In computer vision, one often wants to analyse oriented image structures, like edges under a certain angle. One could filter the image with a range of oriented kernels which cover the whole continuum of angles present in the image. However, this would demand a high computational cost. In literature, it is shown that one can restrict the computations to filter the image with a fixed set of basic kernels, and interpolate the image filtered with a kernel under an arbitrary direction from the results of the image filtered with the basic kernels [1, 2]. Such a set of kernels is called a steerable filter set.
My publications (with pdf's online) can be found here. Most of them use steerable pyramids.
in which you can find a Fourier-domain based implementation in C++ of the real and the complex steerable pyramid can be found here. This software is part of my larger image processing source code STIRA
 W. T. Freeman and E. H. Adelson, "The design and use of steerable filters", IEEE Trans. Pattern Analysis and Machine Intelligence, vol. 13, no. 9, pp. 891--906, 1991.
 E. P. Simoncelli, W. T. Freeman, E. H. Adelson, and D. J. Heeger, "Shiftable multi-scale transforms," IEEE Trans. Informations Theory, vol. 38, no. 2, 1992.