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K2pdfopt News Archive
K2pdfopt optimizes PDF/DJVU files for mobile e-readers (e.g. the Kindle) and smartphones. It works well on multi-column PDF/DJVU files. K2pdfopt is freeware.
Last updated Nov 2, 2012
 

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K2PDFOPT NEWS
26 Dec 2023    K2pdfopt v2.55 released. This version is compiled on the latest OS's with the latest C compilers and the latest third-party libraries. There is one bug fix (bookmarks work again). See details in the k2pdfopt version history. I've posted an updated performance benchmark on my blog page.
1 Apr 2023    I guess the Mac download using the Safari web browser has not been working for a while. I think I have fixed this. If you cannot download using Safari, try using a different web browser--e.g. Firefox or Chrome. Also, to run the Mac binary, be sure to watch my help video.
18 Feb 2023    I've added to my blog some benchmarking / testing that I did when I was building k2pdfopt v2.54: a gcc v12 / k2pdfopt benchmark and an updated tesseract accuracy study.
18 Feb 2023    The download page for some time was not correctly showing a link to the Win64 v2.54 version. I'm not sure what caused it. It has been fixed.
6 Jan 2023    K2pdfopt v2.54 released. There is no update to the k2pdfopt source code in this release--only to the libraries--notably Tesseract v5.3.0 which improves the OCR speed. This version is also compiled with the latest gcc compiler, v12.2. See details in the k2pdfopt version history.
6 Mar 2022    I did some experimenting with Tesseract (OCR) v5.1 today. I compiled it and benchmarked it with a standard test I have. It uses the same training files and has identical accuracy to Tesseract v4.1, but uses a new 32-bit floating point calculation technique, that, interestingly, is 30% faster on the "best" english training file but 40% slower than Tesseract 4.1 on the "fast" english training file (on a Core i9-9900 CPU). The optimum character height of a capital letter is between 25 and 35 pixels for the best accuracy for both Tesseract v4.1 and v5.1.
4 Mar 2022    I've added a Linux Aarch64 binary to my download page which I cross-compiled on a Debian 10 virtual linux box on my Windows PC. I'd be curious if anybody can give me feedback whether it works or not. I had a user request a binary for their Pinephone, so I'm hoping this will work.
12 Jul 2021    I've re-worked my download page a bit to try and make it smarter about forcing a fresh load every time as opposed to the browser pulling it up from an internal cache, which can cause problems with expired capcha values. If you get an expired capcha, try refreshing the download page manually in your browser (click the refresh button).
23 Jan 2021    Apple OS/X M1 Arm-64 version of k2pdfopt v2.53 released. See the download page. This version will only run on the latest Macs with the M1 chip, which is a very impressive performer. See my blog entry on it.
18 Jul 2020    K2pdfopt v2.53 released. This version improves OCR multithreading, adds better DJVU support (text layer extraction), adds CBZ support, and is compiled with the latest third party libraries, e.g. Tesseract 4.1.1. See details in the k2pdfopt version history.
12 Jun 2020    K2pdfopt v2.52 released. This is primarily a bug-fix release, fixing over 20 issues that have accumulated over time. There are also a few enhancements including the ability to directly download Tesseract OCR language data files (finally). See details in the k2pdfopt version history.
9 May 2020    A new Mac OSX and Linux GUI called rebook is being developed for k2pdfopt by Pu Wang. It is written in Python and Tcl/Tk. Wang's goal is to mimic the Windows GUI as closely as possible. While adding rebook to my third-party contribution page, I took the time to update that page, particularly the section on KOReader, which I had not looked it in a while. It has evolved into a very polished application for e-ink devices.
14 Mar 2020    I'm still here. The amount of time I can afford to work on k2pdfopt has dwindled, but I still hope to get around to some key bug fixes and updated builds at some point. In the mean time, I do still answer questions on the mobileread forum and I just did a long overdue update to the OCR help page.
3 Aug 2019    My site (willus.com) now offers SSL/https connectivity. Apparently this happened without my being notified, at no charge to me, which is nice. As a result, today I configured my site (and my backup site willus.org) to automatically re-direct http requests to https requests. Enjoy the added security!
