Análisis cromático y espectral de lacas acrílicas para retoque de pintura automotriz blanca mediante Reconocimiento de Pautas no Supervisado

The color of white acrylic lacquers utilized to touch up automotive paint was characterized in this paper using the CIELab color space and the whiteness index, with standard illuminant D65 and the standard observer at ten degrees. Based on this information, the color trends used in this type of product in the national market were recognized. In addition, the chemometric techniques of the Principal Component Analysis, Cluster Analysis, and Hierarchical Analysis allowed for recognition of similarities between the observed colors, which found, among other aspects, the greatest visual difference in the pearl white lacquer. On the other hand, the Alaskan white lacquer from Mazda and the universal white lacquer from Nissan were the most similar. It is also concluded that the chromatic and chemometric analyses of spectral data complemented each other; therefore, both are recommended for quality control purposes.En este trabajo, se caracterizó el color de lacas acrílicas blancas utilizadas para retocar pintura automotriz, mediante el espacio de color CIELab y el índice de blancura, utilizando el iluminante estándar D65 y el observador estándar a diez grados. A partir de tal información, fue posible reconocer las tendencias del color usado en este tipo de productos en el mercado nacional. Por otra parte, la aplicación de las técnicas quimiométricas de Análisis de Componentes Principales, Análisis de Grupos y Análisis Jerárquico, permitió reconocer semejanzas entre los colores observados, encontrando, entre otros, la mayor diferencia visual en la laca de blanco aperlado. Por otro lado, la laca de blanco Alaska de Mazda y la de blanco universal de Nissan fueron las más parecidas. También se concluye que el análisis cromático y el quimiométrico de datos espectrales fueron complementarios, por lo que se recomiendan ambos en el nivel de control de calidad

A Quadratic Model with Nonpolynomial Terms for Remote Colorimetric Calibration of 3D Laser Scanner Data Based on Piecewise Cubic Hermite Polynomials

The processing of intensity data from terrestrial laser scanners has attracted considerable attention in recent years. Accurate calibrated intensity could give added value for laser scanning campaigns, for example, in producing faithful 3D colour models of real targets and classifying easier and more reliable automatic tools. In cultural heritage area, the purely geometric information provided by the vast majority of currently available scanners is not enough for most applications, where indeed accurate colorimetric data is needed. This paper presents a remote calibration method for self-registered RGB colour data provided by a 3D tristimulus laser scanner prototype. Such distinguishing colour information opens new scenarios and problems for remote colorimetry. Using piecewise cubic Hermite polynomials, a quadratic model with nonpolynomial terms for reducing inaccuracies occurring in remote colour measurement is implemented. Colorimetric data recorded by the prototype on certified diffusive targets is processed for generating a remote Lambertian model used for assessing the accuracy of the proposed algorithm. Results concerning laser scanner digitizations of artworks are reported to confirm the effectiveness of the method

A neural field model for color perception unifying assimilation and contrast

37 pages, 17 figures, 3 ancillary filesInternational audienceWe propose a neural field model of color perception in context, for the visual area V1 in the cortex. This model reconciles into a common framework two opposing perceptual phenomena, simultaneous contrast and chromatic assimilation. Previous works showed that they act simultaneously, and can produce larger shifts in color matching when acting in synergy with a spatial pattern. At some point in an image,the color perceptually seems more similar to that of the adjacent locations, while being more dissimilar from that of remote neighbors. The influence of neighbors hence reverses its nature above some characteristic scale. Our model fully exploits the balance between attraction and repulsion in color space, combined at small or large scales in physical space. For that purpose we rely on the opponent color theory introduced by Hering, and suppose a hypercolumnar structure coding for colors. At some neural mass, the pointwise influence of neighbors is spatially integrated to obtain the final effect that we call a color sensation. Alongside this neural field model, we describe the search for a color match in asymmetric matching experiments as a mathematical projector. We validate it by fitting the parameters of the model to data from (Monnier and Shevell, 2004) and (Monnier, 2008) and our own data. All the results show that we are able to explain the nonlinear behavior of the observed shifts along one or two dimensions in color space, which cannot be done using a simple linear model

Colour Information In Design: Understanding Colour Meaning In Packaging Design

Colour is a powerful visual cue that affects consumer brand choice. Although there is an obvious and recognised value in the use of colour information in design, the literature demonstrates that colour information is an underexplored area that has not yet been addressed in detail by design research either practically or theoretically. Moreover, colour crosses various disciplines; due to its multi-disciplinary nature, it is not clear whether colour information is being effectively utilised in design. The aim of this study was to identify which types of colour information are useful in packaging, and to suggest a prototype tool (at concept level) to deliver this useful colour information to design professionals. An analysis of the relevant literature revealed 13 types of colour information which were then selected as basis for the study. Subsequently, the research design consisted of two phases. The first phase was exploratory in order to gain rich insight into the characteristics of useful colour information through interviews, an online survey, a colour meaning experiment, a colour meaning framework, and a colour meaning case study. The second phase was practice-based. Based on the informed exploration from the early studies, a web-based colour tool prototype, referred to as the CMCW (colour-meaning-centred website), was created, refined, and tested. The primary contribution of this study stems from an understanding of colour information to support design professionals; the identification of the five types (harmony, perception, meaning, psychology and printing) and the characteristics of useful colour information; and the formation of a colour-meaning framework and colour-meaning web tool. The secondary contribution of this study is the methodological approach undertaken that was used to understand the relationship between colour meaning and context by conducting a design-focused colour experiment. Research evidence highlights the importance and value of colour meaning information in design. The insight from this work will help researchers, design professionals, and colour-tool developers to make informed decisions on what they should focus on, how they should do so, and why. This will facilitate better provisions and uptake of useful colour information for design professionals in the design process and strategy fields. The framework also could support understanding of colour design practice in an analytic way, and be employed as a research tool in various design- or marketing-related research to investigate and analyse colour

The structure and properties of color spaces and the representation of color images

This lecture describes the author's approach to the representation of color spaces and their use for color image processing. The lecture starts with a precise formulation of the space of physical stimuli (light). The model includes both continuous spectra and monochromatic spectra in the form of Dirac deltas. The spectral densities are considered to be functions of a continuous wavelength variable. This leads into the formulation of color space as a three-dimensional vector space, with all the associated structure. The approach is to start with the axioms of color matching for normal human vi