I have a PDF file, containing layers.
For example, on some pages, there are graphs, with additional data displayed on top of that graph, when clicking (layers).
Now I need to try to fetch all these layers out of the PDF file, or to be precise, I need ALL the data from that PDF file, including layers. The pdf file contains javascript to show/hide the layers when appropriate.
What is the best approach? Is there any tool that actually works for my intentions? Or should I write something myself? (If this is possible ofcourse).
Edit:
Here you can download the PDF file:
http://www.2shared.com/document/IutUfDfr/OR_erasmus.html
The password for viewing is: erasmus
I do not know if there are any tools per se but if you cannot find those you might do the following:
for each combination of on/off layers that you are interested in walk all pages and collect the content streams. Tokenize those and cut out the content you do not want to see (the commands you need to monitor to determine this are BDC and EMC). Save the stream again with the clipped content (naturally save the result in different files). You need something to read the PDF object structure and update some objects (there are lot's of libraries for that), plus you need tobe able to parse the content streams.
Now you will have a set of PDF files without layers (optional content) for which there are plenty tools to render to HTML etc.
Note: optional content <--> layer switches in the PDF viewer usually are 1:1 but the standard supports a full n:m mapping. I would concentrate on the real optional content blocks that can be turned on/off to keep things simple.
you can use this tool to extract images and text from even locked pdfs
http://download.cnet.com/Able2Extract/3000-2079_4-10249654.html
I use it myself sometimes and it has the ability to convert to HTML
Related
I am looking for a rough overview of how one would go about embedding graphics (coming from a PDF file) into another PDF file when writing a C++ document processor.
Background: I work on the LilyPond music typesetter, and recently added Cairo output to the system. Now I would like to support adding externally provided graphics to the PDF files that we generate (eg. adding a logo onto page laid out). This is trivial with EPS for PS output.
I can see how you could hook up Poppler to read the PDF, and render the PDF contents onto a Cairo surface, but I wonder if there is a simpler shortcut (eg. embed the PDF file as a binary stream, and then point directly to that stream).
If you need to go via an external route, like reading the PDF and writing it into an existing PDF using Cairo, that would be simpler. To do it manually:
A PDF page consists of a stream of operators for drawing it, and a dictionary of external resources (fonts, images etc.). To stamp one PDF page onto another, you would need to:
a) Find all objects for external resources in the stamp which are needed, and add them to the destination PDF.
b) Convert the page to a "Form Xobject", which is a sort of reusable piece of content. Add this to the /XObjects entry in the destination page, making sure to pick a fresh name.
c) Add some operators to the page content in the destination page to invoke the new xobject
To see how this might work, you could play with -stamp-as-xobject and -postpend-content "/XObjName Do" from section 8.4 of the cpdf manual.
Making this work for arbitrary PDFs is really not for the faint of heart, I'm afraid.
I know about Doc.SetOCGOrder() and the likes, but apparently the Acrobat API does not provide means to remove layers (aka optional content groups, ocgs), only to hide them from users while leaving them accessible via scripting.
I'm not forced to use Acrobat, in fact I'd prefer a FOSS-solution (or at least freeware) using e.g. pypdf2 or pdftk. edit There is another post using abcpdf, which is unfortunately not free. Is there any way to port that behaviour to Acrobat's JS or pypdf2? Essentially the answer seems to loop through every page's content, which seems to include the layers.
(Concerning merging, I notice pdftk does remove layers when merging multiple files, so one can simple pdftk A=input.pdf B=input.pdf cat A1-end output output.pdf.)
My approach so far: For the relevant layers obtained via GetOCGs() set locked=true and both initState=false and state=false. Then use SetOCGOrder() to remove the layer from the layers view. Unfortunately this is not perfect, since at least in Acrobat DC I can still select "show all layers" in the layers panel, which still shows the layer. One could merge all layers now, but neither did I find an option to achieve that programmatically nor do I believe that would actually remove the hidden layer's elements.
You can't do it programmatically but you can create an Action that will process a folder full of PDF files using Adobe Acrobat. Set the Action to use the PDF Optimizer to discard hidden layers and flatten visible ones. See the graphic.
I'm using pdftotext to extract info from a pdf. Currently using the -raw option. I do have a few problems with the PDFs I'm working with. If I select the text from top to bottom it selects in the following fashion.
