Converting PDF to Image - Swift iOS - ios

Question

I am trying to convert a PDF file and all its pages to png images.
I have put together the code below filling the example on this thread
How to convert PDF to PNG efficiently?
When I run the code, it crashes on the pdf file source (sourceURL) there is definitely a file there. and when I print sourceURl it prints the URL to the file.
The crash says it found nil - My understanding is that means it could not find the file? even though I can physically see and open the file and also print the URL to the file.
Can someone point out what I'm doing wrong?
Code:
func convertPDFtoPNG() {
let sourceURL = pptURL
print("pptURL:", pptURL!)
let destinationURL = pngURL
let urls = try? convertPDF(at: sourceURL!, to: destinationURL!, fileType: .png, dpi: 200)
}
func convertPDF(at sourceURL: URL, to destinationURL: URL, fileType: ImageFileType, dpi: CGFloat = 200) throws -> [URL] {
let pdfDocument: CGPDFDocument! = CGPDFDocument(sourceURL as CFURL)! //Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGImageAlphaInfo.noneSkipLast.rawValue
var urls = [URL](repeating: URL(fileURLWithPath : "/"), count: pdfDocument.numberOfPages)
DispatchQueue.concurrentPerform(iterations: pdfDocument.numberOfPages) { i in
let pdfPage = pdfDocument.page(at: i + 1)!
let mediaBoxRect = pdfPage.getBoxRect(.mediaBox)
let scale = dpi / 72.0
let width = Int(mediaBoxRect.width * scale)
let height = Int(mediaBoxRect.height * scale)
let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: bitmapInfo)!
context.interpolationQuality = .high
context.fill(CGRect(x: 0, y: 0, width: width, height: height))
context.scaleBy(x: scale, y: scale)
context.drawPDFPage(pdfPage)
let image = context.makeImage()!
let imageName = sourceURL.deletingPathExtension().lastPathComponent
let imageURL = destinationURL.appendingPathComponent("\(imageName)-Page\(i+1).\(fileType.fileExtention)")
let imageDestination = CGImageDestinationCreateWithURL(imageURL as CFURL, fileType.uti, 1, nil)!
CGImageDestinationAddImage(imageDestination, image, nil)
CGImageDestinationFinalize(imageDestination)
urls[i] = imageURL
}
return urls
}

