The Google Script will fetch an image file, convert it to PDF and sends it as an image attachment using the Gmail service. The image file can be on your Google Drive or it can be on web (specify the image URL as the filename).

Also see: How to Convert Files

function convertImageToPDF(filename) {
  var image;

  // Is it a local file or web URL?
  if (filename.match(/^https?:\/\//i)) {
    image = UrlFetchApp.fetch(filename);
  } else {
    image = DriveApp.getFilesByName(filename).next();
  }

  // grab its bytes and base64-encode them.
  var base64 = Utilities.base64Encode(image.getBlob().getBytes());
  var html = '<img src="data:image/png;base64,' + base64 + '" />';

  // create a blob, convert to PDF
  var blob = Utilities.newBlob(html, MimeType.HTML).setName(filename + '.pdf');

  MailApp.sendEmail('ctrlq@labnol.org', 'Image to PDF', '', {
    attachments: blob.getAs(MimeType.PDF),
  });
}