用多媒體庫 Bass.dll 播放 mp3 [12] - 繪制動態頻譜 FFT

本例效果圖:

　　代碼文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls, ExtCtrls, ComCtrls;
type
　TForm1 = class(TForm)
　　OpenDialog1: TOpenDialog;
　　Timer1: TTimer;
　　PaintBox1: TPaintBox;
　　Button1: TButton;
　　Button2: TButton;
　　Button3: TButton;
　　procedure FormCreate(Sender: TObject);
　　procedure Button1Click(Sender: TObject);
　　procedure Button2Click(Sender: TObject);
　　procedure Button3Click(Sender: TObject);
　　procedure FormDestroy(Sender: TObject);
　　procedure PaintBox1Paint(Sender: TObject);
　　procedure Timer1Timer(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses Bass;
var
　hs: HSTREAM;　{流句柄}
　FFTData: array[0..512] of Single;
　bit: TBitmap;
　FFTPeacks　: array [0..128] of Integer;
　FFTFallOff : array [0..128] of Integer;
procedure TForm1.FormCreate(Sender: TObject);
begin
　Timer1.Enabled := False;
　Timer1.Interval := 30;
　bit := TBitmap.Create;
　PaintBox1.Align := alTop;
　if HiWord(BASS_GetVersion) <> BASSVERSION then
　　MessageBox(0, '"Bass.dll" 文件版本不合適! ', nil, MB_ICONERROR);
　if not BASS_Init(-1, 44100, 0, 0, nil) then ShowMessage('初始化錯誤');
end;
{打開}
procedure TForm1.Button1Click(Sender: TObject);
var
　Mp3Path: AnsiString;
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 := '打開失敗'
　else begin
　　Text := string(Mp3Path);
　　bit.Free;
　　bit := TBitmap.Create;
　　PaintBox1.Repaint;
　end;
end;
{播放}
procedure TForm1.Button2Click(Sender: TObject);
begin
　Timer1.Enabled := True;
　BASS_ChannelPlay(hs, False);
end;
{暫停}
procedure TForm1.Button3Click(Sender: TObject);
begin
　Timer1.Enabled := False;
　BASS_ChannelPause(hs);
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;
{繪制 FFT}
procedure TForm1.Timer1Timer(Sender: TObject);
const
　w = 8;
var
　i,di: Integer;
begin
　if BASS_ChannelIsActive(hs) <> BASS_ACTIVE_PLAYING then Exit;
　BASS_ChannelGetData(hs, @FFTData, BASS_DATA_FFT1024);
　bit.Width := PaintBox1.Width;
　bit.Height := PaintBox1.Height;
　bit.Canvas.Brush.Color := clBlack;
　bit.Canvas.FillRect(Rect(0, 0, bit.Width, bit.Height));
　bit.Canvas.Pen.Color := clLime;
　for i := 0 to Length(FFTData) - 1 do
　begin
　　di := Trunc(Abs(FFTData[i]) * 500);
　　if di > bit.Height then di := bit.Height;
　　if di >= FFTPeacks[i] then FFTPeacks[i] := di else FFTPeacks[i] := FFTPeacks[i] - 1;
　　if di >= FFTFallOff[i] then FFTFallOff[i] := di else FFTFallOff[i] := FFTFallOff[i] - 3;
　　if (bit.Height - FFTPeacks[i]) > bit.Height then FFTPeacks[i] := 0;
　　if (bit.Height - FFTFallOff[i]) > bit.Height then FFTFallOff[i] := 0;
//　　bit.Canvas.MoveTo(i, bit.Height);
//　　bit.Canvas.LineTo(i, bit.Height - FFTFallOff[i]);
//　　bit.Canvas.Pixels[i, bit.Height - FFTPeacks[i]] := bit.Canvas.Pen.Color;
　　bit.Canvas.Pen.Color := bit.Canvas.Pen.Color;
　　bit.Canvas.MoveTo(i * (w + 1), bit.Height - FFTPeacks[i]);
　　bit.Canvas.LineTo(i * (w + 1) + w, bit.Height - FFTPeacks[i]);
　　bit.Canvas.Pen.Color := bit.Canvas.Pen.Color;
　　bit.Canvas.Brush.Color := bit.Canvas.Pen.Color;
　　bit.Canvas.Rectangle(i * (w + 1), bit.Height - FFTFallOff[i], i * (w + 1) + w, bit.Height);
　end;
　BitBlt(PaintBox1.Canvas.Handle, 0, 0, PaintBox1.Width, PaintBox1.Height, bit.Canvas.Handle, 0, 0, SRCCOPY);
end;
end.窗體文件:object Form1: TForm1
　Left = 222
　Top = 114
　Caption = 'Form1'
　ClIEntHeight = 154
　ClIEntWidth = 476
　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 = 16
　　Top = 0
　　Width = 105
　　Height = 105
　　OnPaint = PaintBox1Paint
　end
　object Button1: TButton
　　Left = 109
　　Top = 117
　　Width = 75
　　Height = 25
　　Caption = #25171#24320
　　TabOrder = 0
　　OnClick = Button1Click
　end
　object Button2: TButton
　　Left = 206
　　Top = 117
　　Width = 75
　　Height = 25
　　Caption = #25773#25918
　　TabOrder = 1
　　OnClick = Button2Click
　end
　object Button3: TButton
　　Left = 303
　　Top = 117
　　Width = 75
　　Height = 25
　　Caption = #26242#20572
　　TabOrder = 2
　　OnClick = Button3Click
　end
　object OpenDialog1: TOpenDialog
　　Left = 128
　　Top = 24
　end
　object Timer1: TTimer
　　OnTimer = Timer1Timer
　　Left = 128
　　Top = 72
　end