4,556 research outputs found
Colour constancy using von Kries transformations: colour constancy "goes to the Lab"
Colour constancy algorithms aim at correcting colour towards a correct perception within
scenes. To achieve this goal they estimate a white point (the illuminant's colour), and correct
the scene for its in uence. In contrast, colour management performs on input images colour
transformations according to a pre-established input pro le (ICC pro le) for the given con-
stellation of input device (camera) and conditions (illumination situation). The latter case
presents a much more analytic approach (it is not based on an estimation), and is based on
solid colour science and current industry best practises, but it is rather in exible towards cases
with altered conditions or capturing devices. The idea as outlined in this paper is to take up
the idea of working on visually linearised and device independent CIE colour spaces as used
in colour management, and to try to apply them in the eld of colour constancy. For this
purpose two of the most well known colour constancy algorithms White Patch Retinex and
Grey World Assumption have been ported to also work on colours in the CIE LAB colour
space. Barnard's popular benchmarking set of imagery was corrected with the original imple-
mentations as a reference and the modi ed algorithms. The results appeared to be promising,
but they also revealed strengths and weaknesses
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An Evaluation of a Battery of Functional and Structural Tests as Predictors of Likely Risk of Progression of Age-Related Macular Degeneration.
Purpose: To evaluate the ability of visual function and structural tests to identify the likely risk of progression from early/intermediate to advanced AMD, using the Age-Related Eye Disease Study (AREDS) simplified scale as a surrogate for risk of progression. The secondary aim was to determine the relationship between disease severity grade and the observed functional and structural deficits. Methods: A total of 100 participants whose AMD status varied from early to advanced were recruited. Visual function was assessed using cone dark adaptation, 14 Hz flicker and chromatic threshold tests and retinal structure was assessed by measuring drusen volume and macular thickness. The predictive value of the tests was estimated using ordinal regression analysis. Group comparisons were assessed using analysis of covariance. Results: Change in cone dark adaptation (cone Ï„) and yellow-blue (YB) chromatic sensitivity were independent predictors for AMD progression risk (cone Ï„, pseudo R2 = 0.35, P < 0.001; YB chromatic threshold, pseudo R2 = 0.16, P < 0.001). The only structural predictor was foveal thickness (R2 = 0.05, P = 0.047). Chromatic sensitivity and cone dark adaptation were also the best functional tests at distinguishing between severity groups. Drusen characteristics clearly differentiated between participants with early and advanced disease, but were not able to differentiate between those with early AMD and controls. Mean differences in retinal thickness existed between severity groups at the foveal (P = 0.040) and inner (P = 0.001) subfields. Conclusions: This study indicates that cone Ï„, YB chromatic threshold and foveal thickness are independent predictors of likely risk of AMD progression
The CIECAM02 color appearance model
The CIE Technical Committee 8-01, color appearance models for color management applications, has recently proposed a single set of revisions to the CIECAM97s color appearance model. This new model, called CIECAM02, is based on CIECAM97s but includes many revisions1-4 and some simplifications. A partial list of revisions includes a linear chromatic adaptation transform, a new non-linear response compression function and modifications to the calculations for the perceptual attribute correlates. The format of this paper is an annotated description of the forward equations for the model
Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 127, April 1974
This special bibliography lists 279 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1974
The LLAB model for quantifying colour appearance
A reliable colour appearance model is desired by industry to achieve high colour
fidelity between images produced using a range of different imaging devices. The aim
of this study was to derive a reliable colour appearance model capable of predicting
the change of perceived attributes of colour appearance under a wide range of
media/viewing conditions. The research was divided into three parts: characterising
imaging devices, conducting a psychophysical experiment, and developing a colour
appearance model.
Various imaging devices were characterised including a graphic art scanner, a
Cromalin proofing system, an IRIS ink jet printer, and a Barco Calibrator. For the
former three devices, each colour is described by four primaries: cyan (C), magenta
(M), yellow (Y), and black (K). Three set of characterisation samples (120 and 31
black printer, and cube data sets) were produced and measured for deriving and
testing the printing characterisation models. Four black printer algorithms (BPA),
were derived. Each included both forward and reverse processes. A 2nd BPA printing
model taking into account additivity failure, grey component replacement (GCR)
algorithm gave the most accurate prediction to the characterisation data set than the
other BPA models. The PLCC (Piecewise Linear interpolation assuming Constant
Chromaticity coordinates) monitor model was also implemented to characterise the
Barco monitor.
The psychophysical experiment was conducted to compare Cromalin hardcopy
images viewed in a viewing cabinet and softcopy images presented on a monitor
under a wide range of illuminants (white points) including: D93, D65, D50 and A.
Two scaling methods: category judgement and paired comparison, were employed by
viewing a pair of images. Three classes of colour models were evaluated: uniform
colour spaces, colour appearance models and chromatic adaptation transforms. Six
images were selected and processed via each colour model. The results indicated that
the BFD chromatic transform gave the most accurate predictions of the visual results.
Finally, a colour appearance model, LLAB, was developed. It is a combination of the
BFD chromatic transform and a modified version of CIELAB uniform colour space to
fit the LUTCRI Colour Appearance Data previously accumulated. The form of the
LLAB model is much simpler and its performance is more precise to fit experimental
data than those of the other models
Status of CIE Color Appearance Models
In meetings just prior to the 1997 AIC Congress in Kyoto, CIE TC1-37, chaired by M. Fairchild, established the CIE 1997 Interim Colour Appearance Model (Simple Version), known as CIECAM97s. CIECAM97s was formally published in 1998 in CIE publication 131. CIE TC1-37 was dissolved shortly after publication of CIECAM97s at which time, a reportership, R1-24 held by M. Fairchild, was established to monitor ongoing developments in color appearance modeling and notify CIE Division 1 if it became necessary to form a new TC to consider revision or replacement of CIECAM97s. In the four years between AIC Congresses, there has been much activity, both by individual researchers and within the CIE, aimed at furthering our understanding of color appearance models and deriving improved models for consideration. The aim of this paper is to summarize these activities, report on the current status of CIE efforts on color appearance models, and suggest what the future might hold for CIE color appearance models
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