1,721,132 research outputs found
Colour perception may optimize biologically relevant surface discriminations - rather than type-I constancy
No full textColour selection strategies in colour design
Full text linkOur evolving hypothesis is that a colour-picker interface designed to challenge the novice user will better connect with their creative abilities and help develop their understanding of the interrelated digital colour challenges. An interface approach underpinned by a philosophy of engaging-in-use rather than ease-of-use may help to better rationalize a new user’s colour-selection process, thus improving their initial productivity and creativity within the digital design environment. This study challenges the established HCI (Human Computer Interaction) convention that consistently prescribes to a user-interface-strategy embracing ease-of-use. It considers if this ideal is necessarily the right approach for creative software application, assessing colour-pickers as the primary example. Interesting results are emerging from experimental work with an early prototype colour-picker tool that exploits our ongoing research into intuitive understanding of colour. The focus of this work is the creative colour selection process and not colour management per se, however it is recognised that the relationship between these two design and technical processes is not always mutually exclusive
Application of the four-colour theorem to the surfaces of polyhedra
Full text linkThe four-colour map theorem states that, given any separation of a plane into contiguous regions, producing a figure called a map, no more than four colours are required to colour the regions of the map so that no two adjacent regions have the same colour. Two regions are considered to be adjacent if they share a common boundary that is not a corner (a point shared by three or more regions). The theorem was proposed in the 1850s and became the first theorem to be proved by computational methods in the 1970s. Despite the theorem being true, some geopolitical maps require more than four colours (if, for example, some regions are not contiguous) and the theorem has never been of great interest to mapmakers. This paper describes the theorem and explores how it could be extended to three dimensions. We restrict our study to the colouring of the surfaces of three-dimensional polytopes or polyhedra, specifically those that are convex. An analysis of the relationship between two-dimensional maps and three-dimensional surfaces is presented with regard to the minimum number of colours required. Visual examples are provided for regular polyhedral of increasing number of polygonal faces
Study of the use of the colour blue in Byzantine and early post-Byzantine church decoration in the context of the presumed contemporary interior lighting
No full textThis paper presents the use of a new method of assessment and comparison of the appearance of colour in an art historical context, using some seventeenth century churches in Bulgaria as a case-study. The method also allows initial identification of the main colour agent of the pigments used. It contains the results of the identification of the colour red. This research provides a possible basis for further investigation into the use of colour in seventeenth century Bulgaria, in a way that overcomes the limitations of colour reproduction in print. In addition, a faithful and unambiguous record of the existing colours will make it possible to create the non-metameric subtractive mixtures that are needed for the restoration of the frescoes
Effect of background colour on monitor characterisation
No full textA common solution for transferring images from one device to another without loss of colour fidelity is to characterise each device in terms of CIE tristimulus values. For example, it would be possible with appropriate characterisation procedures to convert the LCD RGB values to CIE XYZ values and vice versa. Characterisation of devices into a standard colour space that is independent of the device reduces the number of transformations which may be required for adequate performance. The first stage in characterisation is to linearise the data termed "gamma correction" for certain devices and then transform the linearised values in CIE XYZ tristimulus values. In order to determine the non-linearity of the characterisation and the matrix for linear conversion between RGB and XYZ it is normal to make colour measurements of certain colour patches displayed on the system. However, it is known that the colour measurements of the patches may vary with the colour and luminance of the background against which they are displayed. Lack of spatial independence is one of the factors that can cause this phenomenon. This raises the question of what the nature of the background should be for an optimal characterisation of a display system. It is likely that what is optimal will depend upon the intended application of the characterised display (for example, is it being used to display simple images in a psychophysical experiment or more complex images in some other setting). This research considers characterisation with four background conditions (white, grey, black and a new Mondrian-like coloured background) and explores the effect of these background effects on the characterisation model’s parameters and on the usefulness of the characterisation in various imaging scenarios
CONDITIONS FOR PERCEPTUAL TRANSPARENCY
No full textWe review the conditions that are necessary for the perception of transparency and describe the spatio chromatic constraints for achromatic and chromatic transparent displays. These constraints can be represented by the convergence model and are supported by psychophysical data. We present an alternative representation of the constraints necessary for transparency perception that is based on an analogy with a model of colour constancy and the invariance of cone-excitation ratios. Recent psychophysical experiments are described that suggest that displays where the cone-excitation ratios are invariant produce a stronger impression of transparency than displays where the cone excitations are convergent. We argue that the spatial relations in an image are preserved when a Mondrian-like surface is partially covered by a transparent filter and therefore show an intriguing link between transparency perception and colour constancy. Finally, we describe experiments to relate the strength of the transparency percept with the number of unique patches in the image display. We find that the greater the number of surfaces in the display that are partially covered by a transparent filter the stronger the impression of transparenc
Complementary colour harmony in different colour spaces
No full textThis research investigates hue complementarity in different colour spaces namely CIELAB, CIELUV, Kuehni LAB, OSA-UCS, and Hunter Rdab colour spaces. A psychophysical experiment has determined the hue of colours that are deemed complementary to twenty standard fixed hues. The data were then analysed in CIELAB space and the other applied ones to explore in which colour space opposite hues best describe visual complementary relationships. In each space the opposite hues were calculated as 180 degrees from the standard fixed hues and compared with the psychophysically derive complementary hues. The results show that none of the five colour spaces can exactly predict complementary relationships; however OSA-UCS colour space performed better than the other four colour spaces. For OSA-UCS colour space, apart from a few hues, each complementary hue was within 1.0±4.5 degrees of the opposite hue. The computations were carried out under CIE illuminant D65 and for the 1964 standard observer. Previous investigations (Mahyar et al. 2011) was carried out in the other colour spaces, namely CIELAB, Munsell and Kuehnie LAB, under different conditions of CIE illuminant C and 1931 standard observer. Psychophysical experiment in CIELAB colour space were presented at a previous AIC meeting (Mahyar et al. 2007)
The city colour planning, between instances of conservation and need for renewal
No full textThe colour plans since their appearance, in Italy at the end of the Seventies, were a response to the need to protect and regulate, but also to enhance the colour identity of the historic city. The colour plans, then, have been assuming diversified objectives and intervention methods, which partly reflect and partly fuel the issue of the city chromatic identity poised between past, present and future. Starting from a reading of the various approaches and methods, objectives and results, characterising the colour plans, especially in Italy and in Europe, the aim of this paper is to present a summary of the main orientations the urban colour planning and design have been assuming
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