Mailing-List: contact users-help@pdfbox.apache.org; run by ezmlm
Precedence: bulk
Reply-To: users@pdfbox.apache.org
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 9.0 \(3094\))
Subject: Re: Merging pages of two PDF documents
From: Maruan Sahyoun <sahyoun@fileaffairs.de>
In-Reply-To: <184B5EB5-BCE9-47AF-AFF3-5154002E06F1@gmx.de>
Date: Tue, 27 Oct 2015 06:51:18 +0100
Content-Transfer-Encoding: quoted-printable
Message-Id: <9BCB8DD8-8A24-4358-9469-97950B41D052@fileaffairs.de>
References: <184B5EB5-BCE9-47AF-AFF3-5154002E06F1@gmx.de>
To: users@pdfbox.apache.org

Hi,

> Am 26.10.2015 um 22:46 schrieb Timm Friedholz <timm.friedholz@gmx.de>:
>=20
> Hello,
>=20
> I have some PDF documents in which the glyph-Unicode character mapping =
is destroyed so that it's not possible to search and copy the text.  In =
an attempt to remove this restriction I've converted the PDFs to TIFF =
images and performed OCR on them using tesseract.  Tesseract exports the =
recognized text as PDF files in which the text is positioned =
transparently on top of the images such that the text is searchable and =
selectable.
>=20
> The problem is that the images in the PDF that tesseract outputs are =
gray-scaled, large and high contrast versions of the original PDFs and I =
would like to have the quality and file size of the original PDFs =
instead.  Thus my idea is to copy  the text objects of the OCR output to =
the original PDFs.  To avoid interference with the old text, I've =
converted the original PDFs to vector paths using Ghostscript:  gs -o =
out.pdf -dNoOutputFonts -sDEVICE=3Dpdfwrite in.pdf
>=20
> Now the problem is that I'm not sure how to approach this =
programmatically.  Can I simply iterate over the pages and copy the text =
objects from each page of one document to the corresponding page of the =
other document?  Which operators do I need to copy if I parse it token =
by token?  Should I actually do it as directly via the PDFStreamParser =
class or are there abstraction in PDFBox that will make this easier?

the easiest might be to
a) remove the images from the OCR'ed document
b) overlay the pages from the OCR'ed document over the original PDF =
using org.apache.pdfbox.multipdf.Overlay

BR
Maruan


>=20
> The code for the PDF export by tesseract is here:
>=20
> =
https://github.com/tesseract-ocr/tesseract/blob/dd8c12997385cf7f5961093bcd=
44f0396b08f96f/api/pdfrenderer.cpp#L1
>=20
> Here is the line that specifies the text objects:
>=20
> =
https://github.com/tesseract-ocr/tesseract/blob/dd8c12997385cf7f5961093bcd=
44f0396b08f96f/api/pdfrenderer.cpp#L317
>=20
> Thanks.
>=20
> Timm
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@pdfbox.apache.org
> For additional commands, e-mail: users-help@pdfbox.apache.org
>=20


---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@pdfbox.apache.org
For additional commands, e-mail: users-help@pdfbox.apache.org