Three Quick and Easy Matlab 2D Filter Functions

In image processing (indeed in any signal processing), filtering is one of the most important and frequenctly used operations. However, many situations, especially in the initial stages of development, do not require an extremely specialized or optomized filter. The following three Matlab functions provide a very quick method to create the impulse response of two dimensional low, high, and bandpass filters. The functions all involve creating a frequency domain prototype and then calculating the filter coefficients using intrinsic Matlab functions. The three functions automatically create the prototype and return the time domain impulse response. All three functions take as arguments the desired order (or size) of the returned impulse response and the normalized frequency cutoff(s). As indicated below, the resultant filter is not identical to the desired. However, as expected, the resultant filter improves as the order is increased:

Eleventh Order Band Pass Filter

Twenty-Second Order Band Pass 
Filter

These functions were created in Matlab for Windows 4.2 from The MathWorks, Inc. and require the Image Processing Toolbox.

Feel free to use and modify the code as you see fit. E-mail me if you have any comments or corrections about the preceding discussion!!


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HartkePM@saber.udayton.edu. This page was last modified on
28 September 1996 by Paul Hartke.