Image Processing Toolbox User's Guide Previous page   Next Page

Windowing Method

The windowing method involves multiplying the ideal impulse response with a window function to generate a corresponding filter, which tapers the ideal impulse response. Like the frequency sampling method, the windowing method produces a filter whose frequency response approximates a desired frequency response. The windowing method, however, tends to produce better results than the frequency sampling method.

The toolbox provides two functions for window-based filter design, fwind1 and fwind2. fwind1 designs a two-dimensional filter by using a two-dimensional window that it creates from one or two one-dimensional windows that you specify. fwind2 designs a two-dimensional filter by using a specified two-dimensional window directly.

fwind1 supports two different methods for making the two-dimensional windows it uses:

The example below uses fwind1 to create an 11-by-11 filter from the desired frequency response Hd. Here, the hamming function from the Signal Processing Toolbox is used to create a one-dimensional window, which fwind1 then extends to a two-dimensional window.

Desired Two-Dimensional Frequency Response (left) and Actual Two-Dimensional Frequency Response (right)

Previous page  Frequency Sampling Method Creating the Desired Frequency Response Matrix Next page

© 1994-2005 The MathWorks, Inc.