Claudio Oleari | Università degli Studi di Parma (Italy) (original) (raw)

Papers by Claudio Oleari

Electronic Imaging: Processing, Printing, and Publishing in Color, 1998

In this paper, we approach color-image-difference metrics by a Euclidean color-difference formula... more In this paper, we approach color-image-difference metrics by a Euclidean color-difference formula for small-medium color differences in log-compressed OSA-UCS space, recently published (C. Oleari, M. Melgosa and R. Huertas, J. Opt. Soc. Am. A, 26(1):121-134, 2009). We start from previous imagedifference metrics by replacing the CIE color-difference formulae with the new one. Tests are made by using the Pearson-, Spearman-and Kendall-correlation coefficient. Particularly, we compare the calculated image-difference metrics in relation to the perceived image difference obtained with psychophysical experiments. Current results show improvements in the actual state of art, making this formula the future key for image-difference metrics.

The settlement of archives of reference images useful for the diagnosis of the preservation state... more The settlement of archives of reference images useful for the diagnosis of the preservation state of paintings and restorer actions can be obtained using a spectrophotometric scanner capturing spectral images. This scanner is built arranging a spectrometer between the objective lens and a black and white digital matrix camera. The paper describes the working principles of the scanner, its technical

A complete software on standard colorimetry, named "Colour & Colorimetry", has been dev... more A complete software on standard colorimetry, named "Colour & Colorimetry", has been developed for laboratory computations and didactics. This software will be part of a forthcoming book on colorimetry (ref. 1). Today, it is successfully used at the University of Parma and soon will be used in the European ERASMUS Master Program, entitled "Color in Informatics and MEdia Technology" (CIMET).

Journal of the Optical Society of America A, 2014

Today chromatic adaptation transforms (CATs) are reconsidered, since their mathematical inconsist... more Today chromatic adaptation transforms (CATs) are reconsidered, since their mathematical inconsistency has been shown in Color Res. Appl.38, 188 (2013) and by the CIE technical committee TC 8-11: CIECAM02 Mathematics. In 2004-2005 the author proposed an adaptation transform based on the uniform color scale system of the Optical Society of America (OSA-UCS) [J. Opt. Soc. Am. A21, 677 (2004); Color Res. Appl. 30, 31 (2005)] that transforms the cone-activation stimuli into adapted stimuli. The present work considers all the 37 available corresponding color (CC) datasets selected by CIE and (1) shows that the adapted stimuli obtained from CC data are defined up to an unknown transformation, and an unambiguous definition of the adapted stimuli requires additional hypotheses or suitable experimental data (as it is in the OSA-UCS system); (2) produces a CAT, represented by a linear transformation between CCs, associated with any CC dataset, whose high quality measured in ΔE units discards the possibility of nonlinear transformations; (3) analyzes these color-conversion matrices in a heuristic way with a reference adaptation that is approximately that of the OSA-UCS adapted colors for the D65 illuminant and particularly shows accordance with the Hunt effect and the Bezold-Brücke hue shift; (4) proposes the measurements of CC stimuli with a reference adaptation equal to that of the visual situation of the OSA-UCS system for defining adapted colors for any considered illumination adaptation and therefore for defining a general CAT formula.

Il Nuovo Cimento D, 1986

ABSTRACT Summary We have investigated the opportunity of using a symmetry descent scheme in the d... more ABSTRACT Summary We have investigated the opportunity of using a symmetry descent scheme in the description of low-symmetry molecular systems when they are derivable from higher symmetries by a set of small distortions which carry the system through intermediate symmetries. A method is given which allows us to determine the molecular configurations to be ascribed to a molecule for the various symmetries with least distortions with respect to the actual geometry. A criterion based on the extent of the distortion of such configurations is proposed for the choice of the symmetry to be taken as the «highest» and of the descent pathway. The classification of the states and the evaluation of the Hamiltonian matrix elements within the scheme of the symmetry descent are also discussed.

Vision Research, 1996

The confusion points of dichromats are derived from the constant-luminance planes of trichromats,... more The confusion points of dichromats are derived from the constant-luminance planes of trichromats, protanopes and deuteranopes experimentally defined by heterochromatic-flicker photometry: (1) the zero-luminance planes of the observers considered in this experiment intersect almost exactly in a line that crosses the plane of the chromaticity diagram in the tritanopic-confusion point and confirm that the short-wavelength sensitive cones can be considered to have no contribution to luminance; (2) protanopic-and deuteranopic-confusion points are taken as being defined by the intersection of the tangent line to the long-wavelength region of the spectrum locus and the zeroluminance plane for protanopes and deuteranopes, respectively.

