🚀 go-pugleaf

In article <1992Sep28.211714.17597@lmpsbbs.comm.mot.com> johna@comm.mot.com writes:

In article <1992Sep22.163256.15935@versyss.com>, keithd@versyss.UUCP (Keith Doyle) writes...
>I'm interested in using FFT for noise reduction of images, and while I
>have worked with FFT in 1D (for audio) and have an assortment of FFT
>source code for 1D, I don't really know how to apply it to the 2D case.
>Is it simply an FFT of all the rows combined with an FFT of all the columns
>of pixels in the image?  

>>    Here is the basic idea: Start with a 2-d array (matrix) of pixels. First,
>>take the 1-d FFT of each row vector, forming an intermdiate matrix from the 
>>result. Now take the 1-d FFT of each column vector in this matrix. The columns
>>of the final output matrix are formed from these transforms. Therefore, the
>>calculation of a 2-d FFT for an NxN matrix requires calculation of N^2 1-D
>>FFT's.

One thing to watch out for is where the DC component of the 2-D FFT ends
up in the result.  Very likely to be at the "corners" of the resulting
array, requiring some reorganization to move to the "center".

Rob Lake
BP Research
lake@rcwcl1.dnet.bp.com