Обучалки

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls, StdCtrls, jpeg;
 
...
 
procedure TForm1.Button1Click(Sender: TObject);
begin
  Image1.Picture.LoadFromFile('c:/windows.jpg');
end;

procedure TForm1.Button1Click(Sender: TObject);
var
DeskTopDC: HDc;
DeskTopCanvas: TCanvas;
DeskTopRect: TRect;
 
 
begin
DeskTopDC := GetWindowDC(GetDeskTopWindow);
DeskTopCanvas := TCanvas.Create;
DeskTopCanvas.Handle := DeskTopDC;
 
 
DeskTopRect := Rect(0,0,Screen.Width,Screen.Height);
 
 
Image1.Canvas.CopyRect(DeskTopRect,DeskTopCanvas,DeskTopRect);
 
 
ReleaseDC(GetDeskTopWindow,DeskTopDC);
 
end;

  procedure TForm1.FormCreate(Sender: TObject);
  begin
     Brush.Style:=bsClear;
  end;