In my previous post on pdfMiner, I wrote on how to extract information from a pdf. For completeness, I will discuss how PyPDF2 and reportlab can be used to write a pdf and manipulate an existing pdf. I am learning as I go here. This is some low hanging fruit meant to provide a fuller picture. Also, I am quite busy.
PyPDF and reportlab do not offer the completeness in extraction that pdfMiner offers. However, they offer a way of writing to existing pdfs and reportlab allows for document creation. For Java, try PDFBox.
However, PyPdf is becoming extinct and pyPDF2 has broken pages on its website. The packages are still available from pip,easy_install, and from github. The mixture of reportlab and pypdf is a bit bizzare.
PyPdf, unlike pdfMiner, is well documented. The author of the original PyPdf also wrote an in depth review with code samples. If you are looking for an in depth manual for use of the tool, it is best to start there.
Report Lab Documentation
Report lab documentation is available to build from the bitbucket repositories.
Installing PyPdf and ReportLab
easy_install pypdf2 pip install pypdf2 easy_install reportlab pip install reportlab
The necessary part of report lab is the canvas objects. Report lab has several sizes. They are letter,legal, and portrait. The canvas object is instantiated with a string and size.
from reportlab.pdfgen import canvas from reportlab.lib.pagesizes import portrait
PyPdf2 has a relatively simple setup. A PdfFileWriter is initialized to add to the document, as opposed to the PdfReader which reads from the document. The reader takes a file object as its parameter. The writer takes an output file at write time.
from pyPDF2 import PdfFileWriter, PdfFileReader # a reader reader=PdfFileReader(open("fpath",'rb')) # a writer writer=PdfFileWriter() outfp=open("outpath",'wb') writer.write(outfp)
All of this can be found under the review by the writer of the original pyPdf.
Working with PyPdf2 Pages and Objects
Before writing to a pdf, it is useful to know how to create the structure and add objects. With the PdfFileWriter, it is possible to use the following methods (an IDE or the documentation will give more depth).
- addBlankPage-create a new page
- addBookmark-add a bookmark to the pdf
- addLink- add a link in a specific rectangular area
- addMetaData- add meta data to the pdf
- insertPage-adds a page at a specific index
- insertBlankPage-insert a blank page at a specific index
- addNamedDestination-add a named destination object to the page
- addNamedDestinationObject-add a created named destination to the page
- encrypt-encrypt the pdf (setting use_128bit to True creates 128 bit encryption and False creates 40 bit encryption with a default of 128 bits)
- removeLinks-removes links by object
- removeText-removes text by text object
- setPageMode-set the page mode (e.g. /FullScreen,/UseOutlines,/UseThumbs,/UseNone
- setPageLayout-set the layout(e.g. /NoLayout,/SinglePage,/OneColumn,/TwoColumnLeft)
- getPage-get a page by index
- getLayout-get the layout
- getPageMode-get the page mode
- getOutlineRoot-get the root outline
Report lab also contains a set of objects. Documentation can be found here. It appears that postscript or something similar is used for writing documents to a page in report lab. Using ghostscript, it is possible to learn postscript. Postscript is like assembler and involves manipulating a stack to create a page. It was developed at least in part by Adobe Systems, Inc. back in the 1980s and before my time on earth began.
Some canvas methods are:
- addFont-add a font object
- addOutlineEntry-add an outline type to the pdf
- addPostscriptCommand-add postscript to the document
- addPageLabel-add a page label to the document canvas
- arc-draw an arc in a postscript like manner
- beginText-create a text element
- bezier-create a postscript like bezier curve
- drawString-draw a string
- drawText-draw a text object
- drawPath-darw a postscript like path
- drawAlignedString-draw a string on a pivot character
- drawImage-draw an image
- ellipse-draw an elipse on a bounding box
- circle-draw a circle
- rect-draw a rectangle
Write a String to a PDF
There are two things that dominate the way of writing pdf files, writing images, and writing strings to the document. This is handled entirely in
Here, I have added some text and a circle to a pdf.
def writeString(): fpath="C:/Users/andy/Documents/temp.pdf" packet = StringIO.StringIO() packet=StringIO.StringIO() cv=canvas.Canvas(packet, pagesize=letter) #create a string cv.drawString(0, 500, "Hello World!") #a circle. Do not add another string. This draws on a new page. cv.circle(50, 250, 20, stroke=1, fill=0) #save to string cv.save() #get back to 0 packet.seek(0) #write to a file with open(fpath,'wb') as fp: fp.write(packet.getvalue())
Unfortunately, adding a new element occurs on a new page after calling the canvas’ save method. Luckily the “closure” of the pdf just creates a new page object. A much larger slice of documentation by reportlab goes over writing a document in more detail. The documentation includes alignment and other factors. Alignments are provided when adding an object to a page.
Manipulating a PDF
Manipulation can occur with ReportLab. ReportLab allows for deletion of pages,insertion of pages, and creation of blank pages. The author of pyPDF goes over this in depth in his review.
This code repeats the previous pages twice in a new pdf. It is also possible to merge (overlay) pdf pages.
from PyPDF2 import PdfFileWriter,PdfFileReader pdf1=PdfFileReader(open("C:/Users/andy/Documents/temp.pdf")) pdf2=PdfFileReader(open("C:/Users/andy/Documents/temp.pdf")) writer = PdfFileWriter() # add the page to itself for i in range(0,pdf1.getNumPages()): writer.addPage(pdf1.getPage(i)) for i in range(0,pdf2.getNumPages()): writer.addPage(pdf2.getPage(i)) # write to file with file("destination.pdf", "wb") as outfp: writer.write(outfp)
Overall, PyPDF is useful for merging and changing existing documents in terms of the the way they look and reportlab is useful in creating documents from scratch. PyPDF deals mainly with the objects quickly and effectively and reportlab allows for in depth pdf creation. In combination, these tools rival others such as Java’s PdfBox and even exceed it in ways. However, pdfMiner is a better extraction tool.