How can I parse content from a PDF page with Swift

user_5417088 0
Viewed 3738

The documentation is not really clear to me. So far I reckon I need to set up a CGPDFOperatorTable and then create a CGPDFContentStreamCreateWithPage and CGPDFScannerCreate per PDF page.

The documentation refers to setting up Callbacks, but it's unclear to me how. How to actually obtain the content from a page?

This is my code so far.

    let pdfURL = NSBundle.mainBundle().URLForResource("titleofdocument", withExtension: "pdf")

    // Create pdf document
    let pdfDoc = CGPDFDocumentCreateWithURL(pdfURL)

    // Nr of pages in this PF
    let numberOfPages = CGPDFDocumentGetNumberOfPages(pdfDoc) as Int

    if numberOfPages <= 0 {
        // The number of pages is zero
        return
    }

    let myTable = CGPDFOperatorTableCreate()

    // lets go through every page
    for pageNr in 1...numberOfPages {

        let thisPage = CGPDFDocumentGetPage(pdfDoc, pageNr)
        let myContentStream = CGPDFContentStreamCreateWithPage(thisPage)
        let myScanner = CGPDFScannerCreate(myContentStream, myTable, nil)

        CGPDFScannerScan(myScanner)

        // Search for Content here?
        // ??

        CGPDFScannerRelease(myScanner)
        CGPDFContentStreamRelease(myContentStream)

    }

    // Release Table
    CGPDFOperatorTableRelease(myTable)

It's a similar question to: PDF Parsing with SWIFT but has no answers yet.

swift pdf parsing ios
3 Answers

To understand why a parser works this way, you need to read the PDF specification a bit better. A PDF file contains something close to printing instructions. Such as "move to this coordinate, print this character, move there, change the color, print the character number 23 from the font #23", etc.

The parser gives you callbacks for each instructions, with the possibility to retrieve the instruction parameters. That's all.

So, in order to get the content from a file, you need to rebuild its state manually. Which means, recompute the frames for all characters, and try to reverse-engineer the page layout. This is clearly not an easy task, and that's why people have created libraries to do so.

You may want to have a look at PDFKitten , or PDFParser which is a Swift port with some improvement that i did.

user_1944700
Related