iOS使用WebView生成长截图的第3种解决方案

extension UIScrollView {
 public func takeSnapshotOfFullContent() -> UIImage? {
  let originalFrame = self.frame
  let originalOffset = self.contentOffset

  self.frame = CGRect.init(origin: originalFrame.origin, size: self.contentSize)
  self.contentOffset = .zero

  let backgroundColor = self.backgroundColor ?? UIColor.white

  UIGraphicsBeginImageContextWithOptions(self.bounds.size, true, 0)

  guard let context = UIGraphicsGetCurrentContext() else {
   return nil
  }
  context.setFillColor(backgroundColor.cgColor)
  context.setStrokeColor(backgroundColor.cgColor)

  self.drawHierarchy(in: self.bounds, afterScreenUpdates: true)
  let image = UIGraphicsGetImageFromCurrentImageContext()
  UIGraphicsEndImageContext()

  self.frame = originalFrame
  self.contentOffset = originalOffset

  return image
 }
}

// example code
 private func takeSnapshotOfUIWebView() {
 let image = self.webView.scrollView.takeSnapshotOfFullContent()
 // 处理image
} 

extension UIScrollView {
 public func takeScreenshotOfFullContent(_ completion: @escaping ((UIImage?) -> Void)) {
  // 分页绘制内容到ImageContext
  let originalOffset = self.contentOffset

  // 当contentSize.height<bounds.height时，保证至少有1页的内容绘制
  var pageNum = 1
  if self.contentSize.height > self.bounds.height {
   pageNum = Int(floorf(Float(self.contentSize.height / self.bounds.height)))
  }

  let backgroundColor = self.backgroundColor ?? UIColor.white

  UIGraphicsBeginImageContextWithOptions(self.contentSize, true, 0)

  guard let context = UIGraphicsGetCurrentContext() else {
   completion(nil)
   return
  }
  context.setFillColor(backgroundColor.cgColor)
  context.setStrokeColor(backgroundColor.cgColor)

  self.drawScreenshotOfPageContent(0, maxIndex: pageNum) {
   let image = UIGraphicsGetImageFromCurrentImageContext()
   UIGraphicsEndImageContext()
   self.contentOffset = originalOffset
   completion(image)
  }
 }

 fileprivate func drawScreenshotOfPageContent(_ index: Int, maxIndex: Int, completion: @escaping () -> Void) {

  self.setContentOffset(CGPoint(x: 0, y: CGFloat(index) * self.frame.size.height), animated: false)
  let pageFrame = CGRect(x: 0, y: CGFloat(index) * self.frame.size.height, width: self.bounds.size.width, height: self.bounds.size.height)

  DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.3) {
   self.drawHierarchy(in: pageFrame, afterScreenUpdates: true)

   if index < maxIndex {
    self.drawScreenshotOfPageContent(index + 1, maxIndex: maxIndex, completion: completion)
   }else{
    completion()
   }
  }
 }
}

// example code
private func takeSnapshotOfUIWebView() {
 self.uiWebView.scrollView.takeScreenshotOfFullContent { (image) in
  // 处理image
 }
}

private func takeSnapshotOfWKWebView() {
 self.wkWebView.scrollView.takeScreenshotOfFullContent { (image) in
  // 处理image
 }
}

import UIKit
import WebKit

/// WebViewPrintPageRenderer: use to print the full content of webview into one image
internal final class WebViewPrintPageRenderer: UIPrintPageRenderer {

 private var formatter: UIPrintFormatter

 private var contentSize: CGSize

 /// 生成PrintPageRenderer实例
 ///
 /// - Parameters:
 /// - formatter: WebView的viewPrintFormatter
 /// - contentSize: WebView的ContentSize
 required init(formatter: UIPrintFormatter, contentSize: CGSize) {
  self.formatter = formatter
  self.contentSize = contentSize
  super.init()
  self.addPrintFormatter(formatter, startingAtPageAt: 0)
 }

 override var paperRect: CGRect {
  return CGRect.init(origin: .zero, size: contentSize)
 }

 override var printableRect: CGRect {
  return CGRect.init(origin: .zero, size: contentSize)
 }

 private func printContentToPDFPage() -> CGPDFPage? {
  let data = NSMutableData()
  UIGraphicsBeginPDFContextToData(data, self.paperRect, nil)
  self.prepare(forDrawingPages: NSMakeRange(0, 1))
  let bounds = UIGraphicsGetPDFContextBounds()
  UIGraphicsBeginPDFPage()
  self.drawPage(at: 0, in: bounds)
  UIGraphicsEndPDFContext()

  let cfData = data as CFData
  guard let provider = CGDataProvider.init(data: cfData) else {
   return nil
  }
  let pdfDocument = CGPDFDocument.init(provider)
  let pdfPage = pdfDocument?.page(at: 1)

  return pdfPage
 }

 private func covertPDFPageToImage(_ pdfPage: CGPDFPage) -> UIImage? {
  let pageRect = pdfPage.getBoxRect(.trimBox)
  let contentSize = CGSize.init(width: floor(pageRect.size.width), height: floor(pageRect.size.height))

  // usually you want UIGraphicsBeginImageContextWithOptions last parameter to be 0.0 as this will us the device's scale
  UIGraphicsBeginImageContextWithOptions(contentSize, true, 2.0)
  guard let context = UIGraphicsGetCurrentContext() else {
   return nil
  }

  context.setFillColor(UIColor.white.cgColor)
  context.setStrokeColor(UIColor.white.cgColor)
  context.fill(pageRect)

  context.saveGState()
  context.translateBy(x: 0, y: contentSize.height)
  context.scaleBy(x: 1.0, y: -1.0)

  context.interpolationQuality = .low
  context.setRenderingIntent(.defaultIntent)
  context.drawPDFPage(pdfPage)
  context.restoreGState()

  let image = UIGraphicsGetImageFromCurrentImageContext()
  UIGraphicsEndImageContext()

  return image
 }

 /// print the full content of webview into one image
 ///
 /// - Important: if the size of content is very large, then the size of image will be also very large
 /// - Returns: UIImage?
 internal func printContentToImage() -> UIImage? {
  guard let pdfPage = self.printContentToPDFPage() else {
   return nil
  }

  let image = self.covertPDFPageToImage(pdfPage)
  return image
 }
}

extension UIWebView {
 public func takeScreenshotOfFullContent(_ completion: @escaping ((UIImage?) -> Void)) {
  self.scrollView.setContentOffset(CGPoint(x: 0, y: 0), animated: false)
  DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.3) {
   let renderer = WebViewPrintPageRenderer.init(formatter: self.viewPrintFormatter(), contentSize: self.scrollView.contentSize)
   let image = renderer.printContentToImage()
   completion(image)
  }
 }
}

extension WKWebView {
 public func takeScreenshotOfFullContent(_ completion: @escaping ((UIImage?) -> Void)) {
  self.scrollView.setContentOffset(CGPoint(x: 0, y: 0), animated: false)
  DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.3) {
   let renderer = WebViewPrintPageRenderer.init(formatter: self.viewPrintFormatter(), contentSize: self.scrollView.contentSize)
   let image = renderer.printContentToImage()
   completion(image)
  }
 }
}

// example code
private func takeSnapshotOfUIWebView() {
 self.uiWebView.scrollView.takeScreenshotOfFullContent { (image) in
  // 处理image
 }
}

private func takeSnapshotOfWKWebView() {
 self.wkWebView.scrollView.takeScreenshotOfFullContent { (image) in
  // 处理image
 }
}