用多媒体库 Bass.dll 播放 mp3 [9] - 绘制波形图

本例效果图:

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代码文件:

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unit Unit1;interfaceusesWindows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,Dialogs, StdCtrls, ExtCtrls, ComCtrls;typeTForm1 = class(TForm)OpenDialog1: TOpenDialog;PaintBox1: TPaintBox;Button1: TButton;Button2: TButton;Button3: TButton;ColorBox1: TColorBox;ColorBox2: TColorBox;procedure FormCreate(Sender: TObject);procedure Button1Click(Sender: TObject);procedure Button2Click(Sender: TObject);procedure Button3Click(Sender: TObject);procedure ColorBox1Change(Sender: TObject);procedure ColorBox2Change(Sender: TObject);procedure FormDestroy(Sender: TObject);procedure PaintBox1Paint(Sender: TObject);privateprocedure Draw;end;varForm1: TForm1;implementation{$R *.dfm}uses Bass;varhs: HSTREAM;  {流句柄}Data: array of Cardinal;bit: TBitmap;procedure TForm1.FormCreate(Sender: TObject);
beginbit := TBitmap.Create;PaintBox1.Align := alTop;ColorBox1.Selected := clBlack;ColorBox2.Selected := clLime;if HiWord(BASS_GetVersion) <> BASSVERSION thenMessageBox(0, '"Bass.dll" 文件版本不合适! ', nil, MB_ICONERROR);if not BASS_Init(-1, 44100, 0, 0, nil) then ShowMessage('初始化错误');
end;{打开}
procedure TForm1.Button1Click(Sender: TObject);
varMp3Path: AnsiString;i: Cardinal;time: Double;hs2: HSTREAM;
beginBASS_StreamFree(hs);OpenDialog1.Filter := 'Mp3 文件(*.mp3)|*.mp3|Wav 文件(*.wav)|*wav';if OpenDialog1.Execute thenMp3Path := AnsiString(OpenDialog1.FileName);hs := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, 0);if hs < BASS_ERROR_ENDED thenText := '打开失败'else beginText := string(Mp3Path);bit.Free;bit := TBitmap.Create;PaintBox1.Repaint;{下面几行不好理解}{重新建立文件流 hs2, 最后的参数是: BASS_STREAM_DECODE, 这样可以提前读取波形数据}hs2 := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, BASS_STREAM_DECODE);{用 BASS_ChannelGetLevel 获取峰值时, 是以 20ms 为一个单位的; 先获取总时间}time := BASS_ChannelBytes2Seconds(hs2, BASS_ChannelGetLength(hs, BASS_POS_BYTE));{time * 1000 div 20 + 1 是可以获取的总的峰值数据, 也是数组需要的大小}SetLength(Data, Trunc(time * 50 + 1));{遍历峰值数据填充数组}for i := 0 to Length(Data) - 1 do Data[i] := BASS_ChannelGetLevel(hs2);{hs2 此时已完成使命, 释放它}BASS_StreamFree(hs2);{调用绘制过程}Draw;end;
end;{播放}
procedure TForm1.Button2Click(Sender: TObject);
beginBASS_ChannelPlay(hs, False);
end;{暂停}
procedure TForm1.Button3Click(Sender: TObject);
beginBASS_ChannelPause(hs);
end;{背景色}
procedure TForm1.ColorBox1Change(Sender: TObject);
beginDraw;
end;{前景色}
procedure TForm1.ColorBox2Change(Sender: TObject);
beginDraw;
end;procedure TForm1.FormDestroy(Sender: TObject);
beginBASS_Free;bit.Free;
end;{刷新}
procedure TForm1.PaintBox1Paint(Sender: TObject);
beginPaintBox1.Canvas.StretchDraw(Bounds(0, 0, PaintBox1.Width, PaintBox1.Height), bit);
end;{绘制波形图}
procedure TForm1.Draw;
vari,ch: Integer;L,R: SmallInt;
beginbit.Width := Length(Data);bit.Height := PaintBox1.Height;ch := bit.Height div 2;bit.Canvas.Brush.Color := ColorBox1.Selected;bit.Canvas.FillRect(Bounds(0, 0, bit.Width, bit.Height));bit.Canvas.Pen.Color := ColorBox2.Selected;for i := 0 to Length(Data) - 1 dobeginL := LoWord(Data[i]);R := HiWord(Data[i]);bit.Canvas.MoveTo(i, ch - Trunc(L/32768*ch));bit.Canvas.LineTo(i, ch + Trunc(R/32768*ch));end;PaintBox1.Repaint;
end;end.

窗体文件:

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object Form1: TForm1Left = 222Top = 114Caption = 'Form1'ClientHeight = 173ClientWidth = 504Color = clBtnFaceFont.Charset = DEFAULT_CHARSETFont.Color = clWindowTextFont.Height = -11Font.Name = 'Tahoma'Font.Style = []OldCreateOrder = FalsePosition = poDesignedOnCreate = FormCreateOnDestroy = FormDestroyPixelsPerInch = 96TextHeight = 13object PaintBox1: TPaintBoxLeft = 40Top = 0Width = 105Height = 131OnPaint = PaintBox1Paintendobject Button1: TButtonLeft = 8Top = 137Width = 75Height = 25Caption = #25171#24320TabOrder = 0OnClick = Button1Clickendobject Button2: TButtonLeft = 89Top = 137Width = 75Height = 25Caption = #25773#25918TabOrder = 1OnClick = Button2Clickendobject Button3: TButtonLeft = 170Top = 137Width = 75Height = 25Caption = #26242#20572TabOrder = 2OnClick = Button3Clickendobject ColorBox1: TColorBoxLeft = 315Top = 139Width = 85Height = 22ItemHeight = 16TabOrder = 3OnChange = ColorBox1Changeendobject ColorBox2: TColorBoxLeft = 406Top = 139Width = 90Height = 22ItemHeight = 16TabOrder = 4OnChange = ColorBox2Changeendobject OpenDialog1: TOpenDialogLeft = 192Top = 32end
end