In my opinion the relative inaccessibility of DjVu's libdjvu, including having their own bytestream compression contributed to the low acceptance of the DjVu format over the years and not patent issues. This hinders other software developers adapting their software to support DjVu and even more so
when porting to a new platform.
The DjVuLibre software has ...
DjVu files are normally image only. From these file sections can be selected as images but not as text¹.
If OCR was applied during, or after, the conversion to DjVu. Extra information is stored in the files that associate image areas with text. Only if that was done you can select text from such a file².
Applying OCR to a DjVu file can be done online. If ...
There is no out of the box possibility.
The easiest way would be to convert the file to pdf, of course this would make the DjVu advantages disappear.
The alternative is to modify your Kindle by installing a compatible reader. One possibility that is still actively developed is Librerator (which is also a superior for viewing larger pdfs). You will however ...
The short answer is: PDF is not a good format for storing image data. The only reason that it is often used for doing so, is that it is one of the few formats (the other more well known ones are DjVu and TIFF), that allow you to store multiple (scanned) images in a single file.
The longer answer is that the possible storage of image data in PDF files is ...
PNG and DjVu are complementary formats as PNG is lossless and DjVu is lossy. DjVu's effectiveness in storing information is the result of using high quality compression and splitting a single image into multiple layers which essentially employ different compression algorithms.
As you indicate, you already know how to convert JPEG or PPM to DjVu, so the ...
As all pages are having the same or very similar width and height, this seems a "simple" problem of some pages having the wrong resolution. Most pages have metadata that specifies 600 DPI others only 96 DPI. That later are then of course displayed much larger.
My Linux distribution comes with djvutoxml and the corresponding djvuxmlparser (from package ...
You can read about the djvu file format here (with focus on the compression here), but the main difference is how the two formats compress the data.
Here are some relevant excerpts from Wikipedia:
DjVu has been promoted as an alternative to PDF, promising smaller
files than PDF for most scanned documents. The main difference
between DjVu and PDF ...
I have worked extensively with DjVu (and wrote the text extraction extension Calibre). I consider DjVu the better alternative for scanned multi-page documents, especially for efficiency reasons. Compared to the JPEG encoded pages you get in PDF or TIFF files you often have a 20x smaller file size.
For non-professional users this size difference often is not ...
The easier solution for this issue is to change the single quotes with double quotes. The have a different function under the DOS/Windows command prompt than under the common Linux shells.
djvused aaa.djvu -e "select 10; save-page-with b.djvu"
You can easily test the different workings of the single and double quotes by doing:
python -c "import sys; ...
There is AFAIK not such a utility that does exactly what you want but you can explode the file by repeatedly using the djvused utility:
djvused file.djvu -e "select <nr>; save-page-with <filename>"
where <nr> is the pagenumber and <filename> the output filename. I have a python utility that does this automatically for all the pages ...
What I always do to read DjVu ebooks on my Kindle is the following (In case they do not contain important images).
I convert them to plain text using: https://www.djvu-pdf.com/ - just choose the convert to plain text option after uploading your file
I open the text file with my Kindle.
Like that you have the freedom to adapt font size etc.
There is a program called jPdftweak which will let you scale pdf pages to whatever size you would want. You can set the parameters for the conversion to the larger page size and jPdftweak will scale all the pages in the file in accordance with the settings you have made. jPdftweak is a cross-platform, free Java program.
First, use the djvutoxml tool to extract a text layer in XML format from the DjVu document.
At the command prompt, type:
path\djvutoxml.exe path\book.djvu path\book.xml
Instead path parameter substitute your location on the disk.
Then, using the regular expressions, remove the selected characters(placed between sharp brackets > <). ...
First, create your desired structure in a text editor.
On the first line will be placed keyword bookmarks in round brackets as a root.
Behind the chapter titles are located page numbers or page names (with a suffix .djvu). Before the number must be symbol sharp #. All parameters are enclosed in quotation marks "".
Lower order chapters are created by ...
I've been converting PDF to other formats for over 3 years. I've converted at least 20 books.
A PDF file is not easily convertible, except for text paragraphs. I have a lot of experience extracting text from PDF. PDF is an endpoint, not meant for further processing or extracting of text. You will find you have a LOT of problems extracting images and tables....
Well in my opinion and also testing knowledge of ereaders... the djvu and pdf doesn't hold that great difference anymore...
In the past djvu use to have a higher compression ratio cause the files to be much smaller in storage and also had higher quality rates at this compression...
Now with tech as far as now pdf is also able to have high compression ratio......
In 2018 is no better format for eBooks with a complex text layout (magazines, encyclopedias). For pure text and minimal images is there epub format.
I personally do not like PDF format. Badly working with this format.
There are not (good open source) tools to work with a PDF format, for example in Python.
Unfortunately, PDF is spread among ordinary people.
Good compression is only one of the advantages of the DjVu format, cf. e.g. my presentation.
I think however that we need better tools to handle the format conveniently. Some useful work has been already done by Jakub Wilk, cf. http://jwilk.net/software, but it is not yet enough.
If your ebook reader supports EPUB you might be better of extracting the images from the PDF and DjVu files and creating EPUB files from the resized images.
This of course depends on the handling of larger-then-screen images on your reader, if that is different for EPUB than for images embedded in PDF, then of course you should target the better supported ...
There is a Wikipedia help page on that subject. Apart from DjVuLibre you will need ImageMagick
Step 1: Convert PNG to PBM using ImageMagick's convert utility:
convert myfile.png tempfile.pbm
Step 2: Convert PBM to DJVU using DjVuLibre's cjb2 utility:
cjb2 -clean tempfile.pbm myfile.djvu
I achieved it with using DjVuLibre
If you install the djvulibre-bin (Ubuntu install link) package, you will now have the djvups command, which converts a DejaVu file to PostScript .ps. You can then use any tool (like ps2pdf) to turn that .ps into a .pdf.
Full command sequence
djvups original_file.djvu temp.ps
ps2pdf temp.ps outputfile.pdf
In my ...
You can use Duokan. It is available for Kindle 2, 3, 4, 5 and DX versions.
It's upgrade and it's safe.
The extension allows Kindle to work with EPUB, CHM, DOC, TXT, ZIP, RAR, JPG, PNG, BMP and DJVU formats.
Supports fonts in ttf format.
Allows smart display PDF pages: Classic view | Smart view
Kindle 4 contactless |
Kindle 4 ...
As for patents, it seems they should expire soon.
As for tools, the compression ratio depends havily on the quality of foreground/background separation. My experience confirms that the commercial software is usually better in this respect.
I should note however that Jakub Wilk's didjvu allows to select one of several foreground/background separation ...