Colour image representation using real quaternions has shown to be very useful for linear and morphological colour filtering. This paper deals with the extension of first derivatives-based structure tensor for various quaternionic colour image representations. Classical corner and edge features are obtained from eigenvalues of the quaternionic colour structure tensors. We study the properties o...

The dyeing behaviour of annually renewable soybean protein fibres with Madder, Weld and Walnut seed husk, natural dyes, were investigated and their possible antimicrobial effects were evaluated. The results obtained from the dyeing of the Madder on the soybean fabric were compared with those on a wool fabric. It was shown that the amount of the amino acid content of the fibre has a great effect...

The 'colour-shading effect' describes the phenomenon whereby chromatic variations affect the magnitude of perceived shape-from-shading in luminance patterns. A previous study showed that in mixed colour-plus-luminance sine-wave plaids, impressions of depth in the luminance component were enhanced by non-aligned chromatic components, and suppressed by aligned chromatic components [Nature Neurosc...

This study investigates systematic individual differences in the way observers perceive different kinds of surface properties and their relationship to the dress, which shows striking individual differences in colour perception. We tested whether these individual differences have a common source, namely differences in perceptual strategies according to which observers attribute features in two-...

The visual system continually adjusts its sensitivity to the statistical properties of the environment through an adaptation process that starts in the retina. Colour perception and processing is commonly thought to occur mainly in high visual areas, and indeed most evidence for chromatic colour contrast adaptation comes from cortical studies. We show that colour contrast adaptation starts in t...

It is often assumed that colours in an image correlate with intrinsic surface properties (e.g. reeectance). Indeed, this goes a long way to explain the predominance of colour as feature for image indexing. Unfortunately the assumption is unfounded since the image of a scene viewed under two diierent coloured lights contains two diierent sets of colours; that is, image colour is a measure of the...

This study is a contribution to the study of the spatial evolution of the properties of the municipal lake of Yaounde-Cameroon. The objective was the characterization of the physico-chemical, bacteriological and organoleptic parameters of water of this lake in order to provide the scientifically exploitable data. To understand the sources and the evolution of the pollution of this lake, we carr...