怎样将JPEG图片转存成BMP图片？

Question

在引用单元中加入 Jpeg,然后使用如下方法
var
  jpg:TJpegImage;
  bmp:TBitmap;
begin
  jpg:=TJpegImage.Create;
  bmp:=TBitmap.Create;
  jpg.LoadFromFile('1.jpg');  //加载jpeg图片
  bmp.Assign(jpg);           //转换为位图
  bmp.SaveToFile('1.bmp');
  jpg.free;
  bmp.free;
end;
end;

Answer 1

unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls,jpeg;type
    TDrawJPEG = class(TJPEGImage)
    public
      procedure Draw(ACanvas: TCanvas; const Rect: TRect); override;
    end;type
  TForm1 = class(TForm)
    Button1: TButton;
    OpenDialog1: TOpenDialog;
    procedure Button1Click(Sender: TObject);
  private
  public
      procedure LoadJPEGToTBitmap(Filename : string);
  end;var
  Form1: TForm1;implementation{$R *.DFM}procedure TForm1.LoadJPEGToTBitmap(Filename: string);
var
   JPG : TDrawJPEG;
   Bmp:TBitmap;
   R : TRect;
begin
    JPG:=TDrawJPEG.Create;
    Bmp:=TBitmap.Create;
    JPG.LoadFromFile(Filename);
    Bmp.Width:=JPG.Width;
    Bmp.Height:=JPG.Height;
    R.Left:=0;
    R.Top:=0;
    R.Bottom:=JPG.Height;
    R.Right:=JPG.Width;
    JPG.Draw(Bmp.Canvas,R);
    Bmp.SaveToFile('mybmp.bmp');
    JPG.Free;
    Bmp.Free;
end;{ TDrawJPEG }
procedure TDrawJPEG.Draw(ACanvas: TCanvas; const Rect: TRect);
begin
  inherited Draw(ACanvas,Rect);
end;procedure TForm1.Button1Click(Sender: TObject);
begin
    if OpenDialog1.Execute then
        LoadJPEGToTBitmap(Opendialog1.FileName);
end;end.