PDF Parsing with Swift

How can I get all text from a PDF in Swift?

That is unfortunately not possible.

At least not without some major work on your part. And it certainly is not possible in a general matter for all pdfs.

PDFs are (generally) a one-way street.

They were created to display text in the same way on every system without any difference and for printers to print a document without the printer having to know all fonts and stuff.

Extracting text is non-trivial and only possible for some PDFs where the basic image-pdf is accompanied by text (which it does not have to). All text information present in the PDF is coupled with location information to determine where it is to be shown.

If you have a table shown in the PDF where the left column contains the names of the entries and the right row contains its contents, both of those columns can be represented as completely different blocks of text which only appear to have some link between each other due to the their placement next to each other.

What the framework / your code would have to do is determine what parts of text that are visually linked are also logically linked and belong together. That is not (yet) possible. The reason you and I can read and understand and group the PDF is that in some fields our brain is still far better than computers.

Final note because it might cause confusion: It is certainly possible that Adobe and Apple as well do some of this grouping already and achieves a good result, but it is still not perfect. The PDF I just tested was pretty mangled up after extracting the text via the Mac Preview.

Is there some good documentation about PDF Parsing in Swift?

You can use the CGPDFScanner, it's available on both Objective-C and Swift. Here is the documentation:

https://developer.apple.com/library/prerelease/ios/documentation/GraphicsImaging/Reference/CGPDFScanner/index.html

swift CGPDFDocument parsing

Your parsing retrieving high level dictionary and info data is correct, but you need to expand the decoding in CGPDFDictionaryApplyFunction to display the values of PDF data according their types (integer, string, array, dictionary, and so on). The syntax of the CGPDFDictionaryApplierFunction you are calling is:

typealias CGPDFDictionaryApplierFunction = (UnsafePointer<Int8>, COpaquePointer, UnsafeMutablePointer<()>) -> Void

Your program is displaying the pointers to the data, you could access the data values according their types as below (Swift 2):

    let filepath = "/Users/ben/Desktop/Test.pdf"
    let urlDocument = NSURL(fileURLWithPath: filepath)
    let myDocument = CGPDFDocumentCreateWithURL(urlDocument)
    if myDocument != nil {
        let numPages = CGPDFDocumentGetNumberOfPages(myDocument)
        print("Number of pages: \(numPages)")
        // Get complete catalog
        let myCatalog = CGPDFDocumentGetCatalog(myDocument)
        CGPDFDictionaryApplyFunction(myCatalog, printPDFKeys, nil)
        let myInfo = CGPDFDocumentGetInfo(myDocument)
        CGPDFDictionaryApplyFunction(myInfo, printPDFKeys, nil)
    } else {
        print("Cannot open PDF document")
    }

In order to be called from the CGPDFDictionaryApplyFunction, the printPDFKeys is to be called as a global function (outside your main class), alternately you could insert the code in a closure of CGPDFDictionaryApplyFunction as in your example above. The below code is shortened and is not including complete protection against errors and null values.

func printPDFKeys( key: UnsafePointer<Int8>, object: COpaquePointer, info: UnsafeMutablePointer<()>) {
    let contentDict: CGPDFDictionaryRef = CGPDFDictionaryRef(info)
    let keyString = String(CString: UnsafePointer<CChar>(key), encoding: NSISOLatin1StringEncoding)
    let objectType = CGPDFObjectGetType(object)
    if keyString == nil {
        return
    }
    print("key \(keyString!) is present in dictionary, type \(objectType.rawValue)")
    var ptrObjectValue = UnsafePointer<Int8>()
    switch objectType {
    // ObjectType is enum of:
    //   Null
    //   Boolean
    //   Integer
    //   Real
    //   Name
    //   String
    //   Array
    //   Dictionary
    //   Stream
    case .Boolean:
        // Boolean
        var objectBoolean = CGPDFBoolean()
        if CGPDFObjectGetValue(object, objectType, &objectBoolean) {
            let testbool = NSNumber(unsignedChar: objectBoolean)
            print("Boolean value \(testbool)")
        }
    case .Integer:
        // Integer
        var objectInteger = CGPDFInteger()
        if CGPDFObjectGetValue(object, objectType, &objectInteger) {
            print("Integer value \(objectInteger)")
        }
    case .Real:
        // Real
        var objectReal = CGPDFReal()
        if CGPDFObjectGetValue(object, objectType, &objectReal) {
            print("Real value \(objectReal)")
        }
    case .Name:
        // Name
        if (CGPDFObjectGetValue(object, objectType, &ptrObjectValue)) {
            let stringName = String(CString: UnsafePointer<CChar>(ptrObjectValue), encoding: NSISOLatin1StringEncoding)
            print("Name value: \(stringName!)")
        }
    case .String:
        // String
        let valueFound = CGPDFObjectGetValue(object, objectType, &ptrObjectValue)
        let stringValue = CGPDFStringCopyTextString(COpaquePointer(ptrObjectValue))
        print("String value: \(stringValue!)")
    case .Array:
        // Array
        print("Array")
        var objectArray = CGPDFArrayRef()
        if (CGPDFObjectGetValue(object, objectType, &objectArray))
        {
            print("array: \(arrayFromPDFArray(objectArray))")
        }
    case .Dictionary:
        // Dictionary
        var objectDictionary = CGPDFDictionaryRef()
        if (CGPDFObjectGetValue(object, objectType, &objectDictionary)) {
            let count = CGPDFDictionaryGetCount(objectDictionary)
            print("Found dictionary with \(count) entries")
            if !(keyString == "Parent") && !(keyString == "P") {
                //catalogLevel = catalogLevel + 1
                CGPDFDictionaryApplyFunction(objectDictionary, printPDFKeys, nil)
                //catalogLevel = catalogLevel - 1
            }
        }
case .Stream:
    // Stream
    print("Stream")
    var objectStream = CGPDFStreamRef()
    if (CGPDFObjectGetValue(object, objectType, &objectStream)) {
        let dict: CGPDFDictionaryRef = CGPDFStreamGetDictionary( objectStream )
        var fmt: CGPDFDataFormat = .Raw
        let streamData: CFDataRef = CGPDFStreamCopyData(objectStream, &fmt)!;
        let data = NSData(data: streamData)
        let dataString = NSString(data: data, encoding: NSUTF8StringEncoding)
        let dataLength: Int = CFDataGetLength(streamData)
        print("data stream (length=\(dataLength)):")
        if dataLength < 400 {
            print(dataString)
        }
    }
default:
    print("Null")
}
}

