I am working on PDFs using Leaves. I'm unable to figure out how to make annotations. I haven't used Quartz 2D much and would like some direction
Adding write annotation support is hard.
Quartz 2D won't help you there.
You need to manually parse the PDF. (e.g. with NSScanner) and build up the XRef tree of all the PDF objects. Then you're writing a new trailer that replaces the /Page object and attaches all new annotation data. It's quite hard to get right, and the 2000 pages PDF reference is not very helpful on that. I worked the better part of the year for proper annotation support (Highlight, Underscore, Strikeout, Ink, Note, ...).
And when you want highlight annotations, you also want text selection (else the user would have to free-draw a highlight - not a nice experience.) Getting the correct frames for the text glyphs for all PDF font types is another level of horror; in PDF there's no notion of a word or a column. Just single glyphs. The rest is algorithms and guessing.
I even spoke with some Apple engineers how they did it [text selection, annotations], and they told me a three-person team worked about three years on their implementation.
Related
this is the first I'm working with PDFs on this level. So please be patient with
my noob question. I understand the logical and physical structure of an PDF file
on a basic level.
I have an PDF that contains a dummy ID that needs to be replaced. To check, if there
is way to do this, I used qpdf to expand the PDF using
qpdf --qdf --object-streams=disable orig.pdf expanded.pdf
Using a hex editor I located the dummy ID in expanded.pdf and changed the value by
simply swapping two digits
<001800180017> Tj => <001700170018> Tj
and saved it. Opening expanded.pdf in Acrobat didn't show the modification. The original
ID 443 is still rendered, but searching for "443" doesn't find it. When searching for
"334", the modified content, I get the rendered original ID 443 highlighted.
The PDF consist of text and vector graphic. When I insert additional digits (which obviously
invalidates the offsets in the xref), I get an error message regarding a missing font and
all digits are shown as dots but the vector graphic is still in place. This seems to indicate
that the ID is not part of the graphic.
What did I miss?
EDIT 1:
After mkl's comment, I did a deeper analysis of my PDF and found, that beside the obvious graphic content, all text was rendered by a series of m/l/c commands follwoed by a BT/ET section. Color for stroke and non-stroke was 0,0,0 for both in the BT/ET section.
Is this because of the used embedded non-standard font?
Are PDFs with embedded fonts usually done this way? A graphics part for the visual representation and a transparent (hidden) text part just to get searching and highlighting capabilities?
Looking back I wonder what I did to get the dots when I first modified the
content. I seems impossible and I can't reproduce it either.
Thanks
Tom
First off, the following is merely guesswork as you could not share the pdf in question. Educated guesswork but guesswork nonetheless.
You report that you changed the value by simply swapping two digits in the text drawing instruction argument and now can successfully search for the value with swapped digits but that Acrobat didn't show the modification.
Furthermore you observed that all text was rendered by a series of m/l/c commands followed by a BT/ET section.
The main situation in which one observes text being rendered as arbitrary vector graphics (a series of m/l/c commands), is in pdfs in which the producer didn't want text extraction to be possible and replaced text drawing instructions by arbitrary vector graphics instructions.
This apparently is not the case in your pdf as the text drawing instructions are not replaced but merely supplemented by the vector graphics ones.
Supposing that this construct is used for a reason and not by accident, I can only assume that the pdf producer was not willing or allowed to embed the font in question but wanted the specific font appearance to be displayed without having to count on the font being installed on the computer the pdf is viewed on.
Thus, the text appearance is drawn using arbitrary vector graphics instructions and the following text drawing instructions actually draw nothing but merely make the text searchable and extractable. This way there is no need to embed the apparent font face as font program. (Text drawing instructions can be made to draw nothing either by using a font with all blank glyphs or by using the text rendering mode "invisible".)
If this assumption turns out to be correct, your task to replace the dummy id requires not merely editing the arguments of the text drawing instructions but also replacing the arbitrary vector graphics instructions showing the dummy id appearance by other instructions showing the actual id.
If you happen to have the font in question and are willing and able to embed it, you can actually replace the arbitrary vector graphics instructions by text drawing instructions using the font. Otherwise be prepared to also draw the actual id as arbitrary vector graphics.
Does anybody know if there is a way to check whether a list of Adobe Acrobat .pdf files contain rotated text (any text not at 0 degrees)?
I thought this would be simple, but I'm struggling to find an answer.
I am using ABBYY Recognition Server to OCR thousands of files and the results are quite poor where the text is rotated. I need to get a list of files that have rotated text to allow me to perform some pre-processing on them.
I usually use iTextSharp for .pdf automation and modification but don't seem to be able to find anything for checking text rotation.
Thanks
You could achieve your goal by extracting all words from these PDFs and checking if any of the words is rotated.
I would recommend you to use a PDF library higher level abilities for the task. Docotic.Pdf library is a good choice (of course, I am one of the developers of the library).
Here is an articles that shows how to extract words from PDFs with extra info about their position etc.
Each extracted word comes in PdfTextData object. The PdfTextData contains IsTransformed property to check if word is rotated, scaled, and / or flipped. You can also analyze PdfTextData.TransformationMatrix for more information about the transformation.
