用多媒体库 Bass.dll 播放 mp3 [9] 绘制波形图

本例效果图:

---

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