// convert a PDF array into an objC one
func arrayFromPDFArray(pdfArray: CGPDFArrayRef ) -> NSMutableArray {
var i:Int = 0
var tmpArray: NSMutableArray = NSMutableArray()

let count = CGPDFArrayGetCount(pdfArray)
for i in 0..<count {
    var value = CGPDFObjectRef()
    if (CGPDFArrayGetObject(pdfArray, i, &value)) {
        if let object = objectForPDFObject(value) {
            tmpArray.addObject(object)
        }
    }
}

return tmpArray
}

func objectForPDFObject( object: CGPDFObjectRef) -> AnyObject? {
let objectType: CGPDFObjectType = CGPDFObjectGetType(object)
var ptrObjectValue = UnsafePointer<Int8>()
switch (objectType) {
case .Boolean:
    // Boolean
    var objectBoolean = CGPDFBoolean()
    if CGPDFObjectGetValue(object, objectType, &objectBoolean) {
        let testbool = NSNumber(unsignedChar: objectBoolean)
        return testbool
    }
case .Integer:
    // Integer
    var objectInteger = CGPDFInteger()
    if CGPDFObjectGetValue(object, objectType, &objectInteger) {
        return objectInteger
    }
case .Real:
    // Real
    var objectReal = CGPDFReal()
    if CGPDFObjectGetValue(object, objectType, &objectReal) {
        return objectReal
    }
case .String:
    let valueFound = CGPDFObjectGetValue(object, objectType, &ptrObjectValue)
    let stringValue = CGPDFStringCopyTextString(COpaquePointer(ptrObjectValue))
    return stringValue
case .Dictionary:
    // Dictionary
    var objectDictionary = CGPDFDictionaryRef()
    if (CGPDFObjectGetValue(object, objectType, &objectDictionary)) {
        let count = CGPDFDictionaryGetCount(objectDictionary)
        print("In array, found dictionary with \(count) entries")
        CGPDFDictionaryApplyFunction(objectDictionary, printPDFKeys, nil)
    }
case .Stream:
    // Stream
    var objectStream = CGPDFStreamRef()
    if (CGPDFObjectGetValue(object, objectType, &objectStream)) {
        let dict: CGPDFDictionaryRef = CGPDFStreamGetDictionary( objectStream )
        var fmt: CGPDFDataFormat = .Raw
        let streamData: CFDataRef = CGPDFStreamCopyData(objectStream, &fmt)!;
        let data = NSData(data: streamData)
        let dataString = NSString(data: data, encoding: NSUTF8StringEncoding)
        print("data stream (length=\(CFDataGetLength(streamData))):")
        return dataString
    }
default:
    return nil
}
return nil
}

Read contents of pdf as string

If you want to avoid a lot of programming, you probably need to use some library which will help you extract text from PDFs.

You have two options:

1) Use OCR library. Since PDF can contain images besides text, performing OCR to get the text is the most generic solution. To perform OCR on a PDF document, you need to convert it to UIImage object. Another approach can be to convert contents of the WebView to UIImage, but this might result with image with lower resolution, which can affect OCR performance.

The downside to using OCR library is that you will not get 100% accurate text, since the OCR engine always introduces errors.

The best options for OCR are Tesseract for iOS (free, but with higher error rate and a bit more complex to tweak for results). A more robust option is BlinkOCR, which is free to try, paid when in commercial use, but you can get a ton of help from their engineers.

2) You can also use PDF library. PDF libraries can reliably extract text written in the document, with exception of text which is part of the images inside the PDF. So depending on the documents you want to read this might be a better option (or not).

Some options for PDF libraries can be found here, and in our experience, PDFlib gives very good results and is the most customizable.

Converting a PDF image to NSData for Parse.com in Swift

Use this code for myData:

var pdfPath = documentsPath.stringByAppendingPathComponent("test.pdf")
var PDFUrl = NSURL(string: pdfPath)            //convert pdfPath string to NSURL
var myData = NSData(contentsOfURL: PDFUrl!)