Patent ID: 7660446

Claim:
A digital-signal processing apparatus for processing image data comprising: a partial-image extracting unit that extracts partial image data from real image data input, said partial image data having a partial image data size; a data-size selecting unit that (a) selects a fast Fourier transform (FFT) decomposable data size from a plurality of candidate data sizes, each of said candidate data sizes falling in a range close to the partial image data size, said FFT decomposable data size complying with a data-decomposing condition, and (b) outputs selected data from the partial image data, said selected data having the selected FFT decomposable data size; and an FFT filter unit for decomposing the selected data into data items and for performing Fourier transform on each data item, thereby effecting convolution on the data item, wherein the data-decomposing condition comprises at least one of (a) the FFT decomposable data size can be decomposed into products of prime numbers eciual to or smaller than a preset prime number; and (b) can be decomposed into 2's powers.