使用PDFKIT在PDF的所有页面上绘制文本

Question

我正在使用以下代码在PDF文档上绘制文本。这似乎仅在单个页面上绘制文本。 。如何在所有页面上绘制字符串？

var pdffile=PDFDocument(url: input)
let data = NSMutableData()
let consumer = CGDataConsumer(data: data as CFMutableData)!
for y in stride(from: 0, to: pdffile!.pageCount, by: 1)
{
    let page: PDFPage = pdffile!.page(at: y)!
    let outputBounds = page.bounds(for: PDFDisplayBox.mediaBox)
    var mediaBox = CGRect(x: 0, y: 0, width: outputBounds.size.width, height: outputBounds.size.height)
    let context = CGContext(consumer: consumer, mediaBox: &mediaBox, nil)!
    NSGraphicsContext.current = NSGraphicsContext(cgContext: context, flipped: false)

    context.beginPDFPage(nil)
    page.draw(with: .mediaBox, to: context)
    text.draw(in:drawrect,withAttributes:textFontAttributes);
    context.endPDFPage()
    context.closePDF()
}
let anotherDocument = PDFDocument(data:data as Data)
pdfview.document=anotherDocument

Answer 1

这里的主要问题是重新创建的上下文，对于我们应该写入相同上下文的多个页面（它通过beginpdfpage/endpdfpage对管理页面）。

这是固定的代码。用Xcode 13.4 / MacOS测试12.4

let pdffile = PDFDocument(url: input)
let data = NSMutableData()
let consumer = CGDataConsumer(data: data as CFMutableData)!

// create common context with no mediaBox, we will add it later
// per-page (because, actually they might be different)
let context = CGContext(consumer: consumer, mediaBox: nil, nil)!

for y in stride(from: 0, to: pdffile!.pageCount, by: 1)
{
    let page: PDFPage = pdffile!.page(at: y)!

    // re-use media box of original document as-is w/o changes !!
    var mediaBox = page.bounds(for: PDFDisplayBox.mediaBox)
    NSGraphicsContext.current = NSGraphicsContext(cgContext: context, flipped: false)

    // prepare mediaBox data for page setup
    let rectData = NSData(bytes: &mediaBox, length: MemoryLayout.size(ofValue: mediaBox))

    context.beginPDFPage([kCGPDFContextMediaBox as String: rectData] as CFDictionary)   // << here !!

    page.draw(with: .mediaBox, to: context) // << original !!
    text.draw(in:drawrect,withAttributes:textFontAttributes) // << over !!

    context.endPDFPage()
}
context.closePDF()  // close entire document

let anotherDocument = PDFDocument(data:data as Data)
// ... as used before