[Из песочницы] Фурье-обработка цифровых изображений
///
/// Copy arrays
///
/// Input array
/// Output array
private static void Copy(Complex[,,] input, Complex[,,] output)
{
int n0 = input.GetLength(0);
int n1 = input.GetLength(1);
int n2 = input.GetLength(2);
int m0 = output.GetLength(0);
int m1 = output.GetLength(1);
int m2 = output.GetLength(2);
int ex0 = Math.Min(n0, m0)/2;
int ex1 = Math.Min(n1, m1)/2;
int ex2 = Math.Min(n2, m2);
Debug.Assert(n2 == m2);
for (int k = 0; k < ex2; k++)
{
for (int i = 0; i <= ex0; i++)
{
for (int j = 0; j <= ex1; j++)
{
int ni = n0 - i - 1;
int nj = n1 - j - 1;
int mi = m0 - i - 1;
int mj = m1 - j - 1;
output[i, j, k] = input[i, j, k];
output[mi, j, k] = input[ni, j, k];
output[i, mj, k] = input[i, nj, k];
output[mi, mj, k] = input[ni, nj, k];
}
}
}
}
///
/// Resize bitmap with the Fastest Fourier Transform
///
/// Resized bitmap
public Bitmap Stretch(Bitmap bitmap)
{
using (var image = new Image(bitmap))
{
int length = image.Data.Length;
int n0 = image.Data.GetLength(0);
int n1 = image.Data.GetLength(1);
int n2 = image.Data.GetLength(2);
var doubles = new double[length];
Buffer.BlockCopy(image.Data, 0, doubles, 0, length*sizeof (double));
double power = Math.Sqrt(doubles.Average(x => x*x));
var input = new fftw_complexarray(doubles.Select(x => new Complex(x, 0)).ToArray());
var output = new fftw_complexarray(length);
fftw_plan.dft_3d(n0, n1, n2, input, output,
fftw_direction.Forward,
fftw_flags.Estimate).Execute();
Complex[] complex = output.GetData_Complex();
using (var image2 = new Image(_newSize))
{
int length2 = image2.Data.Length;
int m0 = image2.Data.GetLength(0);
int m1 = image2.Data.GetLength(1);
int m2 = image2.Data.GetLength(2);
var complex2 = new Complex[length2];
var data = new Complex[n0, n1, n2];
var data2 = new Complex[m0, m1, m2];
var buffer = new double[length*2];
GCHandle complexHandle = GCHandle.Alloc(complex, GCHandleType.Pinned);
GCHandle dataHandle = GCHandle.Alloc(data, GCHandleType.Pinned);
IntPtr complexPtr = complexHandle.AddrOfPinnedObject();
IntPtr dataPtr = dataHandle.AddrOfPinnedObject();
Marshal.Copy(complexPtr, buffer, 0, buffer.Length);
Marshal.Copy(buffer, 0, dataPtr, buffer.Length);
complexHandle.Free();
dataHandle.Free();
Copy(data, data2);
buffer = new double[length2*2];
complexHandle = GCHandle.Alloc(complex2, GCHandleType.Pinned);
dataHandle = GCHandle.Alloc(data2, GCHandleType.Pinned);
complexPtr = complexHandle.AddrOfPinnedObject();
dataPtr = dataHandle.AddrOfPinnedObject();
Marshal.Copy(dataPtr, buffer, 0, buffer.Length);
Marshal.Copy(buffer, 0, complexPtr, buffer.Length);
complexHandle.Free();
dataHandle.Free();
var input2 = new fftw_complexarray(complex2);
var output2 = new fftw_complexarray(length2);
fftw_plan.dft_3d(m0, m1, m2, input2, output2,
fftw_direction.Backward,
fftw_flags.Estimate).Execute();
double[] array2 = output2.GetData_Complex().Select(x => x.Magnitude).ToArray();
double power2 = Math.Sqrt(array2.Average(x => x*x));
double[] doubles2 = array2.Select(x => x*power/power2).ToArray();
Buffer.BlockCopy(doubles2, 0, image2.Data, 0, length2*sizeof (double));
return image2.Bitmap;
}
}
}
