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:

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls, ExtCtrls, ComCtrls;



type

  TForm1 = 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);

  private

    procedure Draw;

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses Bass;



var

  hs: HSTREAM;  {流句柄}

  Data: array of Cardinal;

  bit: TBitmap;



procedure TForm1.FormCreate(Sender: TObject);

begin

  bit := TBitmap.Create;

  PaintBox1.Align := alTop;

  ColorBox1.Selected := clBlack;

  ColorBox2.Selected := clLime;



  if HiWord(BASS_GetVersion) <> BASSVERSION then

    MessageBox(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);

var

  Mp3Path: AnsiString;

  i: Cardinal;

  time: Double;

  hs2: HSTREAM;

begin

  BASS_StreamFree(hs);



  OpenDialog1.Filter := 'Mp3 文件(*.mp3)|*.mp3|Wav 文件(*.wav)|*wav';

  if OpenDialog1.Execute then

    Mp3Path := AnsiString(OpenDialog1.FileName);



  hs := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, 0);

  if hs < BASS_ERROR_ENDED then

    Text := '打开失败'

  else begin

    Text := 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);

begin

  BASS_ChannelPlay(hs, False);

end;



{暂停}

procedure TForm1.Button3Click(Sender: TObject);

begin

  BASS_ChannelPause(hs);

end;



{背景色}

procedure TForm1.ColorBox1Change(Sender: TObject);

begin

  Draw;

end;



{前景色}

procedure TForm1.ColorBox2Change(Sender: TObject);

begin

  Draw;

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  BASS_Free;

  bit.Free;

end;



{刷新}

procedure TForm1.PaintBox1Paint(Sender: TObject);

begin

  PaintBox1.Canvas.StretchDraw(Bounds(0, 0, PaintBox1.Width, PaintBox1.Height), bit);

end;



{绘制波形图}

procedure TForm1.Draw;

var

  i,ch: Integer;

  L,R: SmallInt;

begin

  bit.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 do

  begin

    L := 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:

---

object Form1: TForm1

  Left = 222

  Top = 114

  Caption = 'Form1'

  ClientHeight = 173

  ClientWidth = 504

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesigned

  OnCreate = FormCreate

  OnDestroy = FormDestroy

  PixelsPerInch = 96

  TextHeight = 13

  object PaintBox1: TPaintBox

    Left = 40

    Top = 0

    Width = 105

    Height = 131

    OnPaint = PaintBox1Paint

  end

  object Button1: TButton

    Left = 8

    Top = 137

    Width = 75

    Height = 25

    Caption = #25171#24320

    TabOrder = 0

    OnClick = Button1Click

  end

  object Button2: TButton

    Left = 89

    Top = 137

    Width = 75

    Height = 25

    Caption = #25773#25918

    TabOrder = 1

    OnClick = Button2Click

  end

  object Button3: TButton

    Left = 170

    Top = 137

    Width = 75

    Height = 25

    Caption = #26242#20572

    TabOrder = 2

    OnClick = Button3Click

  end

  object ColorBox1: TColorBox

    Left = 315

    Top = 139

    Width = 85

    Height = 22

    ItemHeight = 16

    TabOrder = 3

    OnChange = ColorBox1Change

  end

  object ColorBox2: TColorBox

    Left = 406

    Top = 139

    Width = 90

    Height = 22

    ItemHeight = 16

    TabOrder = 4

    OnChange = ColorBox2Change

  end

  object OpenDialog1: TOpenDialog

    Left = 192

    Top = 32

  end

end