Swift: NSMutableAttributedString generated from PDF. Can it be parsed into a Dictionary?

Question

I have several large PDF docs (70-200, pages each). The PDFs themselves are generated from HTML pages (I can't get the source code of the HTML pages which is why I am working with the PDFs). Anyway, what I want to do is parse the PDF into separate pages based on the converted H1 tag attribute. When I print out the PDF I get this:

Seller Tag (AST)
{
NSBaselineOffset = 0;
NSColor = "Device RGB colorspace 0.94118 0.32549 0.29804 1";
NSFont = "\"Helvetica 8.00 pt. P [] (0x7ff0f262e590) fobj=0x7ff0f4339680, spc=2.22\"";
}Table of Contents
{
NSBaselineOffset = 0;
NSColor = "Device RGB colorspace 0.94118 0.32549 0.29804 1";
NSFont = "\"Helvetica 34.00 pt. P [] (0x7ff0f262e590) fobj=0x7ff0f432f940, spc=9.45\"";
}...

which looks like a bunch of attributes contained in a Dictionary. But when I run this code:

 let strContent = myAppManager.pdfToText(fromPDF:pdfDirPath.absoluteString + "/" + thisFile)
 let strPDF:NSAttributedString = strContent
 let strNSPDF = strPDF.string as NSString
 let rangeOfString = NSMakeRange(0, strNSPDF.length)
 let arrAttributes = strPDF.attributes(at: 0, longestEffectiveRange: nil, in: rangeOfString)
 print(arrAttributes)

I get this output

[__C.NSAttributedStringKey(_rawValue: NSColor): Device RGB colorspace 0.94118 0.32549 0.29804 1, __C.NSAttributedStringKey(_rawValue: NSBaselineOffset): 0, __C.NSAttributedStringKey(_rawValue: NSFont): "Helvetica 8.00 pt. P [] (0x7ff0f441d490) fobj=0x7ff0f4339680, spc=2.22"]

I was kind of expecting a high number, like 1000 or more entries, not 1.

So snooping around, I know the H1 HTML tag gets converted to this:

Table of Contents
{
NSBaselineOffset = 0;
NSColor = "Device RGB colorspace 0.94118 0.32549 0.29804 1";
NSFont = "\"Helvetica 34.00 pt. P [] (0x7ff0f262e590) fobj=0x7ff0f432f940, spc=9.45\"";
}

So what I am looking to do is delimit the converted H1s so I can get the content between as a page and do stuff with it. Any ideas or suggestions would be appreciated.

Answer 1

Quickly done, assuming you have:

someText[HEADER1]someText1[HEADER2]someText2[HEADER3]someText3...

Where [HEADERN] have the same attributes (and you know them) but not the same as someTextN.

We want in the end, and array of:

struct Page: CustomStringConvertible {
    let title: NSAttributedString? //Tha's be the h1 tag content
    let content: NSAttributedString?

    var description: String {
        return "Title: \(title?.string ?? "") - content: \(content?.string ?? "")"
    }
}

Initial sample:

let htmlString = "<b>Title 1</b> Text for part one.\n <b>Title 2</b> Text for part two<b>Title 3</b>Text for part three"
let attributedString = try! NSAttributedString(data: Data(htmlString.utf8),
                                               options: [.documentType : NSAttributedString.DocumentType.html],
                                               documentAttributes: nil)

With:

let headerAttributes: [NSAttributedString.Key: Any] = [.font: UIFont.boldSystemFont(ofSize: 12)]
print("headerAttributes: \(headerAttributes)")

func headerOneAttributes(_ headerAttributes: [NSAttributedString.Key: Any], matches attributes: [NSAttributedString.Key: Any]?) -> Bool {
    guard let attributes = attributes else { return false }

    guard let attributesFont = attributes[.font] as? NSFont, let headerFont = headerAttributes[.font] as? NSFont else {
        return false
    }
    return attributesFont.fontDescriptor.symbolicTraits == NSFontDescriptor.SymbolicTraits(rawValue: 268435458) //Here fonts arent' equal equal, some work here plus checking on other attributes too and font size?
    // Do you own check
    // return false
}

