在macOS上使用Swift绘制PDF [英] Draw on a PDF using Swift on macOS

问题描述

我的目标是在PDF上写文本，例如注释.

My goal is to write text on a PDF, like an annotation.

我实现了将PDFPage转换为NSImage的过程，我在NSImage上绘制了图像，然后保存了由图像形成的PDF.

I achieved it transforming the PDFPage to a NSImage, I drew on the NSImage then I saved the PDF formed by the images.

let image = NSImage(size: pageImage.size)        
image.lockFocus()

let rect: NSRect = NSRect(x: 50, y: 50, width: 60, height: 20)
"Write it on the page!".draw(in: rect, withAttributes: someAttributes)

image.unlockFocus()

let out = PDFPage(image: image)

问题显然是out(输出PDF的新页面)是图像的PDFPage，而不是常规页面.因此，输出的PDF很大，您不能在其上复制和粘贴任何内容.这只是一系列图像.

The problem is obviously that out (the new page of the output PDF) is a PDFPage of images and not a regular one. So the output PDF is very big in size and you can't copy and paste anything on it. It's just a sequence of images.

我的问题是，是否有一种方法可以在不使用NSImage的情况下以编程方式在PDF页面上添加简单文本.有什么主意吗?

My question is if there's a way to add simple text on a PDF page programmatically without using NSImage. Any idea?

注意::iOS编程UIGraphicsBeginPDFPageWithInfo中有一个此类，对我来说可能非常有帮助.但是我找不到用于macOS开发的类似类.

Note: There's this class in iOS programming UIGraphicsBeginPDFPageWithInfo which could be very helpful in my case. But I can't find the similar class for macOS development.

推荐答案

您可以在macOS上创建PDF图形上下文，并在其中绘制PDFPage.然后，您可以使用Core Graphics或AppKit图形将更多对象绘制到上下文中.

You can create a PDF graphics context on macOS and draw a PDFPage into it. Then you can draw more objects into the context using either Core Graphics or AppKit graphics.

这是我通过打印您的问题创建的测试PDF:

Here's a test PDF I created by printing your question:

这是将页面绘制到PDF上下文中，然后在页面顶部绘制更多文本的结果:

And here's the result from drawing that page into a PDF context, then drawing more text on top of it:

这是我编写的将第一个PDF转换为第二个PDF的代码:

Here's the code I wrote to transform the first PDF into the second PDF:

import Cocoa
import Quartz

let inUrl: URL = URL(fileURLWithPath: "/Users/mayoff/Desktop/test.pdf")
let outUrl: CFURL = URL(fileURLWithPath: "/Users/mayoff/Desktop/testout.pdf") as CFURL

let doc: PDFDocument = PDFDocument(url: inUrl)!
let page: PDFPage = doc.page(at: 0)!
var mediaBox: CGRect = page.bounds(for: .mediaBox)

let gc = CGContext(outUrl, mediaBox: &mediaBox, nil)!
let nsgc = NSGraphicsContext(cgContext: gc, flipped: false)
NSGraphicsContext.current = nsgc
gc.beginPDFPage(nil); do {
    page.draw(with: .mediaBox, to: gc)

    let style = NSMutableParagraphStyle()
    style.alignment = .center

    let richText = NSAttributedString(string: "Hello, world!", attributes: [
        NSFontAttributeName: NSFont.systemFont(ofSize: 64),
        NSForegroundColorAttributeName: NSColor.red,
        NSParagraphStyleAttributeName: style
        ])

    let richTextBounds = richText.size()
    let point = CGPoint(x: mediaBox.midX - richTextBounds.width / 2, y: mediaBox.midY - richTextBounds.height / 2)
    gc.saveGState(); do {
        gc.translateBy(x: point.x, y: point.y)
        gc.rotate(by: .pi / 5)
        richText.draw(at: .zero)
    }; gc.restoreGState()

}; gc.endPDFPage()
NSGraphicsContext.current = nil
gc.closePDF()

这篇关于在macOS上使用Swift绘制PDF的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！