用下面的程序取屏幕的一小块为什么得到的是一张空白图？ ( 积分: 22 )

var
c: tcanvas;
bmp:TBitmap;
begin
c:=TCanvas.Create;
c.Handle:=GetDC(0);
bmp:=TBitmap.Create;
bmp.Canvas.CopyRect(Rect(0,0,100,100),c,Rect(0,0,100,100));
bmp.SaveToFile('C:/1.bmp');
bmp.Free;

bmp:=TBitmap.Create;
bmp.width := 100;
bmp.height := 100;

procedure TForm1.Button1Click(Sender: TObject);
var
c: tcanvas;
bmp:TBitmap;
begin
c:=TCanvas.Create;
c.Handle:=GetDC(0);
bmp:=TBitmap.Create;
[red] bmp.Width:=100;
bmp.Height:=100;[/red]
bmp.Canvas.CopyRect(Rect(0,0,100,100),c,Rect(0,0,100,100));
bmp.SaveToFile('C:/1.bmp');
bmp.Free;
end;

多人接受答案了。