Orthogonal and biorthogonal wavelets became very popular image processing tools but exhibit major drawbacks, namely a poor
resolution in orientation and the lack of translation invariance due to aliasing between subbands. Alternative multiresolution
transforms which specifically solve these drawbacks have been proposed. These transforms are generally overcomplete and consequently
offer large degrees of freedom in their design. At the same time their optimization gets a challenging task. We propose here
the construction of log-Gabor wavelet transforms which allow exact reconstruction and strengthen the excellent mathematical
properties of the Gabor filters. Two major improvements on the previous Gabor wavelet schemes are proposed: first the highest
frequency bands are covered by narrowly localized oriented filters. Secondly, the set of filters cover uniformly the Fourier
domain including the highest and lowest frequencies and thus exact reconstruction is achieved using the same filters in both
the direct and the inverse transforms (which means that the transform is self-invertible). The present transform not only
achieves important mathematical properties, it also follows as much as possible the knowledge on the receptive field properties
of the simple cells of the Primary Visual Cortex (V1) and on the statistics of natural images. Compared to the state of the
art, the log-Gabor wavelets show excellent ability to segregate the image information (e.g. the contrast edges) from spatially
incoherent Gaussian noise by hard thresholding, and then to represent image features through a reduced set of large magnitude
coefficients. Such characteristics make the transform a promising tool for processing natural images.
Keywords wavelet transforms - log-Gabor filters - oriented high-pass filters - image denoising - visual system