Extract Text Using PdfMiner and PyPDF2 Merges columns

Question

I am trying to parse the pdf file text using pdfMiner, but the extracted text gets merged. I am using the pdf file from the following link.

PDF File

I am good with any type of output (file/string). Here is the code which returns the extracted text as string for me but for some reason, columns are merged.

from pdfminer.converter import TextConverter
from pdfminer.layout import LAParams
from pdfminer.pdfinterp import PDFResourceManager, process_pdf
import StringIO

def convert_pdf(filename):
    rsrcmgr = PDFResourceManager()
    retstr = StringIO()
    codec = 'utf-8'
    laparams = LAParams()
    device = TextConverter(rsrcmgr, retstr, codec=codec)

    fp = file(filename, 'rb')
    process_pdf(rsrcmgr, device, fp)
    fp.close()
    device.close()

    str = retstr.getvalue()
    retstr.close()
    return str

I have also tried PyPdf2, but faced the same issue. Here is the sample code for PyPDF2

from PyPDF2.pdf import PdfFileReader
import StringIO
import time

def getDataUsingPyPdf2(filename):
    pdf = PdfFileReader(open(filename, "rb"))
    content = ""

    for i in range(0, pdf.getNumPages()):
        print str(i)
        extractedText = pdf.getPage(i).extractText()
        content +=  extractedText + "\n"

    content = " ".join(content.replace("\xa0", " ").strip().split())
    return content.encode("ascii", "ignore")

I have also tried pdf2txt.py but unable to get the formatted output.

Answer 1

I recently struggled with a similar problem, although my pdf had slightly simpler structure.

PDFMiner uses classes called "devices" to parse the pages in a pdf fil. The basic device class is the PDFPageAggregator class, which simply parses the text boxes in the file. The converter classes , e.g. TextConverter, XMLConverter, and HTMLConverter also output the result in a file (or in a string stream as in your example) and do some more elaborate parsing for the contents.

The problem with TextConverter (and PDFPageAggregator) is that they don't recurse deep enough to the structure of the document to properly extract the different columns. The two other converters require some information about the structure of the document for display purposes, so they gather more detailed data. In your example pdf both of the simplistic devices only parse (roughly) the entire text box containing the columns, which makes it impossible (or at least very difficult) to correctly separate the different rows. The solution to this that I found works pretty well, is to either

• Create a new class that inherits from PDFPageAggregator, or
• Use XMLConverter and parse the resulting XML document using e.g. Beautifulsoup

In both cases you would have to combine the different text segments to rows using their bounding box y-coordinates.

In the case of a new device class ('tis more eloquent, I think) you would have to override the method receive_layout that get's called for each page during the rendering process. This method then recursively parses the elements in each page. For example, something like this might get you started:

from pdfminer.pdfdocument import PDFDocument, PDFNoOutlines
from pdfminer.pdfparser import PDFParser
from pdfminer.pdfinterp import PDFResourceManager, PDFPageInterpreter
from pdfminer.converter import PDFPageAggregator
from pdfminer.layout import LTPage, LTChar, LTAnno, LAParams, LTTextBox, LTTextLine

class PDFPageDetailedAggregator(PDFPageAggregator):
    def __init__(self, rsrcmgr, pageno=1, laparams=None):
        PDFPageAggregator.__init__(self, rsrcmgr, pageno=pageno, laparams=laparams)
        self.rows = []
        self.page_number = 0
    def receive_layout(self, ltpage):        
        def render(item, page_number):
            if isinstance(item, LTPage) or isinstance(item, LTTextBox):
                for child in item:
                    render(child, page_number)
            elif isinstance(item, LTTextLine):
                child_str = ''
                for child in item:
                    if isinstance(child, (LTChar, LTAnno)):
                        child_str += child.get_text()
                child_str = ' '.join(child_str.split()).strip()
                if child_str:
                    row = (page_number, item.bbox[0], item.bbox[1], item.bbox[2], item.bbox[3], child_str) # bbox == (x1, y1, x2, y2)
                    self.rows.append(row)
                for child in item:
                    render(child, page_number)
            return
        render(ltpage, self.page_number)
        self.page_number += 1
        self.rows = sorted(self.rows, key = lambda x: (x[0], -x[2]))
        self.result = ltpage

In the code above, each found LTTextLine element is stored in an ordered list of tuples containing the page number, coordinates of the bounding box, and the text contained in that particular element. You would then do something similar to this:

from pprint import pprint
from pdfminer.pdfparser import PDFParser
from pdfminer.pdfdocument import PDFDocument
from pdfminer.pdfpage import PDFPage
from pdfminer.pdfinterp import PDFResourceManager, PDFPageInterpreter
from pdfminer.layout import LAParams

fp = open('pdf_doc.pdf', 'rb')
parser = PDFParser(fp)
doc = PDFDocument(parser)
doc.initialize('password') # leave empty for no password

rsrcmgr = PDFResourceManager()
laparams = LAParams()
device = PDFPageDetailedAggregator(rsrcmgr, laparams=laparams)
interpreter = PDFPageInterpreter(rsrcmgr, device)

for page in PDFPage.create_pages(doc):
    interpreter.process_page(page)
    # receive the LTPage object for this page
    device.get_result()

pprint(device.rows)

The variable device.rows contains the ordered list with all the text lines arranged using their page number and y-coordinates. You can loop over the text lines and group lines with the same y-coordinates to form the rows, store the column data etc.

I tried to parse your pdf using the above code and the columns are mostly parsed correctly. However, some of the columns are so close together that the default PDFMiner heuristics fail to separate them into their own elements. You can probably get around this by tweaking the word margin parameter (the -W flag in the command line tool pdf2text.py). In any case, you might want to read through the (poorly documented) PDFMiner API as well as browse through the source code of PDFMiner, which you can obtain from github. (Alas, I cannot paste the link because I do not have sufficient rep points :'<, but you can hopefully google the correct repo)