TileCutterNamer.js and Custom Maps

Hello all.

I have been playing around with the tile cutting script for Photoshop
which is mentioned in the tutorial for making custom maps over at MapKi
(http://mapki.com/index.php?title=Automatic_Tile_Cutter)

I am new to using javascript to manipulate Photoshop, so my question is
this: what modification is needed in order to save transparent PNG
files?

I know there is this code at the bottom:

//Set path to file and file name
saveFile = new File(FolderPath + TileX+ "_" + TileY+ "_" +
ZoomLevel + ".gif");
//Set save options
gifSaveOptions = new GIFSaveOptions();
gifSaveOptions.colors = 64;
gifSaveOptions.dither = Dither.NONE;
gifSaveOptions.matte = MatteType.NONE;
gifSaveOptions.preserveExactColors = 0;
gifSaveOptions.transparency = 0;
gifSaveOptions.interlaced = 0;

//Save the file and close it
saveMe.saveAs(saveFile, gifSaveOptions, true,Extension.LOWERCASE);
saveMe.close(SaveOptions.DONOTSAVECHANGES);

But I am not familiar with the settings necessary PNG's. Outside of
the save options changes, it looks like I would just need to change the
file extension to '.png'.

Reason for request, I am trying to create some line overlays to put
over a map, but I have tweaked the GIF options and tried saving as
transparent gif's to no avail...I still get my lines on a white
background. I am hoping that transparent PNG's will do the trick.

Has anyone accomplished this yet?

thanks,

Brian