procedure TForm1.Button1Click(Sender: TObject);
var
rect1,rect2:trect;
bm:tbitmap;
begin
bm:=tbitmap.Create;
openpicturedialog1.Execute;
bm.LoadFromFile(openpicturedialog1.filename);
with rect1 do
begin
left:=0;
top:=0;
right:=bm.width;
bottom:=bm.height;
end;
with rect2 do
begin
left:=0;
top:=0;
right:=bm.width*2;//放大倍数为2
bottom:=bm.height*2;//放大倍数为2
end;