Re: what does phase distortion look like in image processing?

From: Tim Wescott (tim_at_wescottnospamdesign.com)
Date: 11/16/04 

Date: Mon, 15 Nov 2004 21:45:30 -0800

lucy wrote:
> I read the following in Matlab Help Document of Image Processing ToolBoxes,
>
> "FIR filters can be designed to have linear phase, which helps prevent
> distortion. "
>
> I am wondering what does phase distortion look like in image processing?
>
> Also,
>
> "Another class of filter, the infinite impulse response (IIR) filter, is not
> as suitable for image processing applications. It lacks the inherent
> stability and ease of design and implementation of the FIR filter.
> Therefore, this toolbox does not provide IIR filter support..."
>
> I want to ask what kind of inherent stability issue does IIR filter have?
>
> Thanks lot!
>
>
These questions are probably best answered by running some images
through the applicable filters and seeing what the results are. Just
make yourself an all-pass filter with considerable phase distortion,
filter your image, and take a look.

Similarly, you can either filter your image with an IIR by hand and see
what it looks like, or you can whomp up a FIR filter with IIR-like
characteristics, and see how _that_ looks. 

-- 
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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