forma buton ekle yeter...
procedure TForm1.Button1Click(Sender: TObject);
var
hh,hdev:hdc;
bm:hbitmap;
a,h,w:integer;
begin
hh:=CreateCompatibleDC(GetDC(handle));
bm:=CreateCompatibleBitmap(GetDC(handle),width,height);
SelectObject(hh,bm);
form1.Hide;
hdev:=GetWindowDC(GetDesktopWindow);
BitBlt(hh,0,0,width,height,hdev,form1.Left,form1.Top,SRCCOPY);
Randomize;
for a:=1 to 500000 do
begin
w:=random(width);
h:=random(height);
SetPixel(hdev,left+w,top+h,GetPixel(hh,w,h));
end;
Form1.Show;
end;