如何从PDF获取UIImage

Question

Url让我获得pdf。我需要一个4页的pdf文件来获取UIImage，但不是全部，而只是页面的一部分。请告诉我如何使这更容易。感谢您花费的时间

Answer 1

以下两个Swift 4.2 / iOS 12策略显示了如何从PDF文件页面获取UIImage。从PDF文件页面中提取特定帧作为练习。

＃1。使用PDFDocument和PDFPage＆＃39; draw(with:to:)方法（需要iOS 11）

PDFPage有一个名为draw(with:to:)的方法。 draw(with:to:)有以下声明：

func draw(with box: PDFDisplayBox, to context: CGContext)

以下Playground代码显示了如何使用UIImage PDFPage方法从PDF文件创建draw(with:to:)：

import UIKit
import PDFKit
import PlaygroundSupport

let url = Bundle.main.url(forResource: "Invoice", withExtension: "pdf")!
let document = PDFDocument(url: url)!
let page = document.page(at: 0)!
let rect = page.bounds(for: PDFDisplayBox.mediaBox).applying(page.transform(for: .mediaBox))
let renderer = UIGraphicsImageRenderer(size: rect.size)

let image = renderer.image(actions: { context in
    let cgContext = context.cgContext
    let rect = cgContext.boundingBoxOfClipPath

    cgContext.setFillColor(gray: 1, alpha: 1)
    cgContext.fill(rect)
    cgContext.translateBy(x: 0, y: rect.size.height)
    cgContext.scaleBy(x: 1, y: -1)

    page.draw(with: PDFDisplayBox.mediaBox, to: cgContext)
})

let imageView = UIImageView(image: image)
imageView.contentMode = .scaleAspectFit
PlaygroundPage.current.liveView = imageView

＃2。使用CGPDFDocument和CGContext＆＃39; drawPDFPage(_:)方法

CGContext有一个名为drawPDFPage(_:)的方法。 drawPDFPage(_:)有以下声明：

func drawPDFPage(_ page: CGPDFPage)

  

将PDF页面的内容绘制到当前图形上下文中。

以下操场代码显示如何使用UIImage CGContext方法从PDF文件创建drawPDFPage(_:)：

没有页面轮换管理的代码

import UIKit
import PlaygroundSupport

let url = Bundle.main.url(forResource: "Invoice", withExtension: "pdf")!
let document = CGPDFDocument(url as CFURL)!
let page = document.page(at: 1)!
let rect = page.getBoxRect(CGPDFBox.mediaBox)
let renderer = UIGraphicsImageRenderer(size: rect.size)

let image = renderer.image(actions: { context in
    let cgContext = context.cgContext

    cgContext.setFillColor(gray: 1, alpha: 1)
    cgContext.fill(rect)
    cgContext.translateBy(x: 0, y: rect.size.height)
    cgContext.scaleBy(x: 1, y: -1)

    cgContext.drawPDFPage(page)
})

let imageView = UIImageView(image: image)
imageView.contentMode = .scaleAspectFit
PlaygroundPage.current.liveView = imageView

管理页面轮换的替代代码。注意：由于使用CGPDFPage＆＃39; getDrawingTransform(_:rect:rotate:preserveAspectRatio:)，图片将按比例缩小

import UIKit
import PlaygroundSupport

let url = Bundle.main.url(forResource: "Invoice", withExtension: "pdf")!
let document = CGPDFDocument(url as CFURL)!
let page = document.page(at: 1)!
let rect = page.getBoxRect(CGPDFBox.mediaBox)
let drawSize = rect.applying(page.getDrawingTransform(.mediaBox, rect: rect, rotate: 0, preserveAspectRatio: true)).size
let renderer = UIGraphicsImageRenderer(size: drawSize)

let image = renderer.image(actions: { context in
    let cgContext = context.cgContext
    let rect = cgContext.boundingBoxOfClipPath

    cgContext.setFillColor(gray: 1, alpha: 1)
    cgContext.fill(rect)
    cgContext.scaleBy(x: 1, y: -1)
    cgContext.translateBy(x: 0, y: -rect.size.height)
    cgContext.concatenate(page.getDrawingTransform(.mediaBox, rect: rect, rotate: 0, preserveAspectRatio: true))

    cgContext.drawPDFPage(page)
})

let imageView = UIImageView(image: image)
imageView.contentMode = .scaleAspectFit
PlaygroundPage.current.liveView = imageView

Answer 2

使用此框架将UIImage转换为PDF。

https://github.com/mindbrix/UIImage-PDF