matlab fft2怎么移动频率对称,[MATLAB图像处理] 对二维矩阵做fft2，如何像一维时域变换那样确定各个元素的频率...

对二维矩阵做fft2，如何像一维时域变换那样确定各个元素的频率

假设现在有个5x5的二维矩阵A, 其横坐标对应x,纵坐标对应y,并且已知dx和dy的数值。我的问题是在对A做如下处理C=fftshift(fft2(A))之后如何求C中各个元素对应的频率值(也有称C中数据是波数域数据的)，就像一维fft变换之后可以求得各个数据对应的频率值 0*df, 1*df, 2*df, 3*df...那样，只不过这里是二维的。我需要对C中的所有数据进行波数域计算之后再做ifft2变回时域中。还请高手指教！！谢谢

>> A=randn(5)

A =

-0.548663858017295 -0.844070275018183 0.143552000426655 -1.457842254811370 -0.064050458771001

-2.200449471069738 -1.214233420441409 0.780401289153117 0.900824520634748 0.118022180317756

-1.263137367482780 -1.106181850556560 0.857441415847785 0.470812866650541 -0.061153603398749

-0.416378216720860 0.796695025372485 -0.625638087370599 -1.393605673987658 -0.831023318540768

0.326857590138703 0.277352631564569 -1.722887278776487 -0.414668993490137 1.103528947235693

>> B=fft2(A)

B =

1 至 3 列

-8.388495661111545 + 0.000000000000000i -2.674278127910126 + 1.460266361730422i -3.385902349414028 + 2.647065743796523i

-0.513147199215627 + 0.323656991354603i 2.422818693196944 +10.056982226891011i 1.898686986572818 + 0.068680454961608i

-2.220292085706588 + 1.997678833120481i -1.839240871560157 - 2.883051357725220i 1.001143470221256 + 2.952029685034170i

-2.220292085706588 - 1.997678833120481i 3.677085493031505 - 2.957946891609061i 1.621828775725694 + 1.623613999397101i

-0.513147199215627 - 0.323656991354603i -0.416412418577132 - 6.673415325554997i -2.236340761024977 + 2.616113047249227i

4 至 5 列

-3.385902349414028 - 2.647065743796523i -2.674278127910126 - 1.460266361730422i

-2.236340761024977 - 2.616113047249227i -0.416412418577132 + 6.673415325554997i

1.621828775725694 - 1.623613999397101i 3.677085493031505 + 2.957946891609061i

1.001143470221256 - 2.952029685034170i -1.839240871560157 + 2.883051357725220i

1.898686986572818 - 0.068680454961608i 2.422818693196944 -10.056982226891011i

>> C=fftshift(B)

C =

1 至 3 列

1.001143470221256 - 2.952029685034170i -1.839240871560157 + 2.883051357725220i -2.220292085706588 - 1.997678833120481i

1.898686986572818 - 0.068680454961608i 2.422818693196944 -10.056982226891011i -0.513147199215627 - 0.323656991354603i

-3.385902349414028 - 2.647065743796523i -2.674278127910126 - 1.460266361730422i -8.388495661111545 + 0.000000000000000i

-2.236340761024977 - 2.616113047249227i -0.416412418577132 + 6.673415325554997i -0.513147199215627 + 0.323656991354603i

1.621828775725694 - 1.623613999397101i 3.677085493031505 + 2.957946891609061i -2.220292085706588 + 1.997678833120481i

4 至 5 列

3.677085493031505 - 2.957946891609061i 1.621828775725694 + 1.623613999397101i

-0.416412418577132 - 6.673415325554997i -2.236340761024977 + 2.616113047249227i

-2.674278127910126 + 1.460266361730422i -3.385902349414028 + 2.647065743796523i

2.422818693196944 +10.056982226891011i 1.898686986572818 + 0.068680454961608i

-1.839240871560157 - 2.883051357725220i 1.001143470221256 + 2.952029685034170i