PDF content:
A
B
C
It selects A then C and then B. So when I extract the text it is presented in the same way. Is there a way to reformat the PDF so I can select the content from top to bottom?
NOTE: I'm aware that if I omit the "raw" option the layout will be preserved, but it seems to be buggy when the document includes tables so raw works better for me.
Yes, you can reformat the PDF so that the content is returned from top to bottom. This is not something that can be easily done using Adobe Acrobat or any other viewer that I am aware of and here is why.
From the documentation of pdftotext, the -raw option is defined as
Keep the text in content stream order. This is a hack which often "undoes" column formatting, etc. Use of raw mode is no longer recommended.
"content stream order" is the important piece in the description.
In PDFs, the content on the page does not have to be written in the content stream (the instructions that are interpreted to display the page) in the order that a human would read the content when the page is rendered. The internals of PDFs do not care about the ordering, they were designed to reproduce the same visualization of a document on a variety of platforms. Since all that matters to PDF is the visualization, applications or libraries that write PDF tend to not order the content stream in any meaningful way.
So you can reorder the instructions in a content stream so that they are in the order a human would read them, it is not an easy task to do by hand and using a library that understands PDF to manipulate the content stream would be one way of doing this. Another way is to look for a more advanced tool to use to extract text from the PDF (there are a number of tools that will look at the placement of the content on a page rather than just where it appears in the content stream).
I am not aware of anything that will reorder the content stream in the PDF based on where the content appears on the page automatically though.
My client wants us to build a custom document viewer for their app. (It really, truly needs to be custom, because there are a ton of application-specific features they need.)
We built one for them last year that took PDFs, generated page images, and backed the images using a hidden layer of text that could be selected and copied. We did it in Flex. It was a nightmare. PDF is horrid.
This year, we need to build one in HTML 5 with similar requirements, except that most of the documents now are in Word or HTML, that is, they have reflowable text, instead of the fixed layout and glyphs of PDF. But they still want to do PDF in the same viewer.
I'm thinking that we need to convert all documents to some common file format that can handle both reflowable text and also the fixed-position glyphs of PDF. (Each document would probably support one or the other, but not both). It would be nice if it were an XML-like markup language that would say:
<text>here's some text</text>
-- or --
<glyph letter="a" name="my_a_glyph" position="10,10"/>
<image src="my_image" position="20,20"/>
or something like that.
Is there any existing file format out there that can handle it? EPUB won't do the fixed-position text, and PDF sucks in too many ways to describe.
I think you can look at FB2 (FictionBook 2) format . That is an XML-based format, designed for publishing books. It includes images, though I am not sure if they can be aligned absolutely.
Also, you can simply go with HTML and do HTML-to-PDF rendering when needed (there exists various components and libraries for this). I don't see (or you have not listed) any reasons why this way doesn't work.
GROFF? Maybe build a macro library to customize it, as needed.
Groff/troff/nroff, the "run off" programs of Unix, can output to postscript or HTML. The jump from postscript to PDF is built in to some PDF viewers; there are also several existing programs for it, pstopdf, for example.
GROFF has some fixed layout options and some flow-like options. With GROFF, it's almost easier to base most of the printout on flowing text, within proscribed bounds.
I need to programmatically embed an existing PDF (a small graphic) onto a specfic page on an existing PDF. Using iTextSharp I've been able to add a new page containing this embedded PDF, but what need is to modify an existing page by adding this graphic. Is this possible using iTextSharp or any other PDF-generation libarary?
I tend to do this sort of thing using Context, which is a Tex-based layout tool that in integrated into the pdftex Tex/Metapost engine. There's a learning curve involved, and installing Context isn't entirely trivial, but it makes very general programmatic document processing involving PDFs easy once you get the hang of it.
For this problem, you'd define two overlays, with the first overlay being the main PDF that you set to a background, and then on the page you want to change, defining a foreground overlay with a \setlayer command, which contains a single \framed box, which superimposes the second PDF using a \externalfigure command.
The nice thing about Context for this kind of task is that it works with PDF as its internal representation all the way through, so there is no unexpected blow up in file size or deterioration in image quality, which you can get with other tools that convert between formats.