Drawing oval on gif image

Hi I am trying to draw an oval on all gif images inside a folder. Here is my macro for that

dir1 = getDirectory("");
dir2 = getDirectory(" ");
list = getFileList(dir1);
setBatchMode(true);
for (i=0; i<list.length; i++) {
showProgress(i+1, list.length);
filename = dir1 + list[i];
if (endsWith(filename, “gif”)) {
open(filename);
x = 50;
y = 30;

    drawOval(x, y, 40, 50);

	saveAs("gif", dir2+list[i]);      
	close() ;
}

}

The macro did draw an oval on all gif images inside the selected folder. But the drawing (oval) is only on the first slice, not on all slices. I want oval on all slices of each gif.
How can I do that?

Thank you
Win