foxyshadis
10th June 2010, 03:50
I'm hoping some of the developers who've incorporated it can help me. The FFTW docs give you a lot of information on how to call it, but are pretty sparse on the final result, assuming you're already very familiar how to use FFT in matlab and so on. I'm not.
I can translate a 2d raw image to an fft, but I'm not sure how to make use of it. I need to know exactly what the layout means. I'm using fftwf_plan_r2r_2d with FFTW_REDFT10 in both dimensions, which is a standard DCT according to the docs. I know that the first item is the average*count*4. Following that, how do I conceptualize the data? I think it might be: for each row, terms for 0 to 1 then -1 to 0; does that start at x/2 where x is the length, and how should I reorder it to work with it? Once it's put in a useful order, how would I merge the data into a few (say 4) buckets to derive frequency power statistics from? I'm using (sum of squares) / (sum of squared count) currently, treating the data as a square and taking slices out of it similar to:
0 1 2 3
1 1 2 3
2 2 2 3
3 3 3 3
Obviously a lot of newbie questions, sorry.
I can translate a 2d raw image to an fft, but I'm not sure how to make use of it. I need to know exactly what the layout means. I'm using fftwf_plan_r2r_2d with FFTW_REDFT10 in both dimensions, which is a standard DCT according to the docs. I know that the first item is the average*count*4. Following that, how do I conceptualize the data? I think it might be: for each row, terms for 0 to 1 then -1 to 0; does that start at x/2 where x is the length, and how should I reorder it to work with it? Once it's put in a useful order, how would I merge the data into a few (say 4) buckets to derive frequency power statistics from? I'm using (sum of squares) / (sum of squared count) currently, treating the data as a square and taking slices out of it similar to:
0 1 2 3
1 1 2 3
2 2 2 3
3 3 3 3
Obviously a lot of newbie questions, sorry.