Image Filter Tester 1.1 - Generic Wavelet Filter

• This filter performs a multi-level wavelet decomposition, then applies user-defined transfer functions to each individual wavelet channels, then performs a multi-level wavelet reconstruction.
• This filter is ideal for testing any wavelet-based filtering such as noise reduction (by suppressing high spatial frequency detail channels) or wavelet compression (by reducing resolution of high spatial frequency detail channels).
• The built-in function parser accepts any function typed in C-style. It recognizes 13 operators, 44 function names, 2 constants plus unlimited number of independent variables. Please click here for a complete list.
• While you type your transfer functions, please use 'x' or 'x0' to represent the wavelet coefficient to be processed. The parser is NOT case-sensitive.
• This filter works for grayscale images or 24-bit color images.

• Here's a list of wavelet functions that have been implemented:

• Here's an illustration of 3-level wavelet decomposition, which results in 10 channels, where A represents Approximation, HD represents Horizontal Detail, VD represents Vertical Detail, DD represents Diagonal Detail, and the subscript indicates the decomposition level.
• The wavelet decomposition is usually applied to the approximation coefficients from the previous level of decomposition. From the top-left corner to the bottom-right corner in this illustration, the channels contain information of higher and higher spatial frequency.
• The total number of wavelet coefficients (of all channels) remain the same as the total number of pixels of the image.

This page was last modified on 02/29/2004.