5 Jan 2019    K2pdfopt v2.51a for MS Windows released. Fixes a bug displaying PDF file information in the MS Windows GUI. The download page now shows v2.51a. The MS Windows binaries will show v2.51a, but the Linux and OSX binaries will show v2.51 since they are not affected by the bug. See details in the k2pdfopt version history.
4 Jan 2019    K2pdfopt v2.51 released. This fixes an issue in v2.50 where the Tesseract OCR would not run on modern PCs and enhances the accuracy of the Tesseract v4.0.0 OCR. See details in the k2pdfopt version history.
31 Dec 2018    I've posted some k2pdfopt beta Windows builds (link since removed) due to reports of v2.50 Tesseract OCR failing on machines with AVX-capable CPUs (which includes most modern CPUs since Sandybridge). If some people could give me feedback on whether the beta version Tesseract OCR works on their AVX-capable CPU, that would be helpful. If you have time, please try all three versions.
27 Dec 2018    K2pdfopt v2.50 released. The major enhancement in this release is compiling in the Tesseract v4.0.0 library. Most other third-party libraries have also been updated to recent releases. See details in the k2pdfopt version history.
15 Oct 2017    Added a new video to the Mac OSX help page demonstrating how to download and run k2pdfopt in OSX Sierra.
20 May 2017    K2pdfopt v2.42 released. This revision adds bitmap file output (see -o option), dewarping (like ScanTailor, see -dw option), better auto-cropping (-ac option), and Kobo Aura One device dimensions. See details in the k2pdfopt version history.
25 Feb 2017    K2pdfopt v2.41 released. This is mostly a library update, with one minor new feature (erosion filter to thicken text). See details in the k2pdfopt version history.
1 Jan 2017    K2pdfopt v2.40 released. Tesseract OCR processing is now multi-threaded and so runs significantly faster on modern, multi-threaded CPUs like Intel's Core-i7. See details in the k2pdfopt version history.
26 Nov 2016    K2pdfopt v2.36 released. This is a mostly bug-fix release with some minor new features. See details in the k2pdfopt version history.
29 Oct 2016    Added SHA-256 hash code links to the download page. You can hover over the buttons or click the "sha-256" links below them.
22 Oct 2016    K2pdfopt v2.35 released. This is a mostly bug-fix release with some minor new features and updated libraries and compiling platforms. See details in the k2pdfopt version history.
10 Oct 2016    For now, if you want to run k2pdfopt in Mac OSX Sierra, you'll need versions that are not compressed with UPX, which is broken in Sierra. (22 Oct 2016 -- You can now get v2.35 which works in Sierra.)
21 Mar 2016    K2pdfopt v2.34b released. This release fixes two more MS Windows bugs. The Linux and Mac versions are not affected (still v2.34a).
20 Mar 2016    Updated mupdf_mod/string.c in the v2.34 source archive. It was not the correct version.
19 Mar 2016    K2pdfopt v2.34a released. This release fixes a couple more bugs, including a critical GUI issue which did not allow editing of the "Additional Options" entry.
18 Mar 2016    K2pdfopt v2.34 released. This release adds some feature requests and bug fixes from the past few months, including the ability to select the font size of the converted document and the selection of an output folder in the MS Windows GUI. See all of the other new features, improvements and bug fixes in the k2pdfopt version history.
3 Oct 2015    K2pdfopt v2.33a released. This release fixes a bug in the MS Windows GUI--the preview page selection control went missing in v2.33. So much for my GUI regression testing.
27 Sep 2015    K2pdfopt v2.33 released. This release adds some feature requests and bug fixes from the past few months. In the MS Windows GUI, I've added the ability to select multiple crop boxes. See all of the other new features, improvements and numerous bug fixes in the k2pdfopt version history.
6 Mar 2015    K2pdfopt v2.32 released. This release adds a feature I've long wanted to implement in the MS Windows GUI--graphical selection of the crop margins. See all of the other new features, improvements and numerous bug fixes in the k2pdfopt version history.
