Downloading a Google Slides presentation as PowerPoint doc using Google Apps Script? - google-apps-script

Question

The GUI of Google Slides offers to download a GSlides presentation as a Powerpoint (myFile.pptx). I could not find the equivalent in the Google Apps Script documentation - any pointer?
EDIT
Thanks to comments and answers, I tried this snippet:
function testFileOps() {
// Converts the file named 'Synthese' (which happens to be a Google Slide doc) into a pptx
var files = DriveApp.getFilesByName('Synthese');
var rootFolder = DriveApp.getRootFolder();
while (files.hasNext()) {
var file = files.next();
var blobPptx = file.getBlob().getAs('application/vnd.openxmlformats-officedocument.presentationml.presentation');
var result = rootFolder.createFile(blobPptx);
}
}
It returns an error:
Converting from application/vnd.google-apps.presentation to
application/vnd.openxmlformats-officedocument.presentationml.presentation
is not supported. (line 7, file "Code")
SECOND EDIT
As per another suggestion in comments, I tried to make an http call from Google App Script, that would directly convert the gslides into pptx, without size limit. It produces a file on G Drive, but this file is corrupted / unreadable. The GAS script:
function convertFileToPptx() {
// Converts a public Google Slide file into a pptx
var rootFolder = DriveApp.getRootFolder();
var response = UrlFetchApp.fetch('https://docs.google.com/presentation/d/1Zc4-yFoUYONXSLleV_IaFRlNk6flRKUuAw8M36VZe-4/export/pptx');
var blobPptx = response.getContent();
var result = rootFolder.createFile('test2.pptx',blobPptx,MimeType.MICROSOFT_POWERPOINT);
}
Notes:
I got the mime type for pptx here
using the mime type 'pptx' returns the same error message

Answer 1

How about this modification?
Modification point:
response.getContent() returns byte array. So please use response.getBlob().
Modified script:
function convertFileToPptx() {
var fileId = "1Zc4-yFoUYONXSLleV_IaFRlNk6flRKUuAw8M36VZe-4";
var outputFileName = "test2.pptx";
var url = 'https://docs.google.com/presentation/d/' + fileId + '/export/pptx';
var rootFolder = DriveApp.getRootFolder();
var response = UrlFetchApp.fetch(url);
var blobPptx = response.getBlob();
var result = rootFolder.createFile(blobPptx.setName(outputFileName));
}
Note:
If you want to convert Google Slides, which are not published, in your Google Drive, please use access token. At that time please modify url as follows.
var url = 'https://docs.google.com/presentation/d/' + fileId + '/export/pptx?access_token=' + ScriptApp.getOAuthToken();
DriveApp.createFile() creates a file on root folder as the default.
References:
Class HTTPResponse
getOAuthToken()

Answer 2

As mentioned by tehhowch, you could get the Google Slide file from your Drive and get it as a .pptx. (Not sure of mime type.)
File#getAs:

Answer 3

I add all modifications with token part and specific folder
function convertFileToPptx() {
var fileId = "Your File ID";
var outputFileName = "name.pptx";
var url = 'https://docs.google.com/presentation/d/' + fileId + '/export/pptx';
//var rootFolder = DriveApp.getRootFolder();
var rootFolder = DriveApp.getFolderById("Your Folder ID")
var params = {method:"GET", headers:{"authorization":"Bearer "+ ScriptApp.getOAuthToken()}};
var response = UrlFetchApp.fetch(url,params);
var blobPptx = response.getBlob();
var result = rootFolder.createFile(blobPptx.setName(outputFileName));
}

Answer 4

To get the byte[] do:
function downloadAsPPTX(){
var presentation = SlidesApp.getActivePresentation();
var fileId = presentation.getId();
var url = 'https://docs.google.com/presentation/d/' + fileId + '/export/pptx';
var response = UrlFetchApp.fetch(url);
var blobPptx = response.getBlob();
Logger.log("size: "+blobPptx.getBytes().length);
}