I try to rotate a page 180° in a pdf file.
I nearly get it, but the page is also mirrored horizontally. Some images to illustrate:
Initial page:
Result after rotation (see code): it is rotated 180° BUT mirrored horizontally as well:
The expected result
It is just as if it was rotated 180°, around the x axis of the page. And I would need to rotate 180° around z axis (perpendicular to the page). It is probably the result of
writeContext!.scaleBy(x: 1, y: -1)
I have tried a lot of changes for transform, translate, scale parameters, including removing calls to some of them, to no avail.
@IBAction func createNewPDF(_ sender: UIButton) {
var originalPdfDocument: CGPDFDocument!
let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let documentsDirectory = urls[0]
// read some pdf from bundle for test
if let path = Bundle.main.path(forResource: "Test", ofType: "pdf"), let pdf = CGPDFDocument(URL(fileURLWithPath: path) as CFURL) {
originalPdfDocument = pdf
} else { return }
// create new pdf
let modifiedPdfURL = documentsDirectory.appendingPathComponent("Modified.pdf")
guard let page = originalPdfDocument.page(at: 1) else { return } // Starts at page 1
var mediaBox: CGRect = page.getBoxRect(CGPDFBox.mediaBox) // mediabox which will set the height and width of page
let writeContext = CGContext(modifiedPdfURL as CFURL, mediaBox: &mediaBox, nil) // get the context
var pageRect: CGRect = page.getBoxRect(CGPDFBox.mediaBox) // get the page rect
writeContext!.beginPage(mediaBox: &pageRect)
let m = page.getDrawingTransform(.mediaBox, rect: mediaBox, rotate: 0, preserveAspectRatio: true) // Because of rotate 0, no effect ; changed rotate to 180, then get an empty page
writeContext!.translateBy(x: 0, y: pageRect.size.height)
writeContext!.scaleBy(x: 1, y: -1)
writeContext!.concatenate(m)
writeContext!.clip(to: pageRect)
writeContext!.drawPDFPage(page) // draw content in page
writeContext!.endPage() // end the current page
writeContext!.closePDF()
}
Note: This is a follow up of a previous thread, https://developer.apple.com/forums/thread/688436
Finally fixed it:
I added a "rotation" along y axis, and now get the correct result:
// -->> REMOVED THIS. let m = page.getDrawingTransform(.mediaBox, rect: mediaBox, rotate: 0, preserveAspectRatio: true)
writeContext!.translateBy(x: 0, y: pageRect.size.height)
writeContext!.scaleBy(x: 1, y: -1)
writeContext!.translateBy(x: pageRect.size.width, y: 0) // <<<--- ADDED These 2 lines
writeContext!.scaleBy(x: -1, y: 1)
// -->> REMOVED THIS. writeContext!.concatenate(m)
or equivalent :
writeContext!.translateBy(x: pageRect.size.width y: pageRect.size.height)
writeContext!.scaleBy(x: -1, y: -1)
