Swift:如何像 iOS 13 的 Book 应用程序一样为 PDF 实现标记(注释)？

Question

我到处搜索，但找不到答案。我能找到的最接近的是

func saveAnnotations_forever() {
        //let documentAttributes = pdfDocument?.documentAttributes
        //let attachmentData = pdfDocument?.dataRepresentation()
        let currentPage = pdfView.currentPage
        let page_index = pdfDocument?.index(for: currentPage!)
        let documentURL = self.pdfDocument?.documentURL// URL to your PDF document.

        // Create a `PDFDocument` object using the URL.
        let pdfDocument = PDFDocument(url: documentURL!)!

        // `page` is of type `PDFPage`.
        let page = self.pdfDocument!.page(at: page_index!)!

         // Extract the crop box of the PDF. We need this to create an appropriate graphics context.
        let bounds = page.bounds(for: .mediaBox)


        // Create a `UIGraphicsImageRenderer` to use for drawing an image.
        let renderer = UIGraphicsImageRenderer(bounds: bounds, format: UIGraphicsImageRendererFormat.default())

        // This method returns an image and takes a block in which you can perform any kind of drawing.
        let image = renderer.image { (context) in
            // We transform the CTM to match the PDF's coordinate system, but only long enough to draw the page.
            context.cgContext.saveGState()

            context.cgContext.translateBy(x: 0, y: bounds.height)
            context.cgContext.concatenate(CGAffineTransform.init(scaleX: 1, y: -1))
            page.draw(with: .mediaBox, to: context.cgContext)

            context.cgContext.restoreGState()

以此类推，将注释和 PDF 页面一起呈现为图像。但是，我无法搜索带注释页面的文本(因为它是作为图像呈现的)，并且一旦保存，我就无法删除以前的注释。 iOS 的 Book 注释效果很好-我想实现这一点，但是如何实现？

提前致谢。

Answer 1

如果您尝试将注释保存为 PDF，不妨试试以下代码:

// add annotation to the current page
let rect = NSRect(x: 30, y: 30, width: 30, height: 30)
let annotation = PDFAnnotation(bounds: rect, forType: .text, withProperties: nil)
pdfView.currentPage?.addAnnotation(annotation)

// save the PDF to file
if let doc = self.document,
   let url = self.document?.documentURL {
    doc.write(to: url)
}

您可以使用 PDFAnnotation documentation进一步自定义注释。