We discussed the decomposition of a signal (or image) into a lowpass- and highpass-filtered component. Wavelet-based filters can be envisioned as algorithms where wavelet decomposition takes place, followed by an attenuation of either the lowpass-filtered component or the highpass-filtered component. An inverse wavelet transform then restores the filtered image. The underlying principle can be seen […]
Wavelet-Based Highpass Filtering The complementary operation to wavelet-based lowpass filtering is wavelet-based highpass filtering, a process analogous to highpass filtering in the frequency domain. To create a wavelet-based highpass filter, the wavelet coefficients of the lowest detail level, that is, the lowpass output of the last subband stage (the Xk), need to be attenuated. Although […]