I wasn't able to find anything on the internet and I get the feeling that what I want is not such a trivial thing. To make a long story short: I'd like to get my hands on the underlying code that describes the PDF document of a selected area from a .pdf file. I've been looking for libraries or open source readers but couldn't find anything useful yet.
Does there exist something that might be able to accomplish my needs here or anything that might be reused (like an open source reader) to get there a little faster and not having to write everything from scratch?
You can convert a whole PDF document to PostScript using pdftops, one of the utilities from the poppler PDF rendering library.
This utility enables you to convert individual pages, which is at least a start.
If you just want to extract bitmapped images, try pdfimages from the same package. This extraction can also be restricted to individual pages.
The poppler library was originally written for UNIX-like systems, but there are a couple of windows builds available.
The open source tool from iText called iText RUPS does what you want, showing you all the PDF commands for a particular PDF and allow you to visualize the structure and relationships.
http://sourceforge.net/projects/itextrups/
Related
I have to extract text from invoices and bills pdf files
The files layouts can get complex, though its mostly filled with tables.
I've read a few dozens articles already about the pdf format, how easy it is for our brain to grasp it and how hard it is for a machine to understand its structure.
Also downloaded a few tools like the python's pdfminer and some java tools, some even have rule based layout extraction, like LA-PDBtext these are all great libraries, leaving you the final step.
Adobe also has an online service called exportPdf but it can't be customized
Bottom line, I understand that in order to extract text from structured pdf files and convert it to XML for example, there should be some level of manual work.
I also found From Data Extractor, a non free tool with the ability to set extraction rules that claims to do the job, though its hard to find a proper manual and it runs only on windows.
I thought I may even try a to convert those files to images and try tesseract-ocr but decided to ask for advice here before I spend more time on it.
I'll be very grateful if someone with such experience give me a hint.
I've done a lot of PDF extraction and I can confirm as you've already discovered that it can be a painful process to start. One of the important things to understand is that there is no concept of "tables" within a PDF, just text that happens to have lines around it. Also, there's no guarantee that the linear order of text within the PDF code actually matches the visual order when printed. In other words, there's no guarantee that "hello world" is written in that order, it could be draw 'word' at coord 20 then draw 'hello' at coord 10. Most PDF creators don't do this but still there's no guarantee. The more creative a PDF creator is (InDesign, Illustrator, etc) the more likely the text is going to be harder to get out. And actually, once a designer starts messing with fonts too much some programs will sometimes actually output words one character at a time, changing the font just slightly each time.
That said, I'd recommend the first one that you looked at, LA-PDFText. You can run it in discovery mode (blockify) from which you can create rules. I don't have Java installed anymore so I can't test it but it seems very promising.
Your second one, A-PDF Form Data Extractor, only really works with actual PDF forms. If this is your case I'd recommend just using an open source solution like iText/iTextSharp.
The last OCR one makes me cringe. I just can't imagine going through those hoops would get you better text representation than parsing the PDF. But then again, PDF is a visual format so maybe it would.
Personally I use iText/iTextSharp for this kind of thing but I also like to do things the hard way.
It is not clear if you are looking for the development tool to automate the data extraction from bills and invoices or just for the one time tool (utility) that can be used by the non-developer?
Anyway here are some specialized tools including engines they use:
Tabula (open-source, especially designed to extract data from tables in PDF. Can export shell scripts for batch processing, runs as the localhost web service, powered by JRuby Tabula engine)
Viet OCR (open-source .NET desktop utility for text extraction from PDF and images, based on tesseract oct engine)
Bytescout PDF Viewer (freeware closed source .NET utility, detects and extracts tables, including scanned invoices, powered by PDF Extractor SDK)
DISCLAIMER: I work for ByteScout.
I want to download a pdf file progressively in an iPad application. I m not sure how to do that and google wasn't very helpful. can anyone help me understand the concepts here please. I am planning to render in core graphics.
Thanks.
Do you mean you want to render pdf pages before download is completed? If yes:
First of all, PDF format initially was not designed for that.
Let me explain. PDF file consists of a number of objects and xref. xref is a table containing location (in bytes from the beginning) of every object withing the file, so objects may be located at random locations withing the file. Even worse, xref itself is located at the end of file, so you can't locate any object in the file until you download it.
