and examines some of the key aspects of their tremendous production aptitudes for short-run textile commissions. The case study research method is used because data comes largely from documentation, archival records, interviews and physical artefacts.
 Keywords: Textile Design, Digital Textile Printing, Screen Printing, Short-run Prints.

Optical and Chromaticity Properties of Metal-Dielectric Composite-Based Multilayer Thin-Film Structures Prepared by RF Magnetron Sputtering

Coated glass products, and especially the low-emissivity coatings, have become a common building material used in modern architectural projects. More recently, these material systems became common in specialized glazing systems featuring solar energy harvesting. Apart from achieving the stability of optical parameters in multilayer coatings, it is also important to have improved control over the design of visual color properties of the coated glass. We prepare metal-dielectric composite (MDC)-based multilayer thin-film structures using the radio frequency (RF)-magnetron sputtering deposition and report on their optical and chromaticity properties in comparison with these obtained using pure metal-based Dielectric/Metal/Dielectric (DMD) trilayer structures of similar compositions. Experimentally achieved Hunter L, a, b values of MDC-based multilayer building blocks of coatings provide a new outlook on the engineering of future-generation optical coatings with better color consistency and developing approaches to broaden the range of achievable color coordinates and better environmental stability.

New Color Rendering Metrics

Color is not a physical properly of object, but rather a human perception enabled by light. Never­theless the color of light sources is described by the industry primarily in terms of two metrics, correlated color temperature (CCT) and color rendering index (CRI), that are only indirectly related to human perception. CCT is intended to characterize the appearance of the illumination generated by source, and CRI is intended to characterize the appearance of objects illuminated be the source. There two color metrics developed nearly of half-century ago, are increasingly being challenged because new source are being developed with increasingly exotic spectral power distribution.
 The new color metric applicable to the color appearance of the light emitted by at light source and quantified by the CCT and D.
 The chromaticity is one of the critical parameters for light sources for general lighting and normally specified with chromaticity coordinates CIE (x, y) or (', '). However these two numbers do not provide the color information intuitively. For practical purposes, collated color temperature (CCT) is commonly used to provide the chromaticity information of general illumination source CCT, however, provides only one dimension of the chromaticity and there is ano­ther dimension, which is the position of chromati­city with respect to Plancian locus. For this purpose «D» or similar terms as distance from Plancian locus have been need used in some part at the industry but these had not beer officially defined is any standard.
 Color rendering is general term for describing the ability of a light source to provide color information to human observer when objects are illuminated by that source like CCT color rendering index (CRI), the most accepted measure of color rendering.
 CRI was developed, through the system of colori­metry, simply to be an indication of how «natural» or «undistorted» the light source makes the color of objects appear when illuminated by the source when used as the sole measure of color rendering for a light source, CRI simply cannot meet expectations. With the advent of SSL, these limitations have become more widely recognized.
 It was proposed a two-metric system combi­ning CRI, a measure of color consistency with respect to a reference source, with gamut area index (GAI), a measure of color saturation. When used to ga­ther, the two metrics appear to optimize the color appeara­nce of natural objects like fruits and vegetable enhancing their vividness with making them appear unnatural.
 CCT is shown in commercial instruments but D is often avai­lable. D needs to be calculated using the method of triangular solution:
 
 Create a table CCT is distance di to Plancian locus on () coordinate;
 Find the closest point in the table;
 Solve the triangle for the neighboring 2 points.
 
 Gamut area of light source is commonly calculated as the area of the polygon defined by the chromaticities in CIE 1977 (', ') color space of the light CIE TCSs. Gamut area of EES is sealed to 100 and defined as gamut area index. The gamut area of any other light source is scaled accondingle.

Relationship of antiepileptic drugs to generic brittleness in patients with epilepsy

PurposeThe purpose of the study was to assess if any antiepileptic drug (AED) was associated with patients being generic brittle (GB) and if any specific AED caused – and was not merely associated with – more frequent switch problems. MethodsChi square and binary logistical regression analysis were performed, using a previously described study in patients with epilepsy who were routinely followed at the University of Maryland epilepsy outpatient clinic in Baltimore, Maryland. Determination of generic brittleness mirrored clinical practice and included patient opinion about generic formulations, usually based on a history of worsened seizures or side effects with prior AED formulation switching. The dataset included a total of 148 patients, who took 30 different AED formulations. Patients collectively took 530 AED formulation products. ResultsTaking lamotrigine immediate release (IR) tablets was associated with a greater probability of being GB and tended to cause more frequent switch problems. Interestingly, six AEDs – Vimpat tablet, carbamazepine IR tablet, phenobarbital (any formulation), gabapentin capsule, Lyrica capsules, and phenytoin (any formulation) – were associated with a reduced probability of being GB, although perhaps not through greater efficacy and tolerability, or better formulation quality. Since tablet and capsule appearance may influence patient perceptions and clinical outcomes, it was observed that the six AEDs less associated with being GB also tended to have fewer generics, and hence possibly lessen treatment uncertainties from the patient perspective. A patient taking more AEDs had significantly increased odds of having a switch problem. An additional observation was that, when a generic was available for their most problematic AED, GB patients took a generic AED only 50% of the time, while not GB patients took a generic AED all the time. ConclusionsTaking lamotrigine IR tablets was associated with a greater probability of being GB and tended to cause more frequent switch problems than other AEDs in this cohort of patients. Six AEDs were associated with a reduced probability of being GB. The lower number of different generics for these six drugs may result in greater patient certainty in medication identity, due to greater consistency in medication color, shape, and size, and hence less generic skepticism or generic brittleness. Also, patients taking more AEDs showed increased odds of a switch problem.