23 Jan 2015    K2pdfopt was used by the JSTOR folks as part of their participation in the NYPL Open E-book Hackathon.
27 Dec 2014    K2pdfopt v2.31 released. This release adds minor new features and context sensitive help in the MS Windows GUI. It is compiled with MuPDF v1.6 and also includes source code modifications for better compatibility with KOReader. See the details in k2pdfopt version history.
26 Nov 2014    K2pdfopt v2.30 released. Now with wide character support (UTF-16) in Windows for file names (e.g. should work with file names that have Chinese or other non-8-bit characters). Details and other updates are listed in the k2pdfopt version history.
25 Jul 2014    K2pdfopt v2.21 released. Now compiled with MuPDF v1.5. See the details in k2pdfopt version history. For people using the source code, there is no change to any of my source code between MuPDF v1.4 and v1.5. The same source compiles with either version.
25 Jul 2014    K2pdfopt v2.20 released. This revision has several new features and bug fixes. See the details in k2pdfopt version history. Since v2.20 has a significant number of changes, I will keep the v2.18 download option available.
14 Jun 2014    I added a screen shot of k2pdfopt running in Wine on Linux to my third-party contributions page.
14 Jun 2014    K2pdfopt v2.18 released. This is a minor bug fix. See the details in k2pdfopt version history.
2 Jun 2014    K2pdfopt v2.17a released. This is a MS Windows-only bug fix. In v2.17, the support for MS Windows system fonts does not work correctly in MuPDF. This is fixed in v2.17a. See the details in k2pdfopt version history.
17 May 2014    K2pdfopt v2.17 released. This is a library update release. The MuPDF, Turbo JPEG, PNG, and FreeType libraries have all been updated to the latest releases. See the details in k2pdfopt version history.
3 May 2014    K2pdfopt v2.16 released. This is a bug fix release. See the details in k2pdfopt version history.
30 Mar 2014    I've added a new PDF Conversion Tips page to my web site, and also updated my examples below.
22 Mar 2014    K2pdfopt v2.15 released. This is a bug fix version which primarily fixes some memory leaks. See the details in k2pdfopt version history.
31 Dec 2013    K2pdfopt v2.14 released. This is a mostly cosmetic change to some of the source files, but it does fix an incorrect Win32 build from v2.13. Thanks to Dirk Thierbach for some of the source modifications. See the details in k2pdfopt version history.
30 Dec 2013    K2pdfopt v2.13 released. The crop box option (-cbox) is more powerful now, KOReader patches have been applied, and other minor bug fixes and enhancements have been incorporated. See the details in k2pdfopt version history.
21 Dec 2013    I have modified my download script so that it should correctly implement HTTP_RANGE byte ranges to support re-startable downloads. I don't know how to test this, though.
30 Nov 2013    K2pdfopt v2.12 released. Another minor bug fix for the Windows versions only. See the details in k2pdfopt version history.
30 Nov 2013    I revised some of the help pages today, adding more screen shots of the Windows GUI and a new video.
28 Nov 2013    K2pdfopt v2.11 released. This is a minor bug fix for the MS Windows GUI only. See the details in k2pdfopt version history.
23 Nov 2013    K2pdfopt v2.10 released. In v2.10, k2pdfopt now preserves the PDF bookmarks / outline tree. It also allows you to supply your own set of bookmarks. There is also a command-line crop-box option which gives k2pdfopt similar capability to Briss, for example--allowing the user to select arbitrary crop boxes from even and odd pages. Various bug fixes have also been implemented. See the full details in k2pdfopt version history.
21 Sep 2013    K2pdfopt v2.03 released. This update only affects the MS Windows binaries. The GUI correctly converts in native mode now and MuPDF has been modified with patches from Sumatra PDF reader so that it now utilizes MS Windows system fonts for non-embedded PDF fonts. See the full details in k2pdfopt version history.
16 Sep 2013    K2pdfopt v2.02 released. This fixes most reported issues to date, including the hyphen detection. It also implements a faster bitmap re-sampling function for 32-bit versions. See the full details in k2pdfopt version history.
4 Sep 2013    K2pdfopt v2.01 released. This fixes a significant memory leak which was causing k2pdfopt to crash or slow down when converting large PDF files. It also fixes some issues with the preview in the MS Windows GUI. See the full details in k2pdfopt version history.
