An object-oriented model for brightness perception.

An object-oriented model for the brightness perception of static images is presented. The philosophy behind the model is that the visual system aims at a brightness representation that displays object properties, and consequently is insensitive to variations in light source and changes in viewing position. The model assumes an ensemble of neural units that differ in receptive field size, i.e. identical operations are performed at a number of (spatial) scales. The brightness at each retinal position is the weighted sum of the neural activities that exist at this position in the different scales. The weighting function is such that the brightness impression is robust against variation in viewing distance. The operating characteristics of the neural units are derived from ganglion cell behaviour, and are robust against variation in light level. The model is able to unify different aspects of brightness perception, such as brightness induction and brightness assimilation. In order to gain in transparency, the approach adopted in this paper is a general one: we aim at showing how different aspects of brightness perception can be explained and unified within the model, at the expense of a less detailed description of psychophysical data.