c# 频谱瀑布图

要绘制C#频谱瀑布图，可以使用.NET的Windows.Forms图形库和NAudio音频库。以下是一个简单的示例代码：

using System;
using System.Windows.Forms;
using NAudio.Wave;
using System.Drawing;

namespace SpectrumWaterfall
{
    public partial class MainForm : Form
    {
        private WaveIn waveIn;
        private BufferedWaveProvider bufferedWaveProvider;
        private Bitmap waterfallBitmap;
        private Graphics waterfallGraphics;
        private int waterfallWidth;
        private int waterfallHeight;
        private int[] waterfallData;
        private int waterfallIndex;

        public MainForm()
        {
            InitializeComponent();

            // 初始化瀑布图
            waterfallWidth = pictureBox.Width;
            waterfallHeight = pictureBox.Height;
            waterfallBitmap = new Bitmap(waterfallWidth, waterfallHeight);
            waterfallGraphics = Graphics.FromImage(waterfallBitmap);
            waterfallData = new int[waterfallWidth];

            // 初始化音频输入
            waveIn = new WaveIn();
            waveIn.WaveFormat = new WaveFormat(44100, 16, 1);
            waveIn.DataAvailable += WaveIn_DataAvailable;
            bufferedWaveProvider = new BufferedWaveProvider(waveIn.WaveFormat);
            bufferedWaveProvider.BufferLength = waveIn.WaveFormat.AverageBytesPerSecond * 2;
            bufferedWaveProvider.DiscardOnBufferOverflow = true;
            waveIn.StartRecording();
        }

        private void WaveIn_DataAvailable(object sender, WaveInEventArgs e)
        {
            bufferedWaveProvider.AddSamples(e.Buffer, 0, e.BytesRecorded);

            // 取得FFT结果
            var fft = new FFT();
            var fftBuffer = new float[bufferedWaveProvider.BufferLength / 2];
            int bytesPerSample = waveIn.WaveFormat.BitsPerSample / 8;
            int samplesProcessed = bufferedWaveProvider.BufferedBytes / bytesPerSample;
            for (int i = 0; i < samplesProcessed; i++)
            {
                // 从缓冲区获取样本
                byte[] sampleBuffer = new byte[bytesPerSample];
                bufferedWaveProvider.Read(sampleBuffer, 0, bytesPerSample);

                // 将样本转换为浮点数
                float sampleValue = 0;
                if (waveIn.WaveFormat.BitsPerSample == 16)
                {
                    short sample = BitConverter.ToInt16(sampleBuffer, 0);
                    sampleValue = sample / 32768f;
                }
                else if (waveIn.WaveFormat.BitsPerSample == 24)
                {
                    int sample = BitConverter.ToInt32(sampleBuffer, 0);
                    sampleValue = sample / 8388608f;
                }

                // 添加样本到FFT缓冲区
                fftBuffer[i] = sampleValue;
            }
            var fftResult = fft.Process(fftBuffer);

            // 将FFT结果绘制到瀑布图
            for (int i = 0; i < fftResult.Length; i++)
            {
                int value = (int)(Math.Log10(fftResult[i]) * 20) + waterfallHeight / 2;
                if (value < 0) value = 0;
                if (value >= waterfallHeight) value = waterfallHeight - 1;
                waterfallData[waterfallIndex + i] = value;
            }
            waterfallIndex += fftResult.Length;
            if (waterfallIndex >= waterfallWidth)
            {
                waterfallIndex = 0;
                waterfallGraphics.Clear(Color.Black);
            }
            for (int x = 0; x < waterfallWidth; x++)
            {
                int y = waterfallData[(waterfallIndex + x) % waterfallWidth];
                waterfallBitmap.SetPixel(x, y, Color.White);
            }

            // 将瀑布图显示到PictureBox控件
            pictureBox.Image = waterfallBitmap;
        }
    }
}

该示例代码使用NAudio库来获取音频输入并对其进行FFT处理，然后将FFT结果绘制到瀑布图上。瀑布图通过一个Bitmap对象来绘制，并显示在一个PictureBox控件上。注意，该示例代码只是一个简单的示例，实际应用中可能需要进行优化和调整。