2 Sep 2013    K2pdfopt v2.00 released. This is a major new release which now includes a GUI for MS Windows (don't worry, command-line fans--k2pdfopt is still fully useable from the command line in MS Windows). Here is a GUI screen shot. This version also significantly improves conversion of re-flowed native-PDF documents by extracting the text from them without requiring OCR. See the full details in k2pdfopt version history.
14 Aug 2013    Ashley DaSilva has contributed a python GUI for k2pdfopt, Journal2eBook, which runs under all platforms supported by k2pdfopt.
23 Jul 2013    K2pdfopt v1.66 released. This is a bug fix / maintenance release that fixes the most commonly reported issues from v1.65 except for the unicode file name issue (with Chinese characters in the file name, for example--k2pdfopt uses 8-bit ASCII for internal file names). See details in k2pdfopt version history.
8 Jul 2013    Jens Wallauer has updated his Windows GUI to v2.0.2.0, now with support for multi-threaded conversions.
28 Jun 2013    Fiore Basile has contributed another basic Mac OSX GUI, MacReFlower, tuned for the kindle paperwhite.
15 Jun 2013    Jens Wallauer has udpated his Windows k2pdfopt GUI to version 2.0 with more on-line functionality and more customizeability.
11 Apr 2013    Jens Wallauer continues to update his Windows k2pdfopt GUI, which now supports Tesseract OCR with version 1.04.
6 Apr 2013    K2pdfopt v1.65 released. This is a bug fix / maintenance release with some minor new features. See details in k2pdfopt version history.
12 Jan 2013    Adrian Zandberg's reFlower GUI for k2pdfopt now includes a Windows version. See my k2pdfopt contributions page.
5 Jan 2013    K2pdfopt v1.64a released. This version fixes a native PDF output bug in v1.64. See details in k2pdfopt version history.
4 Jan 2013    K2pdfopt v1.64 released. This version improves the native PDF output so that contents from multiple source pages can reliably be displayed on one output page. It also has some other minor new features and a memory-leak bug fix. See all the v1.64 changes in the k2pdfopt version history.
3 Jan 2013    An OSX GUI for k2pdfopt, reFlower, has been contributed. See my k2pdfopt contributions page. Thanks to Adrian Zandberg.
20 Dec 2012    K2pdfopt v1.63 released. The most notable new feature is Unicode-16 copy/paste support for more languages when using the Tesseract OCR engine. See my OCR help page. See all the v1.63 changes in the k2pdfopt version history.
15 Nov 2012    K2pdfopt v1.62 released. This release is mostly for the KindlePDFViewer team (mobileread.com forum) in that I have significantly re-organized the source code to be easier to integrate with their application. The bulk of the k2pdfopt-specific source code now resides in a k2pdfopt library, and I have eliminated all global variables. There are some minor new features and bug fixes. See the full details in the k2pdfopt version history.
6 Nov 2012    The k2pdfopt help videos now play correctly on iPads and iPhones.
5 Nov 2012    I've updated the Windows v1.61 binaries to patch a problem I had in my compile of the Tesseract library for Windows which was causing the Windows binaries to crash on some systems. If you downloaded v1.61 Windows binaries before today, re-download them. The updated Windows binaries will identify themselves as v1.61a.
4 Nov 2012    I've created a couple of k2pdfopt videos that demonstrate how to use it: an overview video and a video about the native PDF output modes.
3 Nov 2012    K2pdfopt v1.61 released. This fixes a v1.60 bug where some user menu inputs were not getting applied to the conversion, and it also is compiled with Tesseract 3.02.02 and Leptonica 1.69. See the k2pdfopt version history for details.
1 Nov 2012    K2pdfopt v1.60 released. The most significant new feature is native PDF output, which, if used judiciously on the right types of files, can result in much smaller output files with selectable/searchable text and no loss of fidelity. This is done by rendering each page exactly as it is rendered in the source file, but with translation, scaling, and cropping directives (much like soPdf and Cut2Col--k2pdfopt even has a -mode sopdf option which mimics soPdf output). Native PDF output is enabled by default if text wrapping/re-flow is disabled (it is not compatible with text wrapping). There are several other useful new features in v1.60 (including the ability to mimic my pdfr program--use -mode copy), as well as the usual host of bug fixes. I have maintained a download link for v1.51 in case users have trouble with the new version.
