delphi – 加载Jpg / Gif / Bitmap并转换为Bitmap

我必须从 XML文件加载一个图像. XML文件中没有关于图像是JPG / GIF / BMP的信息.加载图像后,我需要将其转换为Bitmap.

有没有人知道如何将图像转换为Bitmap而不知道实际的文件格式？我正在使用Delphi 2007/2009

谢谢.

解决方法

Delphi 2009内置支持JPEG,BMP,GIF和PNG.

对于早期版本的Delphi,您可能需要找到PNG和GIF的第三方实现,但在Delphi 2009中,您只需将Jpeg,pngimage和GIFImg单元添加到您的uses子句中即可.

如果文件具有扩展名,则可以使用以下代码,如其他人所述,TPicture.LoadFromFile查看继承的类注册的扩展名,以确定要加载的映像.

uses
  Graphics,Jpeg,pngimage,GIFImg;

procedure TForm1.Button1Click(Sender: TObject);
var
  Picture: TPicture;
  Bitmap: TBitmap;
begin
  Picture := TPicture.Create;
  try
    Picture.LoadFromFile('C:\imagedata.dat');
    Bitmap := TBitmap.Create;
    try
      Bitmap.Width := Picture.Width;
      Bitmap.Height := Picture.Height;
      Bitmap.Canvas.Draw(0,Picture.Graphic);
      Bitmap.SavetoFile('C:\test.bmp');
    finally
      Bitmap.Free;
    end;
  finally
    Picture.Free;
  end;
end;

如果文件扩展名不知道,一个方法是查看前几个字节来确定图像类型.

procedure Detectimage(const InputFileName: string; BM: TBitmap);
var
  FS: TFileStream;
  FirstBytes: AnsiString;
  Graphic: TGraphic;
begin
  Graphic := nil;
  FS := TFileStream.Create(InputFileName,fmOpenRead);
  try
    SetLength(FirstBytes,8);
    FS.Read(FirstBytes[1],8);
    if copy(FirstBytes,1,2) = 'BM' then
    begin
      Graphic := TBitmap.Create;
    end else
    if FirstBytes = #137'PNG'#13#10#26#10 then
    begin
      Graphic := TPngImage.Create;
    end else
    if copy(FirstBytes,3) =  'GIF' then
    begin
      Graphic := TGIFImage.Create;
    end else
    if copy(FirstBytes,2) = #$FF#$D8 then
    begin
      Graphic := TJPEGImage.Create;
    end;
    if Assigned(Graphic) then
    begin
      try
        FS.Seek(0,soFromBeginning);
        Graphic.LoadFromStream(FS);
        BM.Assign(Graphic);
      except
      end;
      Graphic.Free;
    end;
  finally
    FS.Free;
  end;
end;