var   ScreenDC: HDC;
   canvas:Tcanvas;
 begin 
  ScreenDC:=GetDC(0);  
 Canvas:=TCanvas.Create(); 
  canvas.Handle:=ScreenDC; 
  Width:=Screen.Width;   
Height:=Screen.Height;   Img1.Canvas.CopyRect(Rect(0,0,Img1.Width,Img1.Height),   canvas,Rect(0,0,Screen.Width,Screen.Height));   Releasedc(0,ScreenDC);  
 Canvas.Free;
 end;