Journal of the Optical Society of America A, 1993

... The 100 diagram is obtained from the 1964 CIE (xi(, yio) chromaticity diagram by the applicat... more ... The 100 diagram is obtained from the 1964 CIE (xi(, yio) chromaticity diagram by the application of two successive transformations: the first is a ... the Opti-cal Society of America Uniform Color Scales (OSA-ucs) system2 for integer values of lightness L are examined on theO 8l,81 ...

EURASIP Journal on Image and Video Processing, 2013

In this paper, we present a new metric to estimate the perceived difference in contrast between a... more In this paper, we present a new metric to estimate the perceived difference in contrast between an original image and a reproduction. This metric, named weighted-level framework E E (WLF-DEE), implements a multilevel filtering based on the difference of Gaussians model proposed by and the new Euclidean color difference formula in log-compressed OSA-UCS space proposed by . Extensive tests and analysis are presented on four different categories belonging to the well-known Tampere Image Database and on two databases developed at our institution, providing different distortions directly related to color and contrast. Comparisons in performance with other state-of-the-art metrics are also pointed out. Results promote WLF-DEE as a new stable metric for estimating the perceived magnitude of contrast between an original and a reproduction.

Color Research & Application, 2014

ABSTRACT Previous attempts to predict chromatic-adaptation correspondence have led to a sharpenin... more ABSTRACT Previous attempts to predict chromatic-adaptation correspondence have led to a sharpening dilemma—i.e., Von Kries primaries are chosen that do not include in the positive octant all the realizable (x,y) chromaticities. This leads to paradoxical adaptation predictions for the colors that have negative Von Kries coordinates. A solution is proposed here that expresses the asymmetric-matching relation of chromatic adaptation as the product of two matrix transformations, given source illuminant 1 and destination illuminant 2: from source tristimulus values via adaptation matrix 1 to the adapted state coordinates, and from the adapted state via the inverse of adaptation matrix 2 to the destination illuminant tristimulus values. To avoid the sharpening instability, the entire spectrum locus must lie within the positive octant of the adapted state tristimulus space. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 275–278, 2014; Published Online 14 March 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/col.21799

Color Research & Application, 2008

Color Research & Application, 2012

ABSTRACT In digital image capture, the camera signals produced by the D65 illuminant, once transl... more ABSTRACT In digital image capture, the camera signals produced by the D65 illuminant, once translated into tristimulus values of the CIE 1931 standard colorimetric observer (assuming the Maxwell‐Ives‐Luther criterion is satisfied), are considered good to produce accurate color rendering. An image obtained under any illuminant other than D65 does not appear realistic and the tristimulus values of the camera must be transformed into the corresponding ones produced by the D65 illuminant. This transformation must satisfy color constancy. In this work, the transformation is obtained by a color‐vision model based on the Optical Society of America‐Uniform Color Scales system [Color Res Appl 2005; 30: 31–41] and is represented by a matrix dependent on the adaptation illuminant. This matrix is obtained by minimizing the distance between the pairs of the uniform scale chromatic responses related to the tristimulus values of the 99 different color samples of the SG Gretag‐Macbeth ColorChecker measured under a pair of different illuminants, one of which is the D65. Then any picture captured under a given light source can be translated into the picture of the same scene under the D65 illuminant. Metameric reason allows only approximate solutions. The transformations from Daylight and Planckian illuminants to the D65 illuminant have a very regular dependence on the color temperature, that appears to be the typical parameter for the color conversion. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 412–422, 2013

Color Research & Application, 1999

Color Research & Application, 2000

The experimental data of the spectral-reflectance factor are considered as dependent on the instr... more The experimental data of the spectral-reflectance factor are considered as dependent on the instrument-spectral-bandwidth function in order to perform their deconvolution and to compute the tristimulus values. The deconvolution is performed by local-power expansion. In the case that the spectral-bandpass dependence regards only the spectral transmittance of the monochromator, the goodness of this technique is evaluated by simulation (1325 reflectance factors of the Munsell samples are considered as trial functions) and compared with other usual techniques: Stearns and Stearns method for bandpass error, ASTMweighting function interpolation, and Venable-ASTM weighting function. The zero order of the deconvoluted spectral-reflectance factor can be related to the Stearns and Stearns method for bandpass error. With respect to any other technique, the second-order deconvolution, for the CIE standard illuminants, gives color differences lower by a factor 0.1 or more for a bandpass ⌬ ϭ 10 nm, color differences lower by a factor 0.3 or more for a bandpass ⌬ ϭ 20 nm and, for the CIE fluorescent illuminants, color differences generally lower.

