When saving an NSView content into a pdf file, transparency is lost

I have an NSView in which i do some custom drawing using NSBezierPaths. Some of the paths are drawn transparent using:

NSGraphicsContext.saveGraphicsState()
NSGraphicsContext.current!.compositingOperation = NSCompositingOperation.clear
            // Do the path drawing here

NSGraphicsContext.restoreGraphicsState()


The NSView draws all paths as expected. But when, later, i get the view content, transform it to NSData and save it to a file using code like this..

let pdfData = self.dataWithPDF(inside: bounds)
let pdfNSData = NSData.init(data: pdfData)
pdfNSData.write(toFile: "/Users/aUser/Downloads/image.pdf", atomically: true)


the PDF file is created but in the place of the transparent NSBezierPaths i get paths filled with black color. Is this a Cocoa API problem?

Or am i missing something?


I am using Xcode 9.3 and Apple Swift version 4.1

Thanks in advance!!!