PDF Thumbnail Generator Always Returning Nil | Swift/Xcode - swift

Question

Would someone please explain to me why this pdf generator I'm attempting to use is always returning nil? I'm attempting to get a thumbnail to display in a UITableView alongside the filename of the PDF. Unfortunately, out of the four or so thumbnail generators I've tried, none of them have returned anything other than nil.
func uploadPDF() {
let types = UTType.types(tag: "pdf",
tagClass: UTTagClass.filenameExtension,
conformingTo: nil)
let documentPickerController = UIDocumentPickerViewController(forOpeningContentTypes: types)
documentPickerController.delegate = self
self.present(documentPickerController, animated: true, completion: nil)
}
func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
for url in urls {
let thumbnail = thumbnailFromPdf(withUrl: url, pageNumber: 0)
self.modelController.bidPDFUploadThumbnails.append(thumbnail!)
}
tableView.reloadData()
}
func thumbnailFromPdf(withUrl url:URL, pageNumber:Int, width: CGFloat = 240) -> UIImage? {
guard let pdf = CGPDFDocument(url as CFURL),
let page = pdf.page(at: pageNumber)
else {
return nil
}
var pageRect = page.getBoxRect(.mediaBox)
let pdfScale = width / pageRect.size.width
pageRect.size = CGSize(width: pageRect.size.width*pdfScale, height: pageRect.size.height*pdfScale)
pageRect.origin = .zero
UIGraphicsBeginImageContext(pageRect.size)
let context = UIGraphicsGetCurrentContext()!
// White BG
context.setFillColor(UIColor.white.cgColor)
context.fill(pageRect)
context.saveGState()
// Next 3 lines makes the rotations so that the page look in the right direction
context.translateBy(x: 0.0, y: pageRect.size.height)
context.scaleBy(x: 1.0, y: -1.0)
context.concatenate(page.getDrawingTransform(.mediaBox, rect: pageRect, rotate: 0, preserveAspectRatio: true))
context.drawPDFPage(page)
context.restoreGState()
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image
}
Generator source: Thumbnail Generator

Answer 1

the pdf document starts from page 1 not 0 because its not an array.
so simple is
let thumbnail = thumbnailFromPdf(withUrl: url, pageNumber: 1)
you'll get it
rather than using page number you can direct access the thumbnail of by default first page as follow:
import PDFKit
func generatePdfThumbnail(of thumbnailSize: CGSize , for documentUrl: URL, atPage pageIndex: Int) -> UIImage? {
let pdfDocument = PDFDocument(url: documentUrl)
let pdfDocumentPage = pdfDocument?.page(at: pageIndex)
return pdfDocumentPage?.thumbnail(of: thumbnailSize, for: PDFDisplayBox.trimBox)
}