Dialog.create("Listing eyelid ROI...");
Dialog.addChoice("which eyelid?", newArray("Top", "Bottom"));
Dialog.show();

channel = Dialog.getChoice();
savename = replace(getTitle(), ".png", "-"+channel+".txt");
savepath = getDirectory("image") + "/" + savename;
fp = File.open(savepath);
print(fp, "X,Y");
Roi.getContainedPoints(xp, yp);
for (i=0; i<xp.length; i++) {
    print(fp, toString(xp[i]) + "," + toString(yp[i]));
}
showMessage("saved as: "+savename);