Individual Variation in Semen Characteristics of Murrah Buffalo Bulls

This study evaluated the variation in semen characteristics between two individual Murrah buffalo bulls. Two hundred and ninety semen samples were involved in this study. The results showed that most of the semen had a milky white color with moderate consistency. The Bull B1 tended to have higher proportion of creamy color and moderate consistency than the Bull B2. The ejaculatory volume is varied (P<0.01) between Bull B1 and Bull B2. However, semen pH and sperm concentration of Bull B1 and B2 were equal (P>0.05). The individual bull had a highly significant effect (P<0.01) on sperm motility of fresh semen. The individual variation (P<0.05) also found on sperm motility of before freezing. Whereas, sperm motility of post-thawing semen and recovery rate value were not significantly influenced (P>0.05). Moreover, it was found that the frozen semen production differed (P<0.01) between two individual bulls, with bull B1 had higher production than the bull B2. This study clearly demonstrates that the frozen semen production of Murrah buffalo is highly dependent on the individual bull. However, the variation in frozen semen production between two bulls studied here is still qualified to be used for artificial insemination.

Nasal and Laryngeal Rhinosporidiosis in Horses Treated with Electrocautery

Background: Rhinosporidiosis is considered an endemic disease in some countries and can affect several species of animals, among them, also equines. In this specie, although the nasal cavity is the most common site of infection, in some cases, it could also be spotted in the larynx region. The present study had as an objective to describe two cases of rhinosporidiosis in horses, one of them nasal and the other in the laryngeal area.Cases: Horse 1. A 12-year-old male Standardbred was sent to the veterinary hospital for the resection of the formation presented in the mucocutaneous junction of the left nostril. During the physical exam, a red mass of a moderately consistency, with an irregular, verrucous, pedunculated and ulcerated surface was observed, measuring approximately 2 centimeters in diameter. The surgical procedure for the resection of the mass was done through the use of the electrocautery technique, with the animal sedated with a romifidine dose of 0.08 mg/kg, a butorphanol dose of 0.04 mg/kg and a local anesthesia of 2% lidocaine. Eight months after the surgical procedure, the animal returned to the hospital and the presence of three new masses was noted in the same nostril, around the region where the extracted mass used to be found and they resembled the previous lesions. The horse’s owner didn’t authorize a new surgery or a new histopathological exam of the lesions. Horse 2. The other case refers to an asymptomatic 15-year-old male mixed breed. During a routine gastroscopic exam, the presence of several reddish coloration nodular and polypoid formations of irregular surface was observed in the larynx. Only one formation in the dorsal portion of the pharynx was observed. During the macroscopic exam, it was observed heterogeneously formation with a grayish-white color and soft consistency aspect. The surgical procedure for the resection of the mass, also through electrocautery, was performed with the animal, previously sedated with a detomidine dose of 0.01 mg/kg and a butorphanol dose of 0.02 mg/kg through intravenous. The contact plate of the electrocautery was fixed to the left side of the animal's neck. After the introduction of the endoscope through the nostril and advancing to the pharynx and larynx, lidocaine 2% without a vasoconstrictor was sprayed in the region. The polyps were individually wrapped by the polypectomy loop, passed through the endoscope operational channel and, at this time, the electrocautery was activated. After the treatment, periodical return appointments were made for the next two months. During the fourth appointment, the animal presented, in the endoscopy, a relapse of a few formations which were, again, removed with electrocautery. The histopathological exam in both cases was characterized by the presence of sporangia that was distributed homogeneously across the submucosal blade interspersed with mild to moderate mixed inflammatory infiltration composed predominantly of lymphoplasmic cells, followed by neutrophils and macrophages, as well as some hemorrhage area and the presence of macrophages with hemosiderin. These histopathological findings were consistent with rhinosporidiosis.Discussion: Rhinosporidiosis in horses, although rare, must be considered not only in cases of nasal formations, their most common form, but also in laryngeal cases, while the use of electrocautery is an efficient technique in the removal of the lesions, allowing for a good tissue healing and no postoperative complications. Nevertheless, follow-ups after treatment is always recommended to identify possible relapses.

