/// <summary>
/// 用倒谱获得频谱包络
/// </summary>
/// <param name="data"></param>
/// <returns></returns>
private static double[] GetEnvelopeFD(double[] data)
{
int n = data.Length;
double[] data1 = new double[n];
double[] data1i = new double[n];
for (int i = 0; i < n; i++)
{
data1[i] = Math.Log(data[i]);
}
for (int i = 0; i < n; i++)
{
data1i[i] = 0;
}
TWFFT.FFT(data1, data1i);
double therehold = 100;
double[] data2 = new double[n];
double[] data2i = new double[n];
// 低通滤波
for (int i = 0; i < n; i++)
{
if (i < therehold || i > n - therehold)
{
data2[i] = data1[i];
data2i[i] = data1i[i];
}
else
{
data2[i] = 0;
data2i[i] = 0;
}
}
//for (int i = 0; i < n; i++) data2i[i] = 0;
TWFFT.IFFT(data2, data2i);
var res = FToneAnalysis.MiddleFilter(data2, 3);
for (int i = 0; i < n; i++)
{
res[i] = Math.Pow(Math.E, res[i]);
}
return(res);
}
public static Image getFFTImage(int[] data)
{
int w = 2000;
int h = 1000;
Bitmap bitmap = new Bitmap(w, h);
Graphics g = Graphics.FromImage(bitmap);
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
//draw fft
int n = 4096;
double[] datas = new double[n];
double[] datas2 = new double[n];
double[] datamod = new double[n];
//if (data.Length <= n) return null;
for (int i = 0; i < n; i++)
{
datas2[i] = 0;
if (i > data.Length - 1)
{
datas[i] = 0;
}
else
{
datas[i] = data[i];
}
}
TWFFT.FFT(datas, datas2);
for (int i = 0; i < n; i++)
{
datamod[i] = Math.Sqrt(datas[i] * datas[i] + datas2[i] * datas2[i]);
}
int time = 2;
for (int i = 1; i < n / time; i++)
{
g.DrawLine(new Pen(Color.Black, 1),
new Point((int)((double)(i - 1) / n * time * bitmap.Width), (int)(h - datamod[i - 1] / w)),
new Point((int)((double)i / n * time * bitmap.Width), (int)(h - datamod[i] / w)));
}
double[] datad = new double[n];
double[] datad2 = new double[n];
for (int i = 0; i < n; i++)
{
datad2[i] = 0;
}
for (int i = 0; i < n; i++)
{
datad[i] = Math.Log(datamod[i]);
}
for (int i = 1; i < n / time; i++)
{
g.DrawLine(new Pen(Color.Red, 1),
new Point((int)((double)(i - 1) / n * time * bitmap.Width), (int)(h - datad[i - 1] * 50)),
new Point((int)((double)i / n * time * bitmap.Width), (int)(h - datad[i] * 50)));
}
TWFFT.FFT(datad, datad2);
for (int i = 0; i < n; i++)
{
datamod[i] = Math.Log(Math.Sqrt(datad[i] * datad[i] + datad2[i] * datad2[i]));
}
double therehold = 100;
double[] rdata = new double[n];
double[] rdata2 = new double[n];
for (int i = 0; i < n; i++)
{
if (i < therehold || i > n - therehold)
{
rdata[i] = datad[i];
}
else
{
rdata[i] = 0;
}
}
for (int i = 0; i < n; i++)
{
rdata2[i] = datad2[i];
}
TWFFT.IFFT(rdata, rdata2);
for (int i = 1; i < n / time; i++)
{
g.DrawLine(new Pen(Color.Blue, 1),
new Point((int)((double)(i - 1) / n * time * bitmap.Width), (int)(h - rdata[i - 1] * 50)),
new Point((int)((double)i / n * time * bitmap.Width), (int)(h - rdata[i] * 50)));
}
return(bitmap);
}