C# 实时声音频率图绘制

采集PCM音频数据

音频原来自麦克风

音频源来自录音文件

处理PCM音频数据

使用 FftSharp.FFT 将PCM数据进行傅里叶变换

安装FftSharp框架

在Nuget包管理器中搜索FftSharp并安装

傅里叶变换

将采集到的PCM数据进行傅里叶变换

      // 傅里叶变换System.Numerics.Complex[] spectrum = FftSharp.FFT.Forward(audio);double[] ys = FftSharp.FFT.Magnitude(spectrum);

绘制频率图

采用自定义控件的方式来绘制频率图，核心代码如下：

        protected override void OnRender(DrawingContext drawingContext){// 渲染数据DrawFrequency(drawingContext, this.ActualWidth, this.ActualHeight);}private void DrawFrequency(DrawingContext drawingContext, double imageWidth, double imageHeight){double width = imageWidth - MarginLeft - 1;double height = imageHeight - MarginBottom - 1;var itemWidth = width / 4;var itemHeight = height / 4;drawingContext.DrawRectangle(this.Background, null, new Rect(0, 0, imageWidth, imageHeight));// 画方框drawingContext.DrawRect(this.Foreground, 1 + MarginLeft, 1, width, height);// 画竖线for (int i = 1; i < 4; i++){var left = i * itemWidth;drawingContext.DrawLine(this.Foreground, left + MarginLeft, 0, left + MarginLeft, height);// 画文本var freq = MaxFrequency * (i * 0.25);drawingContext.DrawText(FormatUtil.Frequency(freq), this.TextBrush, left + MarginLeft, height + MarginBottom / 2 + 2, 13);}drawingContext.DrawText(FormatUtil.Frequency(0), this.TextBrush, MarginLeft + 10, height + MarginBottom / 2 + 2, 13);drawingContext.DrawText(FormatUtil.Frequency(MaxFrequency), this.TextBrush, width + MarginLeft - 16, height + MarginBottom / 2 + 2, 13);// 画横线for (int i = 1; i < 4; i++){var top = i * itemHeight;drawingContext.DrawLine(this.Foreground, MarginLeft + 1, top, 10 + MarginLeft, top);// 画文本drawingContext.DrawText(Convert.ToString(20 - i * 5), this.TextBrush, MarginLeft / 2, top, 13);}// 画折线if (dataPoints.Count > 0){DrawPointPath(drawingContext, width, height);}}private void DrawPointPath(DrawingContext drawingContext, double width, double height){var itemHeight = height / 20;var itemWidth = width / dataPoints.Count;var amplitude = (mMaxVolume - mMinVolume) * 2;// 开始绘制路径StreamGeometry geometry = new StreamGeometry();using (StreamGeometryContext context = geometry.Open()){// 将路径移动到第一个数据点var x = (1 - dataPoints[0] / amplitude) * 20;context.BeginFigure(new Point(MarginLeft + 1, x * itemHeight), false, false);// 添加线段连接每个数据点for (int i = 1; i < dataPoints.Count; i++){x = (1 - dataPoints[i] / amplitude) * 20;context.LineTo(new Point(i * itemWidth + MarginLeft + 1, x * itemHeight), true, false);}}// 绘制路径drawingContext.DrawGeometry(null, pen, geometry);}

其他拓展类

FormatUtil

internal class FormatUtil{public static string Frequency(double freq){if (freq < 1000){return string.Format("{0}Hz", (int)freq);}else{var value = Math.Floor(freq / 1000);return string.Format("{0}kHz", value);}}}

DrawingContextExt

public static class DrawingContextExt
{public static void DrawRect(this DrawingContext drawingContext, Brush color, double x, double y, double w, double h){drawingContext.DrawRectangle(null, new Pen(color, 1), new System.Windows.Rect(x, y, w, h));}public static void DrawLine(this DrawingContext drawingContext, Brush color, double x, double y, double x2, double y2){drawingContext.DrawLine(new Pen(color, 1), new Point(x, y), new Point(x2, y2));}public static void FillEllipse(this DrawingContext drawingContext, Brush brush, double x, double y, double w, double h){var radiusX = w / 2;var radiusY = h / 2;drawingContext.DrawEllipse(brush, null, new Point(x - radiusX, y - radiusY), radiusX, radiusY);}public static void DrawText(this DrawingContext drawingContext, string data, Brush brush, double x, double y, double emSize = 10){// 创建FormattedText对象以设置文字的样式、位置和对齐方式FormattedText formattedText = new FormattedText(data,System.Globalization.CultureInfo.CurrentCulture,FlowDirection.LeftToRight,new Typeface("Arial"),emSize, brush);// 设置文字在 (50, 50) 的位置水平和垂直居中// 计算绘制点的坐标，使文本居中绘制Point drawPoint = new Point(x - formattedText.Width / 2, y - formattedText.Height / 2);// 绘制文字drawingContext.DrawText(formattedText, drawPoint);}
}