[geeks] Re: [rescue] Spaceballs.

[Dave McGuire]

On December 8, Joshua D Boyd wrote:
> Apparently FFTs can be applied to any number of dimensions.  However, I also
> understood an FFT as something that required 2 inputs, a time and a value, and
> returned to inputs, a frequency for that value.  In fact, most descriptions 
> I've read about FFTs state that it is a transformation from the time domain
> to the frequency domain.  Well, fine.  But, what is the time domain for a 
> single image?  Which is to day that I'm far from understanding the forces at
> work here.

  FFTs can be used to convert from the time domain to the frequency
domain OR the inverse.

  The time domain for a single image (take a single-channel image for
simplicity) is luminance.  Look at it this way...take an image as a
2-d array of integer pixels.  Iterate through the rows and columns
sequentially, as they would be stored in memory.  Plot the luminance
(the integer pixel value).  Bang, there's your time-domain signal.

      -Dave

-- 
Dave McGuire
St. Petersburg, FL