Photoshop script to save the current selection to a PNG

app.displayDialogs = DialogModes.NO;

var pngSaveOptions = new PNGSaveOptions();
pngSaveOptions.compression = 9;

var hasSelection;
var docRef;
try {
    hasSelection = !!app.activeDocument.selection.bounds;
} catch (err) {
    hasSelection = false;
}

if (hasSelection) {
    app.activeDocument.selection.copy(true);
    var w = app.activeDocument.selection.bounds[2];
    var h = app.activeDocument.selection.bounds[3];
    docRef = app.documents.add(w, h, null, null, null, DocumentFill.TRANSPARENT);
    docRef.paste();
} else {
    docRef = app.activeDocument;
}

docRef.trim(TrimType.TRANSPARENT);

var file = File.saveDialog("Export as PNG to...");
if (file && ((file.exists && confirm("Overwrite " + file +"?")) || !file.exists)) {
    docRef.saveAs(file, pngSaveOptions, !hasSelection, Extension.LOWERCASE);
    if (hasSelection) {
    docRef.close(SaveOptions.DONOTSAVECHANGES);
    }
}