static void FFT(ref Complex[] data, FFTDirection direction)
{
int n = data.Length;
int i, j, istep;
int m, mmax;
double r, r1, theta, w_r, w_i, temp_r, temp_i;
r = Math.PI;
if(FFTDirection.Forward == direction) { r = -r; }
j = 0;
for(i = 0; i < n; i++)
{
if(i < j)
{
temp_r = data[j].Re;
temp_i = data[j].Im;
data[j].Re = data[i].Re;
data[j].Im = data[i].Im;
data[i].Re = temp_r;
data[i].Im = temp_i;
}
m = n >> 1;
while(j >= m)
{
j -= m;
m = (m + 1) / 2;
}
j += m;
}
mmax = 1;
while(mmax < n)
{
istep = mmax << 1;
r1 = r / (double)mmax;
for(m = 0; m < mmax; m++)
{
theta = r1 * m;
w_r = Math.Cos(theta);
w_i = Math.Sin(theta);
for(i = m; i < n; i += istep)
{
j = i + mmax;
temp_r = w_r * data[j].Re - w_i * data[j].Im;
temp_i = w_r * data[j].Im + w_i * data[j].Re;
data[j].Re = data[i].Re - temp_r;
data[j].Im = data[i].Im - temp_i;
data[i].Re += temp_r;
data[i].Im += temp_i;
}
}
mmax = istep;
}
if(FFTDirection.Reverse == direction)
for(i = 0; i < n; i++)
{
data[i].Re /= (double)n;
data[i].Im /= (double)n;
}
}
public static Complex[,] GetPictureFFT(Complex[,] image, int dim, FFTDirection direction)
{
Complex[] data = new Complex[dim];
for (int i = 0; i < dim; i++)
{
for (int j = 0; j < dim; j++)
{
data[j] = image[j, i];
}
FFT(ref data, direction);
for (int j = 0; j < dim; j++)
{
image[j, i] = data[j];
}
}
data = new Complex[dim];
for (int i = 0; i < dim; i++)
{
for (int j = 0; j < dim; j++)
{
data[j] = image[i, j];
}
FFT(ref data, direction);
for (int j = 0; j < dim; j++)
{
image[i, j] = data[j];
}
}
Complex[,] spectrum = new Complex[dim, dim];
for (int i = 0; i < dim / 2; i++)
{
for (int j = 0; j < dim/2; j++)
{
spectrum[i, j] = image[i + dim / 2, j + dim / 2];
spectrum[i + dim / 2, j + dim / 2] = image[i, j];
spectrum[i + dim / 2, j] = image[i, j + dim / 2];
spectrum[i, j + dim / 2] = image[i + dim / 2, j];
}
}
return spectrum;
}
