2,267 research outputs found
Digital Color Imaging
This paper surveys current technology and research in the area of digital
color imaging. In order to establish the background and lay down terminology,
fundamental concepts of color perception and measurement are first presented
us-ing vector-space notation and terminology. Present-day color recording and
reproduction systems are reviewed along with the common mathematical models
used for representing these devices. Algorithms for processing color images for
display and communication are surveyed, and a forecast of research trends is
attempted. An extensive bibliography is provided
Engineering data compendium. Human perception and performance. User's guide
The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use
Quantifying the colour appearance of displays.
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Quantification of metamerism and colour constancy
Reliable colour constancy
by industry for colour
conducted to quantify
metamerism.
and metamerism indices are highly desired
quality control. Two experiments were
the degree of colour constancy and
In the colour constancy experiment, 240 wool samples were
prepared and scaled using a magnitude estimation method by a
panel of 5 experienced observers under sources D65, A and TL84. 2
corresponding data sets derived from the experimental results were
used to test various chromatic adaptation transforms. The results
clearly show that the BFD transform gave the most precise prediction
than the other transforms. Attempts were also made to derive 4 new
transforms from four independent data sets. These gave similar
performance as that of the BFD, but overcome the BFO's problem
(incapable of predicting some of the high saturated colours). Hence,
these transforms should be used with confidence for predicting the
degree of colour constancy.
This experimental results were also used to test various
uniform colour spaces and colour appearance models. The Hunt94
model gave the most precise prediction to the colourfulness and hue
results. Modification was made to its lightness scale for improving
the fit.
In the metamerism experiment, 76 pairs of wool samples were
prepared and assessed with 20 observations using a grey scale under
7 sources: D65, A, TL84, TL83, P27, W and WW. The experimental
results were used to test 3 types of illuminant metamerism indices
derived here. It was found that calculating colour difference using 3
colour difference formulae, i.e. CMC, BFD and CIE94 gave the most
precise prediction to the visual results. The degree of precision is
quite satisfactory in comparison with typical observer precision.
A new standard deviate observer (SDO) was also derived. This
together with the CIE SDO and 1964 Observer were tested using the
author's and the Obande's data. The results showed that the new SDO
predicted results more accurate than those from the other two CIE
Observers. An Observer Metamerism Index (OMI) was also derived
to indicate the degree of metamerism based upon the new SDO. The
results showed that the new SDO was more suitable for indicating the
degree of observer metamerism
Evaluation and improvement of the workflow of digital imaging of fine art reproduction in museums
Fine arts refer to a broad spectrum of art formats, ie~painting, calligraphy, photography, architecture, and so forth. Fine art reproductions are to create surrogates of the original artwork that are able to faithfully deliver the aesthetics and feelings of the original. Traditionally, reproductions of fine art are made in the form of catalogs, postcards or books by museums, libraries, archives, and so on (hereafter called museums for simplicity). With the widespread adoption of digital archiving in museums, more and more artwork is reproduced to be viewed on a display. For example, artwork collections are made available through museum websites and Google Art Project for art lovers to view on their own displays. In the thesis, we study the fine art reproduction of paintings in the form of soft copy viewed on displays by answering four questions: (1) what is the impact of the viewing condition and original on image quality evaluation? (2) can image quality be improved by avoiding visual editing in current workflows of fine art reproduction? (3) can lightweight spectral imaging be used for fine art reproduction? and (4) what is the performance of spectral reproductions compared with reproductions by current workflows? We started with evaluating the perceived image quality of fine art reproduction created by representative museums in the United States under controlled and uncontrolled environments with and without the presence of the original artwork. The experimental results suggest that the image quality is highly correlated with the color accuracy of the reproduction only when the original is present and the reproduction is evaluated on a characterized display. We then examined the workflows to create these reproductions, and found that current workflows rely heavily on visual editing and retouching (global and local color adjustments on the digital reproduction) to improve the color accuracy of the reproduction. Visual editing and retouching can be both time-consuming and subjective in nature (depending on experts\u27 own experience and understanding of the artwork) lowering the efficiency of artwork digitization considerably. We therefore propose to improve the workflow of fine art reproduction by (1) automating the process of visual editing and retouching in current workflows based on RGB acquisition systems and by (2) recovering the spectral reflectance of the painting with off-the-shelf equipment under commonly available lighting conditions. Finally, we studied the perceived image quality of reproductions created by current three-channel (RGB) workflows with those by spectral imaging and those based on an exemplar-based method
High-fidelity colour reproduction for high-dynamic-range imaging
The aim of this thesis is to develop a colour reproduction system for high-dynamic-range (HDR)
imaging. Classical colour reproduction systems fail to reproduce HDR images because current characterisation
