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arXiv · 2207.13674

Fast expansion into harmonics on the disk: a steerable basis with fast radial convolutions

Nicholas F. Marshall·Oscar Mickelin·Amit Singer
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Abstract

We present a fast and numerically accurate method for expanding digitized $L \times L$ images representing functions on $[-1,1]^2$ supported on the disk $\{x \in \mathbb{R}^2 : |x|<1\}$ in the harmonics (Dirichlet Laplacian eigenfunctions) on the disk. Our method, which we refer to as the Fast Disk Harmonics Transform (FDHT), runs in $O(L^2 \log L)$ operations. This basis is also known as the Fourier-Bessel basis, and it has several computational advantages: it is orthogonal, ordered by frequency, and steerable in the sense that images expanded in the basis can be rotated by applying a diagonal transform to the coefficients. Moreover, we show that convolution with radial functions can also be efficiently computed by applying a diagonal transform to the coefficients.

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Nicholas F. Marshall, Oscar Mickelin, Amit Singer. 2022-07-27. Fast expansion into harmonics on the disk: a steerable basis with fast radial convolutions. https://arxiv.org/abs/2207.13674

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