delphi高手进来看看啊,有关图像缩放的问题!!!!

function TMainForm.JResize(src1, dst: String): Boolean;
var
    Bmp: TBitmap;
    Jpeg: TJpegImage;
begin     if (ExtractFileExt(src1)='.JPG') or (ExtractFileExt(src1)='.jpg')  then
     begin
           Jpeg := TJpegImage.Create;
        try
           Jpeg.LoadFromFile(src1);
           Bmp := TBitmap.Create;
           try
              Bmp.Width := StrToInt(edtNewWidth.Text);
              Bmp.Height := StrToInt(edtNewHeight.Text);
              Bmp.Canvas.StretchDraw(Rect(0, 0, Bmp.Width, Bmp.Height), Jpeg);
              Jpeg.Assign(Bmp);
            finally
              Bmp.Free;
           end;
              Jpeg.SaveToFile(dst);
        finally
              Jpeg.Free;
              Screen.Cursor := crDefault;
        end;
     end;     if (ExtractFileExt(src1)='.BMP') or (ExtractFileExt(src1)='.bmp') then
     begin
           Bmp := TBitmap.Create;
        try
           Bmp.LoadFromFile(src1);
           
           try
              Bmp.Width := StrToInt(edtNewWidth.Text);
              Bmp.Height := StrToInt(edtNewHeight.Text);
              Bmp.Canvas.StretchDraw(Rect(0, 0, Bmp.Width, Bmp.Height), Bmp);
              Bmp.Assign(Bmp);
           finally
              Bmp.Free;
           end;
           Bmp.SaveToFile(dst);
        finally
             Screen.Cursor := crDefault;
        end;
     end;
     result := true;
end;缩放jpeg和bmp,jpeg可以实现,但是bmp却报错,哪位大侠给看看,指点一下~~~~