general code snippets

convertPDFToImage.swift

//swift 4.0    

func convertpdfToImage(url: URL) -> UIImage? {
        guard let document = CGPDFDocument(url as CFURL) else { return nil }
        guard let page = document.page(at: 1) else { return nil }
        let pageRect = page.getBoxRect(.mediaBox)
        let renderer = UIGraphicsImageRenderer(size: pageRect.size)
        let img = renderer.image { ctx in
            UIColor.white.set()
            ctx.fill(pageRect)
            
            ctx.cgContext.translateBy(x: 0.0, y: pageRect.size.height)
            ctx.cgContext.scaleBy(x: 1.0, y: -1.0)
            
            ctx.cgContext.drawPDFPage(page)
        }
        return img
    }

convertStringToPdf.swift

//swift 4.0    

func convertStringOfHtmlToPdf(htmlString : String, filename: String) -> String{
        // 1. Create a print formatter
        var returnString = ""
        let html = htmlString
        let fmt = UIMarkupTextPrintFormatter(markupText: html)
        
        // 2. Assign print formatter to UIPrintPageRenderer
        let render = UIPrintPageRenderer()
        render.addPrintFormatter(fmt, startingAtPageAt: 0)
        
        // 3. Assign paperRect and printableRect
        let page = CGRect(x: 0, y: 0, width: 595.2, height: 841.8) // A4, 72 dpi
        render.setValue(page, forKey: "paperRect")
        render.setValue(page, forKey: "printableRect")
        
        // 4. Create PDF context and draw
        let pdfData = NSMutableData()
        UIGraphicsBeginPDFContextToData(pdfData, .zero, nil)
        
        for i in 0..<render.numberOfPages {
            UIGraphicsBeginPDFPage();
            render.drawPage(at: i, in: UIGraphicsGetPDFContextBounds())
        }
        UIGraphicsEndPDFContext();
        
        // 5. Save PDF file
        guard let outputURL = try? FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false).appendingPathComponent(filename).appendingPathExtension("pdf")
            else { fatalError("Destination URL not created") }
        
        pdfData.write(to: outputURL, atomically: true)
        print("open \(outputURL.path)") // command to open the generated file
        returnString = "\(outputURL.path)"
        //        self.globalVar.set(outputURL.path, forKey: "file_path")
        return returnString
    }

createPDFDocument.swift

    func convertPDFToData(pages: [PDFPage]) -> Data {
        //this portion below convert back the resulting image to pdf
        let pdfDocument = PDFDocument()

        //iterate the list of pdf pages and insert into the PDFDocument object
        for (index, element) in pages.enumerated() {
            // Insert the PDF page into your document
            pdfDocument.insert(element, at: index )
        }
        // Get the raw data of your PDF document
        let data = pdfDocument.dataRepresentation()

        return data!
    }

displayPDFDataToWebKit.swift

let data = self.convertImageBackToPdf(pages: master_pdf)
        // load the data intot the wkwebkit
        self.webPreview.load(data, mimeType: "application/pdf", characterEncodingName: "", baseURL: url)
        // The url to save the data to
        let file_path = self.saveDataToLocalFile(data: data)
        globalVar.set(file_path, forKey: "file_path")

mergeSignature.swift

let atPoint = CGPoint(x: 400, y: 300) // to specify where we want to place the signature
let newImage = self.mergingSignatureOnPdfImage(signatureImage: signature!, pdfImage: convertpdftoimage!, atPoint: atPoint)

    func mergingSignatureOnPdfImage(signatureImage : UIImage, pdfImage: UIImage, atPoint: CGPoint) -> UIImage{
        
        UIGraphicsBeginImageContextWithOptions((pdfImage.size), false, 0.0)
        //first, draw the pdf image
        pdfImage.draw(in: CGRect(x: 0, y: 0, width: (pdfImage.size.width) , height: (pdfImage.size.height)))
        
        //width and height here are adjustable according to your preference
        let rect2: CGRect = CGRect(x: atPoint.x, y: atPoint.y + 140, width: 200  , height: 100 )
        //Now Draw the signature into an image.
        signatureImage.draw(in: rect2)
        
        //try add the QR image here
        let QR_image = Service.sharedInstance.generateQRCode(from: "https://www.apple.com") as! UIImage
        
        let rect3: CGRect = CGRect(x: atPoint.x + 50, y: atPoint.y - 265 , width: 100  , height: 100 )
//        QR_image.draw(in: rect3)
        
        // now we get the resulting image which are signature on top of the pdf
        let newImage = UIGraphicsGetImageFromCurrentImageContext()!
        
        // End the context now that we have the image we need
        UIGraphicsEndImageContext()
        return newImage
    }