So, PDF is designed for random access. Actually, HTTP protocol allows it, so if you really need it, you can try to implement it :)
Good news for you: starting from PDF-1.2 there is a special feature called "Linearized PDF". It is designed exactly for your task, so you can render the first page before the next one if downloaded. You can google around or check out pdf reference for more details. The most important thing: you have to linearize pdf file using special tools, so not every pdf file can be rendered progressively.
Bad news for you: looks like core graphics doesn't support. I didn't tried it actually, but I found nothing re linearized pdf in core graphics documentation. (Please let me know if you will find anything.) So you may need to render PDF manually.
Not entirely sure about for iPad, but doing a Save as... in Acrobat by default it will be optimized as Fast Web View, which allows downloads a page at a time instead of the whole document in one go.
http://www.adobe.com/designcenter-archive/acrobat/articles/acr6optimize/acr6optimize.pdf
Linearzied PDF will meet your needs. You need a capable reader such as the one from Adobe to utilize this feature.
I've been working on an app to create various document formats for a while now, and I've had limited success.
Ideally, I'd like to dynamically create a fairly simple ODT/PDF/DOC file. I've been focusing my efforts on ODT, because it is editable, and open enough that there are several tools which will convert it to any of the other formats I need.
The problem is that the ODT XML files are NOT simple, and there aren't any good-quality API's I could find (especially in python). So far, I've had the most success creating a template ODT file, and then manipulating the DOM in python as needed. This is ok generally, but is quickly becoming inadequate and requires too much tweaking every single time I need to alter one of the templates.
The requirements are:
1) Produce a simple document that will have lists, paragraphs, and the ability to draw simple graphics on the page (boxes, circles, etc...)
2) The ability to specify page size, and the different formats should generally print the exact same output when sent to a printer
My questions:
1) Are there any other ways I can produce ODT/PDF/DOC files?
2) Would LaTeX be acceptable? I've never really used it, does anyone have experience converting LaTeX files into other formats?
3) Would it be possible to use HTML? There are a lot of converters online. Technically you can specify dimensions in mm/cm, etc..., but I am worried that the printed output will differ between browsers/converters....
Any other ideas?
have you tried pandoc? i've been using it with good success for the conversion of different formats into each other. why try to invent the wheel twice?
I suppose to be successful, you'd have to define how you want to input everything. Why don't you just use openoffice? it will save to ODT (duh...), PDF, and HTML (though it's not clean HTML, it's actually quite ugly).
In my recent experience, I've had success going from latex -> xhtml via LaTeXML (i had to compile from source). LaTeX is seeming more and more like a terminal format. It's great for PDF, but once you need some flexibility, it kind of fails. I should also note that there is no latex -> dvi in my workflow, so I can't comment on things like tex4ht that reads out of a dvi file (I have too many graphics that don't work with DVI to switch them now).
Shortly I'll be moving everything into docbook 4.5-- i like the docbook-utils package which supports latex, html, and i even saw a converter to ODT. But docbook is super-heavy on the markup, which is annoying, but it will provide me with the flexibility i need going forward.
Since you're using python, have you just considered using ReStructured Text?
I've also really enjoyed publishing from emacs' orgmode, which is a super light weight markup that goes into a bunch of different formats.
Like the title says. Reason I ask is that we're converting PDFs to formatted ASCII text (using pdftotext) and only want to display the ones that look reasonably sane.
PPT files tend to have text over images, diagonal text and others things that don't translate to ASCII very well, so we'd like to filter them out if we can.
The creating application of a PDF is listed in its XMP metadata. You can see this quite easily in Acrobat 9 (and I believe earlier): go to File > Properties, click Additional Metadata..., then go to Advanced and it's listed under both XMP Core Properties and PDF Properties:
xmp:CreatorTool: Microsoft PowerPoint
pdf:Creator: Microsoft PowerPoint
I'm guessing you want to find this programatically, so you'll need to find a library to read this metadata that works with your language. Here is a list of some XMP tools.
Short answer:
No, I don't think so.
Long answer:
No, I don't think so, because there are may ways to convert a PowerPoint file to pdf, for example Adobe Acrobat and PDFCreator and many many others. It's up to the converters to embed specific information in the PDF file, even if you find a way to detect PowerPoint-source pdf from one convert, the same method may not work for another.
Even longer answer:
No, I don't think so, because of the reasons described in the "long answer". And I don't think detecting the source of the PDF is the best approach to the problem you are trying to solve. Not just PowerPoint produces overlapped text and images. I think it's much better to detect the actual layout of the PDF file. If there are overlay of image and text, then you do some filtering or pre-processing to cater for that.
