Willus.com Home   |   Archive   |   About  

Willus.com's K2pdfopt
Back to Willus.com's Software Archive

6 Mar 2015

(Windows, Linux, OSX)

(GUIs; Native Kindle PDF Viewer)

(with videos)






Arch Linux


Linux Install

Mac Install
K2pdfopt optimizes PDF/DJVU files for mobile e-readers (e.g. the Kindle) and smartphones. It works well on multi-column PDF/DJVU files and can re-flow text even on scanned PDF files. It can also be used as a general PDF copying/cropping/re-sizing/OCR-ing manipulation tool. It can generate native or bitmapped PDF output, with an optional OCR layer. There are downloads for MS Windows, Mac OSX, and Linux. The MS Windows version has an integrated GUI. K2pdfopt is open source. Here's a quick example (click on the images below to get the PDF files):

(8.5 x 11 PDF or DJVU file)
   . . . INTO THIS.

(6-inch reader screen)
     . . . OR THIS.

(4-inch smartphone screen)

MS Windows integrated GUI front-end

Unsolicited comments from k2pdfopt users (refresh the page to change the comments):

         "I just wanted to thank you for the k2pdfopt, is the best converter in my opinion, [and] does the work perfectly. It has helped me a lot in my studies." -- September 14, 2014         

         "Thanks so much for your extremely useful software." -- May 2, 2012         

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.
[... more news]

K2pdfopt (Kindle 2 PDF Optimizer) is a stand-alone program which optimizes the format of PDF (or DJVU) files for viewing on small (e.g. 6-inch) mobile reader and smartphone screens such as the Kindle's. The output from k2pdfopt is a new (optimized) PDF file. K2pdfopt is meant for text-based files on a white background which may also have graphics or figures, and it works equally well on native and/or scanned or bitmapped PDF or DJVU files. It is fully automated and can batch-process PDF/DJVU files. K2pdfopt works by converting each page of the PDF/DJVU file to a bitmap and then scanning the bitmap for viewable areas (rectangular regions) and cutting and cropping these regions and assembling them into multiple smaller pages without excess margins so that the viewing region is maximized. Making use of this method, k2pdfopt can re-flow text lines, even on scanned documents (see the Winnie the Pooh example below). You can see another example of how k2pdfopt works on this help page.

As of v1.50, k2pdfopt will also embed OCR text into the PDF so that text can be searched and highlighted, and v1.60 can create output files with the native PDF instructions from the source file (if the source file is PDF). Any kind of PDF/DJVU file (best if it has a primarily white background) can be converted. K2pdfopt works especially well on two-column or multi-column PDF/DJVU files such as IEEE and other technical journal articles (see examples below--it auto-detects two-column regions on the page), but even single-column files will often be significantly improved and much easier to read (see examples). K2pdfopt has the advantage over other PDF converters in that it fully preserves the rendered PDF fonts and graphics from the original file, unlike programs that convert the PDF to an e-book format. Also, because k2pdfopt is completely independent of language or fonts, it will work equally well on documents in any language.

   No install is required and no extra files or packages are necessary to run k2pdfopt. Just drag and drop your PDF/DJVU file icon onto the k2pdfopt icon to convert it. You will be prompted for conversion options (as of v1.16). Press <Enter> to convert the file using the default settings. A new PDF file with _k2opt at the end of the name will be created. The output file is optimized for viewing on Kindles and other mobile readers with 6-inch screens (if the settings are not customized). Or drop a folder full of PDF/DJVU files onto the k2pdfopt icon to batch process. You can even drop a folder full of bitmap images to have them converted into a single PDF as if they were pages of a PDF file.

See my k2pdfopt help page for more detailed help.

Note that if you have a Kindle 2, it must have the latest firmware that allows it to view native PDF files.

EXAMPLES (click on images to get PDF file)
Example Type Original
for Kindle

(default settings)
for Smartphone

(-odpi 250)
(must use -col 4)

(must use -col 4)
Scanned pages
Two-column #2:

    7-23-15    kindlefan.cn (In Chinese)
    7-10-15    blog.the-ebook-reader.com
    6-14-15    MacWorld.co.uk
    7-22-14    VidaSemPapel.com.br (In Portuguese)
    6-20-14    ghacks.net
    4-11-14    betanews.com
    4-11-14    TrishTech.com
    3-14-14    Dr. Simon Bance
    9-5-13    JonTedesco.net
    1-28-13    Intelligent Rumblings
    1-7-13    Net Buffalo (In Japanese)
    12-1-12    blog.trufanov.com (In Russian)
    11-4-12    abstractmodem.com (archived)
    9-20-12    ozgurlukicin.org (in Turkish)
    6-27-12    equiscentrico.com (in Spanish)
    6-26-12    ketabkhan.info (in Persian)
    1-4-12    TechLogon.com
    11-9-11    Świat Czytników (in Polish)
    11-5-11    tivasyk.info (in Ukrainian)
    11-1-11    WMLCloud.com
    10-31-11    linospapa.blogspot.com (in Greek)
    10-27-11    Steve Gibson's Security Now #324
    10-21-11    addictivetips.com
    10-12-11    Paper4Kindle (in Chinese)
    10-7-11    the-ebook.org forums (In Russian)
    (varies)    mobileread.com forums
    9-7-11    habrahabr.ru (in Russian)
    8-4-11    steepbend.ru (in Russian)
    8-3-11    ssnjara.wordpress.com (in Croatian)
    8-2-11    howtogeek.com (note comments from "willus")
    7-30-11    artiss.co.uk
    7-30-11    ideasfor.info (in Russian)
    7-27-11    guidingtech.com (note comments from "willus")
    7-22-11    blog.rgub.ru (in Russian)
    7-22-11    aldus2006.typepad.fr (in French)
    7-22-11    korben.info (in French)
    7-21-11    lifehacker.ru (in Russian)
    7-20-11    redferret.net
    7-19-11    freewaregenius.com (full review)

See my page on PDF Conversion Tips.

This is my plug for Krzysztof Kowalczyk's Sumatra PDF reader: a small, efficient, yet feature-rich open-source PDF reader that does everything I want. Sumatra also displays several file types other than PDF, including XPS, DJVU, CBZ, CBR, and PS/EPS (PS/EPS requires Ghostscript), EPUB, and MOBI. It is a refreshing alternative to Adobe's bloatware. I highly recommend it.

This page last modified
Friday, 07-Aug-2015 10:02:49 MDT