21 Sep 2012    K2pdfopt v1.51 released. This is a bug-fix/minor improvement release. There are some command-line options and interactive menu options which have changed, so please see the k2pdfopt version history for details.
19 Sep 2012    Jens Wallauer has updated his K2pdfopt Windows GUI, available on my k2pdfopt contributions page.
9 Sep 2012    There is now an ARM binary of k2pdfopt (no OCR) on the k2pdfopt download page which shoud run on most android devices, thanks to RefUser. I cannot offer any support for this version, but see the mobileread.com k2pdfopt forum thread if you have questions.
7 Sep 2012    K2pdfopt v1.50 released. The major new feature is optical character recognition (OCR--English only), which allows you to search or copy/paste the text of the PDF output file. There are also several other new features that various users have requested. I've also released the source code and officially copyrighted k2pdfopt via the GNU Public License, v3. Note that OCR is not enabled by default. See how to use it on my OCR help page. I have maintained a download link for v1.41 in case users have trouble with the new version.
31 Aug 2012    The download count on k2pdfopt has now topped 100,000, the bulk of that occurring in the last 13 months, ever since freewaregenius.com posted the first review.
5 Aug 2012    The first k2pdfopt GUI (Windows only), contributed by Jens Wallauer, is now available on my new k2pdfopt contributions page. This should be welcome news for Windows users who are uncomfortable using the command line.
11 Jun 2012    K2pdfopt v1.41 released. This is a bug-fix / minor improvement release.
5 Apr 2012    K2pdfopt v1.40 released. This update involved a lot of new code, so I bumped the version up from 1.35 from 1.40. The major new feature is true text wrapping / re-flow (on by default), and most of the improvements in this version will be noticeable primarily when wrapping text. The vertical spacing and indentation in the source document should be better mimicked now, and there is also an option for ignoring tiny marks (defects) on scanned documents. Because the text wrapping was completely re-written for v1.40, I am leaving up the v1.35 downloads for those rare cases where people might prefer the way v1.35 breaks lines.
16 Feb 2012    K2pdfopt v1.35 released. This version includes smarter column flow and a debugging option to show how k2pdfopt is interpreting your file.
30 Dec 2011    K2pdfopt v1.34a released. After a hiccup with v1.34 not working in Windows and Linux due to build issues, hopefully 1.34a has this resolved. It is mostly a maintenance release, and includes some minor bug fixes and new features.
11 Nov 2011 K2pdfopt v1.33 released. It now auto-detects the orientation of the source document (assuming it is mostly text). That is, if the document is turned on its side, k2pdfopt will automatically rotate it before processing. There is also now an option for fully justified output (scroll to bottom of the help page for an example).
  29 Oct 2011 I have modified the download process to include a capcha because I am having instances of repetitive downloads from the same IP number (from bots?) that are eating my bandwidth.
25 Oct 2011 K2pdfopt v1.32 released and fixes a significant bug in v1.31, which introduced DJVU file reading capability.
28 Sep 2011 K2pdfopt v1.28 offers the first 64-bit Mac OSX version.
25 Sep 2011 K2pdfopt v1.27 changes the default conversion so that it only handles up to two columns maximum. Use the "co" option in the user menu (or -col command-line option) if you have a document with more than two columns.
10 Sep 2011 K2pdfopt v1.22 released and offers a Mac OSX version.
29 Aug 2011 K2pdfopt v1.16 released--a significant update. It has bug fixes, runs faster, creates significantly smaller, sharper PDF files, has a new landscape option, and supports right-to-left page scanning, but the most noticeable change is that it prompts you for conversion options by default. To continue with the default conversion process, just press <Enter> after dragging your PDF (or DJVU) icon to the k2pdfopt icon. To disable the prompting, see the k2pdfopt help page.
The complete list of k2pdfopt changes is in the k2pdfopt version history.

This page last modified
Friday, 02-Nov-2012 19:35:48 MDT