Answer 1

import Foundation
import Photos
// 1: 目前主要用来操作pdf转为图片
// 2: 图片保存到自定义相册中
struct HBPhotosAlbumHelperUtil {
static let shared = HBPhotosAlbumHelperUtil()
// url链接的pdf转为image
// pageNumber :表示pdf的对应的页面，默认为第一页
func drawToImagePDFFromURL(pdfurl url: String?, pageNumber index: Int = 1, scaleX scalex: CGFloat = 1.0, scaleY scaley: CGFloat = -1.0) -> UIImage? {
guard let pdfUrl = url, pdfUrl.count > 0, let formatterUrl = pdfUrl.urlValue else {
return nil
}
guard let document = CGPDFDocument(formatterUrl as CFURL) else {
return nil
}
guard let page = document.page(at: index) else {
return nil
}
let pageRect = page.getBoxRect(.mediaBox)
if #available(iOS 10.0, *) {
let renderGraph = UIGraphicsImageRenderer(size: pageRect.size)
let drawImage = renderGraph.image { context in
UIColor.white.set()
context.fill(pageRect)
context.cgContext.translateBy(x: 0.0, y: pageRect.size.height)
context.cgContext.scaleBy(x: scalex, y: scaley)
context.cgContext.drawPDFPage(page)
}
return drawImage
} else {
UIGraphicsBeginImageContextWithOptions(pageRect.size, false, 1.0)
let context = UIGraphicsGetCurrentContext()
context?.setFillColor(UIColor.white.cgColor)
context?.fill(pageRect)
context?.translateBy(x: 0.0, y: pageRect.size.height)
context?.scaleBy(x: scalex, y: scaley)
context?.drawPDFPage(page)
let pdfImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return pdfImage
}
}
}
// 用来表示保存图片到自定义相册或者系统相册的操作结果
enum HBPhotosAlbumUtilResult {
case success, error, denied
}
extension HBPhotosAlbumHelperUtil {
// 请求获取操作系统相册权限
// 返回true说明已经得到授权
static var photoAlbumAuthorized: Bool {
return PHPhotoLibrary.authorizationStatus() == .authorized || PHPhotoLibrary.authorizationStatus() == .notDetermined
}
// 保存图片到自定义相册中
func saveImageToCustomAlbum(saveImage markImage: UIImage, customAlbumName albumName: String = "丰巢管家电子发票", completion: ((_ result: HBPhotosAlbumUtilResult) -> Void)?) {
guard HBPhotosAlbumHelperUtil.photoAlbumAuthorized else {
completion?(.denied)
return
}
var assetAlbum: PHAssetCollection?
// 如果相册名称为空，则图片默认保存到系统相册里面
if albumName.isEmpty {
let assetCollection = PHAssetCollection.fetchAssetCollections(with: .smartAlbum, subtype: .smartAlbumUserLibrary,
options: nil)
assetAlbum = assetCollection.firstObject
} else {
// 获取指定的相册是否存在
let assetList = PHAssetCollection.fetchAssetCollections(with: .album, subtype: .any, options: nil)
assetList.enumerateObjects { albumOption, _, stop in
let assetCollection = albumOption
if albumName == assetCollection.localizedTitle {
assetAlbum = assetCollection
stop.initialize(to: true)
}
}
// 自定义相册不存在就创建
if assetAlbum == nil {
PHPhotoLibrary.shared().performChanges({
PHAssetCollectionChangeRequest.creationRequestForAssetCollection(withTitle: albumName)
}) { _, _ in
self.saveImageToCustomAlbum(saveImage: markImage, customAlbumName: albumName, completion: completion)
}
}
}
// 保存图片
PHPhotoLibrary.shared().performChanges({
let result = PHAssetChangeRequest.creationRequestForAsset(from: markImage)
if !albumName.isEmpty {
if let assetPlaceHolder = result.placeholderForCreatedAsset,
let lastAssetAlbum = assetAlbum,
let albumChangeRequset = PHAssetCollectionChangeRequest(for:
lastAssetAlbum) {
albumChangeRequset.addAssets([assetPlaceHolder] as NSArray)
}
}
}) { isSuccess, _ in
guard isSuccess else {
completion?(.error)
return
}
completion?(.success)
}
}
}
extension String {
/// URL legalization
public var urlValue: URL? {
if let url = URL(string: self) {
return url
}
var set = CharacterSet()
set.formUnion(.urlHostAllowed)
set.formUnion(.urlPathAllowed)
set.formUnion(.urlQueryAllowed)
set.formUnion(.urlFragmentAllowed)
return self.addingPercentEncoding(withAllowedCharacters: set).flatMap { URL(string: $0) }
}
}
You can use the api like this:
// Use this way to achieve pdf to image
HBPhotosAlbumHelperUtil.shared.drawToImagePDFFromURL(pdfurl: "link to pdf file")
// In this way, you can save pictures to the system custom album.
HBPhotosAlbumHelperUtil.shared.saveImageToCustomAlbum(saveImage: UIImage()) { (result) in
}

Answer 2

Make sure that your pptURL is file url.
URL(string: "path/to/pdf") and URL(fileURLWithPath: "path/to/pdf") are different things and you must use the last one while initiating your url.
The output should start with "file:///" prefix, f.e.
file:///Users/dev/Library/Developer/CoreSimulator/Devices/4FF18699-D82F-4308-88D6-44E3C11C955A/data/Containers/Bundle/Application/8F230041-AC15-45D9-863F-5778B565B12F/myApp.app/example.pdf