private static void ConjugateColumn(Complex[,] buffer, int column)
{
for (int j = 0; j < buffer.GetUpperBound(1) + 1; j++)
{
buffer[j, column] = Complex.Conjugate(buffer[j, column]);
}
}
private static void ConjugateRow(Complex[,] buffer, int row)
{
for (int j = 0; j < buffer.GetUpperBound(0) + 1; j++)
{
buffer[row, j] = Complex.Conjugate(buffer[row, j]);
}
}
public double[] MakeDouble(Complex[,] comp)
{
int width = comp.GetUpperBound(0) + 1;
int height = comp.GetUpperBound(1) + 1;
double[] features = new double[width * height];
for (int i = 0; i < width; i++)
{
for (int j = 0; j < height; j++)
{
features[(j * width) + i] = comp[i, j].Im;
}
}
return(features);
}
private static void ScaleColumn(Complex[,] buffer, int column)
{
int size = buffer.GetUpperBound(1) + 1;
for (int j = 0; j < size; j++)
{
buffer[j, column] = buffer[j, column] / size;
}
}
private static void ScaleRow(Complex[,] buffer, int row)
{
int size = buffer.GetUpperBound(0) + 1;
for (int j = 0; j < size; j++)
{
buffer[row, j] = buffer[row, j] / size;
}
}
public static unsafe Bitmap InverseTransform(Complex[,] frequencyDomain, PixelFormat pixelFormat, Bitmap paletteHelper)
{
Complex[,] frequencyDomainCopy = frequencyDomain.Clone() as Complex[, ];
Bitmap output = paletteHelper.Clone(new Rectangle(0, 0, paletteHelper.Width, paletteHelper.Height), paletteHelper.PixelFormat);
BitmapData bData = output.LockBits(new Rectangle(0, 0, output.Width, output.Height), ImageLockMode.ReadWrite, output.PixelFormat);
byte bitsPerPixel = ImageHelper.GetBitsPerPixel(bData.PixelFormat);
byte * scan0 = (byte *)bData.Scan0.ToPointer();
if (bitsPerPixel == 8)
{
for (int i = 0; i < frequencyDomainCopy.GetUpperBound(1) + 1; i++)
{
ConjugateColumn(frequencyDomainCopy, i);
FFTColumn(frequencyDomainCopy, i);
ConjugateColumn(frequencyDomainCopy, i);
ScaleColumn(frequencyDomainCopy, i);
}
for (int i = 0; i < frequencyDomainCopy.GetUpperBound(0) + 1; i++)
{
ConjugateRow(frequencyDomainCopy, i);
FFTRow(frequencyDomainCopy, i);
ConjugateRow(frequencyDomainCopy, i);
ScaleRow(frequencyDomainCopy, i);
}
for (int i = 0; i < bData.Height; ++i)
{
for (int j = 0; j < bData.Width; ++j)
{
byte *data = scan0 + i * bData.Stride + j * bitsPerPixel / 8;
data[0] = ImageHelper.Range((int)Math.Floor(frequencyDomainCopy[i, j].Real), 0, 255);
}
}
}
output.UnlockBits(bData);
return(output);
}
private static void FFTRow(Complex[,] buffer, int row)
{
int bits = (int)Math.Log(buffer.GetUpperBound(0) + 1, 2);
for (int j = 1; j < buffer.GetUpperBound(0) + 1; j++)
{
int swapPos = BitReverse(j, bits);
if (swapPos <= j)
{
continue;
}
var temp = buffer[row, j];
buffer[row, j] = buffer[row, swapPos];
buffer[row, swapPos] = temp;
}
for (int N = 2; N <= buffer.GetUpperBound(0) + 1; N <<= 1)
{
for (int i = 0; i < buffer.GetUpperBound(0) + 1; i += N)
{
for (int k = 0; k < N / 2; k++)
{
int evenIndex = i + k;
int oddIndex = i + k + (N / 2);
var even = buffer[row, evenIndex];
var odd = buffer[row, oddIndex];
double term = -2 * Math.PI * k / (double)N;
Complex exp = new Complex(Math.Cos(term), Math.Sin(term)) * odd;
buffer[row, evenIndex] = even + exp;
buffer[row, oddIndex] = even - exp;
}
}
}
}
public static void SwapQuadrants(Complex [,] frequencyDomain)
{
int size = frequencyDomain.GetUpperBound(0) + 1;
for (int x = 0; x < size / 2; x++)
{
for (int y = 0; y < size / 2; y++)
{
Complex tmp = frequencyDomain[x, y];
frequencyDomain[x, y] = frequencyDomain[x + size / 2, y + size / 2];
frequencyDomain[x + size / 2, y + size / 2] = tmp;
}
}
for (int x = size / 2; x < size; x++)
{
for (int y = 0; y < size / 2; y++)
{
Complex tmp = frequencyDomain[x, y];
frequencyDomain[x, y] = frequencyDomain[x - size / 2, y + size / 2];
frequencyDomain[x - size / 2, y + size / 2] = tmp;
}
}
}