We can iterates the attributes to get all the headers ranges:

var headerRanges: [NSRange] = []
attributedString.enumerateAttributes(in: NSRange(location: 0, length: attributedString.length), options: []) { attributes, range, stop in
    if headerOneAttributes(headerAttributes, matches: attributes) {
        headerRanges.append(range)
    }
}

With an iteration on the ranges:

var pages: [Page] = []
guard !headerRanges.isEmpty else { return }

//In case the first title doesn't "start at the beginning", we have a "content" with no title at start
if let first = headerRanges.first, first.location > 0 {
    pages.append(Page(title: nil, content: attributedString.attributedSubstring(from: first)))
}

// Then we iterate
for (anIndex, aRange) in headerRanges.enumerated() {
    print(pages)
    let title = attributedString.attributedSubstring(from: aRange)
    let subtext: NSAttributedString?
    // If there is a "nextRange", then we get the end of subtext from it
    if anIndex + 1 <= headerRanges.count - 1 {
        let next = headerRanges[anIndex + 1]
        let location = aRange.location + aRange.length
        let length = next.location - location
        subtext = attributedString.attributedSubstring(from: NSRange(location: location, length: length))
    } else {
        //There is no next => Until the end
        let location = aRange.location + aRange.length
        let length = attributedString.length - location
        subtext = attributedString.attributedSubstring(from: NSRange(location: location, length: length))
    }
    pages.append(Page(title:title, content: subtext))
}
print(pages)

PS: UIFont/NSFont: ~the same, I tested on a macOS app, not iOS, that's why.

Answer 2

Okay, so @Larme put me on the right track for what I was looking for. Posting the code in hopes it helps someone else. I've tested this on a 77 page document and it worked. I should have noted in the question that I am working on MacOS.

func parsePDF(_ strPDFContent:NSMutableAttributedString) -> Array<Dictionary<String, Any>> {
    
    //some initial setup
    let strNSPDF = strPDFContent.string as NSString
    var arrDocSet:Array<Dictionary<String, Any>> = []
    
    //get all the page headers
    var arrRanges = [NSRange]()
    strPDFContent.enumerateAttribute(NSAttributedString.Key.font, in: NSRange(0..<strPDFContent.length), options: .longestEffectiveRangeNotRequired) {
        value, range, stop in
        if let thisFont = value as? NSFont {
            if thisFont.pointSize == 34 {
                arrRanges.append(range)
            }
        }
    }
    
    //get the content and store data
    for (idx, range) in arrRanges.enumerated() {
        
        //get title
        let strTitle = String(strNSPDF.substring(with: range))
        var textRange = NSRange(location:0, length:0)
        
        //skip opening junk
        if !strTitle.contains("Table of Contents\n") {
            
            if idx < arrRanges.count-1 {
                textRange = NSRange(location: range.upperBound, length: arrRanges[idx+1].lowerBound - range.upperBound)
            } else if idx == arrRanges.count-1 {
                textRange = NSRange(location: range.upperBound, length: strNSPDF.length - range.upperBound)
            }
        
            let strContent = String(strNSPDF.substring(with: textRange))

            arrDocSet.append(["title":strTitle, "content":strContent, "contentRange":textRange, "titleRange":range])
            
        }
            
    }
    
    print(arrDocSet)
    
    return arrDocSet
    
}

This will output:

["titleRange": {10001, 27}, "title": "Set up Placements with AST\n", "content": "This page contains a sample web page showing how Xandr\'s seller tag (AST) functions can be implemented in the header and body of a sample client page.\nSee AST API Reference for more details on using ...
...
ready.\nExample\n$sf.ext.status();\n", "title": " SafeFrame API Reference\n", "contentRange": {16930, 9841}

Let me know if there's places I could be more efficient.