7. Nonlinear filters, such as the median filter, can reduce noise without
blurring edges.
8. Transform domain methods accomplish image enhancement based on
computations performed in a transform domain, such as the Fourier or
wavelet transform. Often, salient image features can be more easily
isolated and extracted in the transform domain than in the spatial
domain.
9. Commonly used Fourier domain image enhancement methods include
Wiener filtering, least-squares deconvolution, and bandpass filtering.
The Wiener filter is optimal for noise removal in the sense of minimum
mean square error.
10. Wavelet domain image enhancement methods leverage the advantages
of multiscale image representation and nonlinear filtering. Since image
edges tend to correlate spatially ...