Improved color attenuation prior based image de-fogging technique

Single image de-fogging has been a confronting problem due to its ill-posed nature. In this paper, a de-fogging technique based upon color attenuation prior (CAP) has been proposed. CAP uses linear model and learning the parameters of this model with a supervised learning method for estimating the scene depth of a foggy image. This depth map is utilized for transmission map estimation. Transmission (t) is one of the important parameter of physical model based de-fogging techniques which describes the portion of the light coming from the scene point that is not scattered and reaches the camera. It is a map called transmission or transparency of the fog 0 < t(x) < 1, t(x) = 0 means completely foggy, t(x) = 1 means fog-free. The more accurately the transmission or depth is estimated, the better the defogging performance will be. In the proposed work, to quickly and accurately estimate the transmission map, a sub-sampling based local minimum operation and fast gradient domain guided image filtering (GDGF) is applied on CAP based initial depth map. The edge attentive restraints of GDGF make edges to be conserved better in the de-fogged images. The de-fogged images obtained by CAP technique suffer from dullness and higher illumination variations due to consideration of fog image degradation model in homogeneous environment and a constant value of atmospheric light. Such variations are removed in the proposed work by using Lambert’s law of illumination reflection, which helps to compensate non uniform illumination, causes simultaneous dynamic range modification, color consistency, and lightness rendition without producing the artifacts in a de-fogged image. To improve the processing speed, image sub-sampling mechanism is used in various steps of image de-fogging. The sub-sampling is used in such a way that the quality of the output at any step is not compromised as demonstrated through various quality parameters. Experimental results show that the proposed approach outperforms state-of-the-art fog removal techniques in terms of efficiency and the de-fogging effect.

Semi-Supervised Texture Filtering With Shallow to Deep Understanding

This work proposed a semi-supervised method for automatic texture filtering. Our method leveraged a limited amount of labeled data and a large amount of unlabeled data to train Generative Adversarial Networks (GANs). Separate loss functions were designed for both labeled and unlabeled datasets. Our main contribution is the introduction of knowledge extracted from shallow and deep layers in neural networks. Loss defined within shallow layers preserves the edge, while loss defined within the deep layers identifies the semantic content and conversely removes the small-scale texture variations. This contribution directly addresses the major challenge for texture filtering, distinguishing the structural content from non-structural textures at the pixel level. The extracted information, in our study, improved the content and color consistency before and after the process of filtering, for unlabeled samples in particular. The proposed method offers twofold benefits: first, significant reductions in the amounts of time and effort expended in reconstructing the labeled dataset, especially given the delicate operations required at the pixel level; second, a reduction in over-fitting, in supervised learning with a small amount of labeled data, by utilizing a large amount of unlabeled data. The results confirm that our method can perform comparably with non-learning-based methods, alleviating the demand for the determination of optimal parameter values.

A comparative study of the clinical andhistopathological features of normal labial mucosa and redundant tissue in double lip

Introduction: double lip is one of lip abnormalities that may be congenital or acquired. It consists of a fold of excess tissue on the mucosal side of the lip. It causes functional and aesthetic problems to affected patientsAim of the work : The present study was performed to compare clinically and histopathologically between redundant tissue in double lip and normal labial mucosa.Subjects and methods: Seventeen patients with congenital non syndromic double lip were selected. Redundant tissues were removed surgically together with part of adjacent normal mucosa as part of the surgical manipulation. Hematoxylin and eosin staining was done to compare both tissues microscopically. Expression of ki-67 and p53 was evaluated in both tissue by immunohistochemistryResults: Clinically, redundant tissue appeared as thick extra fold with normal mucosal color and soft consistency analogous to normal labial mucosa. This redundant tissue was removed surgically without any complications. Histopathologically, normal labial mucosa revealed non keratinized stratified squamous epithelium and delicate underlying connective tissue. Excess tissue exhibited parakeratosis, acanthosis, elongation of rete pegs. The underlying connective tissue was fibrotic with inflammatory cell infiltration. In normal labial mucosa, ki-67 was detected only in parabasal layer of epithelium whereas it was localized in parabasal and superficial layers of epithelium in redundant tissue. No expression of p53 was detected in both normal and excess tissue. For both ki-67 and p53, the difference in expression between normal and redundant tissue was significant.Conclusion : Redundant tissue is a benign hyperplastic tissue that require surgical removal. So surgical excision here is the treatment of choice when excess tissue causes functional and aesthetic problems. Moreover, the high proliferation of redundant tissue may necessitate the surgical excision of this tissue.