I'm trying to use pdf content (mathematics) in my webpage. I basically want to convert the pdf to some vector image. Converting the pdf to swf does the job very well, but as flash isn't supported on every platform, I'm trying to find another solution.
I read about svg, but as those pdf's contain a lot of mathematics, the result of the converters I found is really ugly and incorrect.
I've also thought about retyping the latex, and displaying it using mathjax, in some way this is the best solution, but also very time consuming.
The only thing I want is to convert it to a nice vector image, I don't want to change the content, or anything else. Besides converting to swf or retyping it, is there any other solution ?
Edit:
this is svg output
and here original pdf
The only solution I could find is illustrator.
Just open the pdf, save as svg, and choose to embed all used glyphs.
Result is perfect:
https://dl.dropboxusercontent.com/u/58922976/Sol-10.1.svg
what about using flash + raster image in case of platform without flash, if flash mostly works for you?
Your PDF is a little difficult for reasons that are probably not apparent to you.
The core problem with it is that some of the graphics in the document are actually drawn using custom glyphs. You can see this if you copy and paste the text out of Acrobat. There are a variety of unusual characters in there that don't seem to serve any useful purpose. That's those squares at the bottom of your SVG with EEs and FFs in them.
However these characters are actually custom glyphs for things like the braces around the matrices at the bottom of the page. So they are both fairly important and also very specific to this document.
I tried ABCpdf .NET to convert your PDF to SVG. It worked fine apart from these custom glyphs at the bottom. The output was about 90KB. It looked very similar to your inkscape SVG output but just a bit smaller (the inkscape one is 160KB).
The only way to get rid of these non-Unicode glyphs is to vectorize the text. I did this using ABCpdf and the output looked fine in SVG. But... vectorized text is big and SVG isn't a particularly efficient medium. The output was about 1MB! Zipped it goes down to half that but it's still no-where near as efficient as the original PDF.
The problems I am seeing here are going to be universal whatever format you use. These custom characters are always going to be problematic whether you output to SVG, SWF, HTML canvas, VML or indeed any vector format.
So what would I suggest? Well the obvious vector format that is widely used on the web is... PDF!
I know it's not quite what you're looking for but I think this is the realistic solution given the constraints above. :-)
I am trying to make an iOS app which would extract plain text from a pdf file and display it in a UITextView. Its simply not a pdf reader to view a pdf file but i would later wish to perform certain operations on that text.
I have already googled a lot but still not able to get an exact solution.
i already tried using https://github.com/zachron/pdfiphone
but the files are using ARMV6 architecture which seems obsolete with xcode 4.5
And if anyone can suggest some exact and non-confusing code using Quartz-2d framework of iOS then it would be great.
Here is An Sample code to Extract text from PDF Hope this Might Help You.
https://github.com/zachron/pdfiphone
This is a library to get the text out of a PDF for the iPhone.
Another Demo is there Which uses OCR technology find the link below
https://github.com/nolanbrown/Tesseract-iPhone-Demo
Also Check this page of the Quartz 2D Programming Guide, it covers everything you need to open and parse a PDF file in iOS. Note that it is not a simple task, since there's no method to extract the full text in one line. You have to work with the data as an input stream, using a CGPDFScanner
Two Other Libraries
https://github.com/KurtCode/PDFKitten/
https://github.com/mobfarm/FastPdfKit
This question comes up all the time. It is VERY hard to extract text from PDF in general. The PDF specification is not designed with text extraction in mind. There are many libraries that try to do the job, essentially by reconstructing the text from the geometric placement of the individual glyphs. These libraries have varying degrees of success, but will all fail on certain PDF documents. In fact, some PDF documents have Glyphs but no way to associate the glyph with a character. For these documents it is simply not possible to extract text, short of using some kind of OCR approach.
PDF is designed as a read-only format that is portable in the sense that a PDF document will be rendered identically on any platform. That is what it is best at, and what it should be used for.
If text is to be edited, do not use PDF.
Here (Extracting text from pdf using objective-c), I found an answer to your question and it works. But not so fine as i need it :(
it can extract only ascii
it return me only one paragraph
Good luck.
I want to read an existing pdf & extract the text and graphics information. Within graphics, currently i just need the drawn lines. There are many vendor component for reading PDF text, but are there ones that can give graphics info too ? Though free/open-source is preferred, I'm ok to commercial ones too.
The requirement is:
For every page in PDF:
Reading text blocks
Getting to know the canvas co-ordinate of the text block (rectangle containing the block). Note, for text with higher font size, the rect size will change.
Lines - need collection of (x1,y1,x2,y2) for every line in a page in pdf
Thanks,
- Seeker
This is my field, though the question is a bit old. Hopefully this still helps.
You leave some room for assumptions, so here are mine:
you seek a script, rather than stand-alone software
your object is archival
you are running command-line scripts:
Use this command line script, detailed at: http://stefaanlippens.net/extract-images-from-pdf-documents
you are running server-side code using imagemagick or graphicsmagick functions:
Something like "convert -background white -flatten test1.pdf test1.jpg" (imagemagick) will render the whole PDF page into a jpeg. If you want to then crop it to the image(s), then it depends upon the context of the project to determine the best script(s) to do that.
A rather complex question. If you wish to provide more details about the project, then I can provide some more guidance. Best of luck.