如何用delphi实现抓图功能？

Question

拷贝的一段程序，参考参考
procedure TForm1.Button1Click(Sender: TObject);
var
  Fullscreen:Tbitmap;
  FullscreenCanvas:TCanvas;
  dc:HDC;
  myJpeg:TJpegImage;
  begin
    Fullscreen := TBitmap.Create; // create a bimap to save picture
    myJpeg := TJpegImage.Create;
    Fullscreen.Width := screen.width;
    Fullscreen.Height := screen.Height;
    DC := GetDC (0); // get screen dc
    FullscreenCanvas := TCanvas.Create; //create screen canvas
    FullscreenCanvas.Handle := DC;
    Fullscreen.Canvas.CopyRect (Rect (0, 0, screen.Width, screen.Height), fullscreenCanvas,Rect (0, 0, Screen.Width, Screen.Height));
    FullscreenCanvas.Free; //free screencanvas
    ReleaseDC (0, DC);
//*******************************image1.picture.Bitmap:=fullscreen;//哈哈，拿到屏幕了！
    image1.Width:=fullscreen.Width;
    image1.Height:=fullscreen.Height;
    image1.Picture.bitmap:=fullscreen;
    myJpeg.Assign(Image1.Picture.Bitmap);
    myJpeg.CompressionQuality := 50;
    myJpeg.Compress;
    myJpeg.SaveToFile('1.jpg');
    myJpeg.Free;
    fullscreen.free; //free bitmap
end;