Color Research & Application, 2009

ABSTRACT In spectral measurements, a consequence of using finite bandwidth is that the observed q... more ABSTRACT In spectral measurements, a consequence of using finite bandwidth is that the observed quantity is the convolution of the instrument-spectral-bandpass function with the unknown quantity that we want measure. To know the true value of the quantity to be measured, we must perform a deconvolution of the observed data. This article proposes a deconvolution technique based on the complete knowledge of the instrument-spectral-bandpass function and on the hypothesis that the unknown quantity to be measured can be power expanded locally around each measuring wavelength. Typical spectral bandpass functions, triangular and Gaussian and with symmetric and asymmetric shape are considered. The spectral resolution evaluated by simulation as a function of the bandwidth and of the spectral scanning step is given to represent the performance of this technique. © 2009 Wiley Periodicals, Inc. Col Res Appl, 2010

ansatt.hig.no

Figura 1. Menù a pulsanti su due pagine. I due riquadri gialli ricordano le date degli ultimi agg... more Figura 1. Menù a pulsanti su due pagine. I due riquadri gialli ricordano le date degli ultimi aggiornamenti dei dati colorimetrici del monitor e del gamma.

Journal of The Optical Society of America A-optics Image Science and Vision, 2004

Many problems regarding color opponency are still unsolved. In this study the system of the unifo... more Many problems regarding color opponency are still unsolved. In this study the system of the uniform color scales of the Optical Society of America (OSA-UCS) is analyzed with the aim of obtaining answers to very general questions on color opponency. The perceptual color opponencies in the OSA-UCS system, represented by its coordinates (j, g), appear to work in a mutually interacting way. On the hypothesis that such an interaction is due to a linear mixing of a pair of independent opponent mechanisms with scales satisfying a proper Weber fraction, three chromatic opponency functions are derived, whose sum is equal to zero. These functions are the logarithms of the ratios of two tristimulus values in a proper reference frame (called the &amp;quot;main reference frame&amp;quot;) and therefore are antisymmetric and zero-degree homogeneous functions of these tristimulus values. Any pair of these three functions is a set of two independent functions. A new formula for color opponency in the OSA-UCS system is derived in which the perceptual color opponencies (j, g) are written as products of the lightness by a proper linear mixing of any pair of the three chromatic opponency functions. All this is possible because the lattice of the OSA-UCS system is composed of geodesic lines.

Lettere Al Nuovo Cimento, 1974

One of us recently proposed (1.2) an (~ eikonal perturbation theory ~ (EPT) to be used as an alte... more One of us recently proposed (1.2) an (~ eikonal perturbation theory ~ (EPT) to be used as an alternative to ordinary perturbation thcory (OPT) for discussing quantum field theories at high energy. It has been shown (1.2) that, unlike OPT, the EPT shares with the eikonal approximations (EA's) those properties desirable for describing highenergy behaviours. At the same time, and unlike the EA'S, the EPT shares (1,2) with OPT the properties of being a simple field-theoretic iterative calculation scheme, which can consistently take into aceout self-interactions, and is rcnormalizable if the OPT is such. In view of these properties the EPT for the vector-glnon-quark model has been advocated (8) as a potentially excellent theoretical laboratory for studying ideas and problems in hadron dynamics, within the rigorous framework of a renormalizable Lagrangian quantum field theory.

Color Research and Application, 2001

Color-space metrics are considered and three main aspects are analyzed: (1) the distinction betwe... more Color-space metrics are considered and three main aspects are analyzed: (1) the distinction between small and large color differences; (2) the relation between space metrics and color-difference formulae; (3) the color-scale comparison between CIE 1931 and CIE 1964 observers.The analysis, based on daylight adaptation, is made for the 2° visual field on a chromaticity diagram with uniform scales according with the MacAdam ellipses1 and, for the 10° visual field, on the OSA-UCS.2,3 The conclusions are: (i) the main difference between 2° and 10° observers is a proper dilation of the chromaticity scales; (ii) the chroma scale of the Munsell system is uniform for the 10° visual field; (iii) the scales of the Munsell system are in good agreement with those of OSA-UCS; (iv) the usual color-difference formulae (CMC, CIE94) represented on the OSA-UCS space show a distortion that seems due to their definition in the CIELAB space; the BFD formula shows a lower distortion. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 351–361, 2001