Meanwhile biorthogonal wavelets got a very popular image processing tool, alternative multiresolution transforms have been proposed for solving some of their drawbacks, namely the poor selectivity in orientation and the lack of translation invariance due to the aliasing between subbands. These transforms are generally overcomplete and consequently offer huge degrees of freedom in their design. At the same time their optimization get a challenging task. We proposed here a log-Gabor wavelet transform gathering the excellent mathematical properties of the Gabor functions with a carefully construction to maintain the properties of the filters and to permit exact reconstruction. Two major improvements are proposed: first the highest frequency bands are covered by narrowly localized oriented filters. And second, all the frequency bands including the highest and lowest frequencies are uniformly covered so as 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 transform is optimized not only mathematically but it also follows as much as possible the knowledge on the receptive field of the simple cells of the Primary Visual Cortex (V1) of primates and on the statistics of natural images. Compared to the state of the art, the log-Gabor wavelets show excellent behavior in their ability to segregate the image information (e.g. the contrast edges) from incoherent Gaussian noise by hard thresholding and to code the image features through a reduced set of coefficients with large magnitude. Such characteristics make the transform a promising tool for general image processing tasks.
This library defines the set of LogGabor kernels. These are generic edge-like filters at different scales, phases and orientations. The library develops a simple method to construct a simple multi-scale linear transform.