methods and colour appearance models fail to cover the dynamic range of luminance
present in HDR images. HDR tone-mapping algorithms have been developed to reproduce HDR
images on low-dynamic-range media such as LCD displays. However, most of these models have
only considered luminance compression from a photographic point of view and have not explicitly
taken into account colour appearance. Motivated by the idea to bridge the gap between crossmedia
colour reproduction and HDR imaging, this thesis investigates the fundamentals and the
infrastructure of cross-media colour reproduction. It restructures cross-media colour reproduction
with respect to HDR imaging, and develops a novel cross-media colour reproduction system for
HDR imaging. First, our HDR characterisation method enables us to measure HDR radiance values
to a high accuracy that rivals spectroradiometers. Second, our colour appearance model enables us
to predict human colour perception under high luminance levels. We first built a high-luminance
display in order to establish a controllable high-luminance viewing environment. We conducted a
psychophysical experiment on this display device to measure perceptual colour attributes. A novel
numerical model for colour appearance was derived from our experimental data, which covers the
full working range of the human visual system. Our appearance model predicts colour and luminance
attributes under high luminance levels. In particular, our model predicts perceived lightness
and colourfulness to a significantly higher accuracy than other appearance models. Finally, a complete
colour reproduction pipeline is proposed using our novel HDR characterisation and colour
appearance models. Results indicate that our reproduction system outperforms other reproduction
methods with statistical significance. Our colour reproduction system provides high-fidelity colour
reproduction for HDR imaging, and successfully bridges the gap between cross-media colour reproduction
and HDR imaging
Lightness, Brightness, and Transparency in Optical See-Through Augmented Reality
Augmented reality (AR), as a key component of the future metaverse, has leaped from the research labs to the consumer and enterprise markets. AR optical see-through (OST) devices utilize transparent optical combiners to provide visibility of the real environment as well as superimpose virtual content on top of it. OST displays distinct from existing media because of their optical additivity, meaning the light reaching the eyes is composed of both virtual content and real background. The composition results in the intended virtual colors being distorted and perceived transparent. When the luminance of the virtual content decreases, the perceived lightness and brightness decrease, and the perceived transparency increases. Lightness, brightness, and transparency are modulated by one physical dimension (luminance), and all interact with the background and each other. In this research, we aim to identify and quantify the three perceptual dimensions, as well as build mathematical models to predict them. In the first part of the study, we focused on the perceived brightness and lightness with two experiments: a brightness partition scaling experiment to build brightness scales, and a diffuse white adjustment experiment to determine the absolute luminance level required for diffuse white appearances on 2D and 3D AR stimuli. The second part of the research targeted at the perceived transparency in the AR environment with three experiments. The transparency was modulated by the background Michelson contrast reduction in either average luminance or peak-to-peak luminance difference to investigate, and later illustrated, the fundamental mechanism evoking transparency perception. The first experiment measured the transparency detection thresholds and confirmed that contrast sensitivity functions with contrast adaptation could model the thresholds. Subsequently, the transparency perception was investigated through direct anchored scaling experiment by building perceived transparency scales from the virtual content contrast ratio to the background. A contrast-ratio-based model was proposed predicting the perceived transparency scales. Finally, the transparency equivalency experiment between the two types of contrast modulation confirmed the mechanism difference and validated the proposed model
Modelling of colour appearance
A colour may have a different appearance under different viewing conditions. This
causes many problems in the colour reproduction industry. Thus the importance of
prediction of colour appearance has arisen. In this study, a mathematical model to
predict colour appearance was developed based on the investigation of the changes of
colour appearance under a wide range of media and viewing conditions.
The media studied included large cut-sheet transparency films, 35mm projected
slides, reflection samples and monitor colours. The viewing conditions varied were light
source, luminance level and viewing background. Colour appearance was studied using
the magnitude estimation technique.
In general, colours appeared more colourful, lighter and brighter with an increase
in luminance level. Background and flare light had considerable influence on colour
appearance for cut-sheet transparency media. Simultaneous contrast effects occurred
when a monitor colour was displayed against a chromatic surround. The monitor colour
appeared lighter with a darker induction field. When a coloured area was enlarged,
lightness tended to increase while colourfulness tended to decrease. Colour appearance
was also affected by the closest neighbouring colour. In this case, the hue of the colour
largely shifted towards the direction of the opponent hue of the induction colour.
The data obtained were applied to test three colour spaces and two colour
appearance models. For reflection media, the Hunt91 model performed the best.
However it was not satisfactory when applied to transmissive media. Based on these
results, the Hunt93 model was developed by modification of the Hunt91 model. The new
model widens the application range of the Hunt91 and is reversible
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