Your reasoning is very arbitrary - there are surely plenty of PPT files without the features you describe, and plenty of PDF files with them, that were generated from another source.
In theory a better method would just be to detect when these "unwanted" situations occur. However, even though the PDF format is partly open (only for reading, apparently, so it's not truly an open format), extracting complex data like that would be incredibly difficult.
All PDFs can have this problem regardless of their source. Most desktop publishing suites are capable of outputting PDF and are often sold boasting their high quality and flashier PDF presentations ...
A "saner" method would be to use a PDF parser, ITextSharp, or pdfNet...etc, Using the library of your choice, find all image rectangles, and all text rectangles, SORT THE RECTANGLES, and then see if there is substantial overlap of text and image rects -- ignoring image to image overlaps. If so, reject the page and/or document.
That won't be perfect, but at least it's going to catch many PDFs that aren't sane, regardless of source. Other heuristics to add would include color analysis. (i.e. are the colors in the overlapping region sufficiently different to allow "sane" results?)
Best of luck to you
It might put its name in the creator or producer info, but I don't have a copy to check this theory with.
In general, it is not an easy task to programmatically determine (reliably) where a file came from or how it was generated based on its contents. After all, a file is just a collection of bits.
Unless you have a lot of resources to expend building the heuristics to determine whether a file looks "reasonably sane" according to your needs, I would consider this a task for human beings.
some converter from ppt to pdf preserve creator in comments at begin of pdf.
I think that PDF's generated from most applications seem to be the same. It may have some meta-data that you can read from the file...
I'd like to write some (java) code that takes a PDF document, and creates named destinations from all of the bookmarks. I think the iText API is the easiest way of doing this, but I have never used the API before.
How would you go about writing this sort of code with the iText API? Can iText do the parsing needed to manipulate existing PDFs by itself? The kind of manipulations I am thinking of are:
Open,
Find bookmarks,
Create destinations,
Save,
Close.
Or is there a different API that would be better?
Followup: I submitted a patch to iText a few months ago (it has now been accepted and is part of HEAD) that adds text parsing capabilities to iText. PdfBox (mentioned below) has (had?) problems with reading newer PDFs that use xref streams instead of the older xref table format.
Another library that is very good at parsing existing PDF files is PdfBox It can also be used for modifying an existing PDF. FYI - this is the text parser that Lucene uses.
I will also mention that iText does have the ability to parse a PDF file, it's just not great at parsing the text content on each page. If you are looking at accessing the PDF higher level constructs (Dictionaries, etc...) that are used for storing bookmarks, etc... and you don't mind getting your hands a little dirty with reading the PDF spec, you can absolutely do what you are asking about (we do it quite a bit ourselves).
The PDF Spec is big, but readable for the most part, and you don't have to worry about the bulk of it (which is geared towards actual page content and rendering) if all you are trying to do is extract bookmarks.
I'll just warn you up front that you may be disappointed with this. iText isn't really intended to be used as a parser. It's really more for creating entirely new PDF documents, but you can take a whack at it.
To start, using iText, you won't be able to modify the existing PDF document. What you can do, though, is to make a copy with the additional features that you want. (If somebody else knows better, please let me know, this drives me crazy.)
What you will want to do is create a PdfReader object from an input stream on your source file. Then create a PdfCopy object (which is just an extended PdfWriter that makes getting data from an existing source more convenient) for your destination.
As far as I can tell, the bookmarks cannot be obtained from iText at all. Another library may be needed. I think jpedal may have the ability to extract them (it can get them as an XML document, which you may then have to parse to get what you want.) However you get them, you can then add them to a java.util.List, and set that list as outline on the PDFCopy. The bookmarks themselves are just HashMaps with a particular set of keys. I'm not sure what all of the values are, but they include "Title", "Action" (which seems to be where you'd specify that this is a named destination, though I don't know what that value would be), and "URI" (which is used if this is an external link -- I suspect that this would specify the name of the named destination that you're linking to). Again, the specifics are hard to find.
Then iterate over the pages of the reader, importing each page to the PdfCopy. this page may help you.
Sorry I'm not more helpful to you. Good luck.
P.S. If anybody else knows of a better tool that's either (L)GPL or BSD licensed, I'd love to hear about it.