IGG-MBS: Iterative Guided-Gaussian Multi-Baseline Stereo Matching

This paper presents an improved dense disparity estimating technique for a collection of multi-baseline stereo (referred to as MBS in the text) images. The flow of the proposed system consists of two main frameworks: a preliminary cost calculation and initial disparity estimating framework, and an iterative cost refinement framework. The first framework implements an accurate multi-baseline stereo cost (referred to as MBSC in the text) calculation method, and a scan line optimization inspired by the Semi Global Matching (SGM) algorithm. Cost volumes of each two-view camera pair are calculated by fusing two pixel dissimilarity measures: i) weighted Census transformation and ii) sum of absolute difference color consistency term (SAD-Census). The initial disparity map between reference and the matching view with the largest baseline displacement is calculated by summing-and-interpolating SAD-Census costs of the current and all neighboring camera pairs in-between, and taking the minimum after aggregating for sixteen directions. The second framework refines the aggregated MBSC volume recursively. In each iteration, individual pair-wise disparity maps are used to warp matching views towards the reference to create binary masks that resemble overlapping differences. White locations in the mask represent incorrect correspondence matches, thus a penalty is added for costs associated with, adapting a Gaussian modulating function. This significantly reduces the selection probability of incorrect disparity minima in proceeding iterations. A Guided filter-based Rolling Guidance filter is applied to further up-vote the probability of pixels with the lowest costs, which are similar or close enough to ground truth readings. Through experimental results evaluated on the Middlebury dataset, we show that our method leads to effective and efficient multi-baseline disparity estimations.

Colour Consistency in Print: Ghanaian Printers’ Knowledge and Awareness of Colour Management

With the advances print industry, high-quality printout is crucial for the survival of any press house as the creation and retention of loyal customers greatly depend on it. However, the ability to consistently print high-quality materials is one of the greatest challenges in the printing industry over the years due to differences and limitations in various imaging devices as well as software used in colour reproduction workflows. Colour Management system has proven to be the surest way to achieve consistent colour reproductions. However, understanding how devices capture and reproduce colour, as well as, ensuring an accurate, predictable and consistent reproduction of colour requires a change in workflow and efficient utilisation of digital technologies available. In spite of the use of colour management system and available print technologies the ability to print consistent high-quality colour reproduction repeatedly still remains a great challenge for less endowed press houses all over the world. This study employed the survey research design making use of questionnaires and observation to ascertain the awareness and knowledge levels of print technicians on colour management issues in selected print houses in Ghana. The findings revealed that many of the presses have the required imaging devices yet not calibrated, environmental conditions required for effective calibration were not strictly adhered to and there is low level of awareness on the use of colour management system. The study concludes that the sampled press houses still have fair knowledge about effective colour management practices and the use of available print technologies that help presses to consistently produce high-quality prints. The researchers, therefore, recommend that the presses adhere to effective colour management practices and also employ the available print technologies to help improve their colour output consistency and quality to stay competitive.

Depth Estimation From Light Field Using Graph-Based Structure-Aware Analysis

Existing light field depth map estimation approaches only utilize partial angular views in occlusion areas and local spatial dependencies in the optimization. This paper proposes a novel two-stage light field depth estimation method via graph spectral analysis to exploit the complete correlations and dependencies within angular patches and spatial images. The initial depth map estimation leverages the undirected graph to jointly consider occluded and unoccluded views within each angular patch. The estimated depth minimizes the structural incoherence of its corresponding angular patch with the focused one by evaluating the highest graph frequency component. Subsequently, depth map refinement optimizes the initial depth map with the color consistency and smoothness formulated by weighted adjacency matrix. The structural constraints are efficiently employed using low-pass graph filtering with Chebyshev polynomial approximation. Experimental results demonstrate that the proposed method improves the depth map estimation, especially in the edge regions.

Automatic Registration of Multi-Projector Based on Coded Structured Light

Multi-projector display systems are widely used in virtual reality, flight simulators, and other entertainment systems. Geometric distortion and color inconsistency are two key problems to be solved. In this paper a geometric correction principle is theoretically demonstrated and a consistency principle of geometric correction is first proposed. A new method of automatic registration of a multi-projector on a curved screen is put forward. Two pairs of binocular-cameras are used to reconstruct the curved screen. To capture feature points of the curved screen precisely, a group of red-blue coded structured light images is designed to be projected onto the screen. Geometric homography between each projector and the curved screen is calculated to gain a pre-warp template. Work which can gain a seamless display is illustrated by a six-projector system on the curved screen.