16 research outputs found
Occlusions and their relationship with the distribution of contrasts in natural images
AbstractAn Information-Theory-like hypothesis recently proposed for early visual processing (the Minimal Local-Asperity hypothesis) accounts for the adaptive behavior with intensity of horizontal cells. It has been shown that for this to hold, the probability that a point is traversed by an occluding border must increase supralinearly (that is, with a positive second derivative) as a function of contrast. We test this condition by analyzing the distribution of contrasts and their relationship with occluding borders in natural images. We find that the distribution of contrasts in natural images falls exponentially as a function of contrast. Moreover, the probability that a point is traversed by an occluding border in natural images always rises with contrast until reaching one. This rise tends to be supralinear and addition of noise (at low intensities) increases the supralinearity, shifting the rising portion of the curve towards higher contrasts. These findings lend support to the Minimal Local-Asperity hypothesis, which proposes that one of the main roles of early retinal processing is to extract optimally edge, contrast, and luminance attributes from the visual world based on previous knowledge about natural images
The role of early retinal lateral inhibition: More than maximizing luminance information
Colour measurement of natural stones using a calibrated digital camera
Natural stones (marbles, granites, etc.) are used as building materials like ceramic tiles and
artificial stones. In this work, we evaluate whether automatic natural-stone classification can be
performed based on colorimetric calibration and S-CIELAB model of human colour perception. We
found significant differences between the histograms of the ΔE S-CIELAB model from different
marble types, which might be taken into account on industrial applications.This work was supported by the Spanish Ministerio de Educación y Ciencia from the Ramón
y Cajal Program Grant 2904/01 to R.M.B., and by the Spanish Generalitat Valenciana CoreGrant
CTBCDPT/04/006 to the University of Alicante