Thread: Bug report
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Old 01-17-2011, 02:24 PM   #134
review got an A in got an A in got an A in got an A in got an A in got an A in got an A in got an A in got an A in got an A in got an A in P-Chem.
Posts: 315
Karma: 6448
Join Date: Nov 2010
Device: 903
Originally Posted by teofrast View Post

you mean that color scanned pdf as those from are not readable?
that is not a good thing to discover just after having ordered a pb902, as my library is mostly composed of this kind of files.
can someone confirm this and/or suggest a workaround?
Hello and welcome,
first things first: don't be frustrated. Many pdf files on archive have been enhanced to be of a very high quality and those files are excellent to read on the 903 or the 902. Especially the files which are prepared to be displayed on have been much better quality than they used to be.

However, my bug report comes from the fact the almost all other files on archive, which are scanned as colour images are barely readable on the 903. If you like I can take some pictures. Sure, it depends (as always) on the particular file but I have many which are barely readable.

I would recommend you will get the djvu files (if available of those files) instead of pdf. If you're not familiar with djvu I can go and explain this awesome file format briefly or you look up the wikipedia article. In one sentence: djvu files _can_ have separated layers (e.g. one for the background and one for the foreground and then there might be even an invisible text layer which is there so that you can search inside of scanned books (providing the invisible text layer has been created by OCR)). Further there is a mask which defines what is on one page background and what is foreground. The background is stored with high compression and the foreground with less loss of detail.

So in principle, if you've downloaded the djvu file instead of the pdf file you can simply choose to display the foreground or the mask. And this will give an excellent contrast. This is implemented in the djvulibre libaries as well as in many djvu file viewers. Just right click and select the layer you want to see.

The bad news: the djvu viewer of the pocketbook doesn't provide this option to the user. However, I've looked into the specifications and you can add annotations for the viewer which layer to display. Guess, what: the pocketbook 90x ignores these additional informations as well (I wrote a script to modify my djvu files to have this additional information and all djvu file viewers (apart from evince in linux) just obey these comments and just display the file b/w or the foreground (as chosen).

But not so the pocketbook.

Actually, I've went so far and looked up the source code of an older version of the djvu file viewer on pocketbook (http://pocketbook-free.sourceforge.n...urcecode.shtml). There in line 266 of main.c it says:

        mode = DDJVU_RENDER_COLOR;
now comparing this to
you can see that the other viewers provide options:

if (flag_mode == 'f')
  else if (flag_mode == 'b')
  else if (flag_mode == 'c')
  else if (flag_mode == 'k')
  else if (flag_mode == 's')
  else if (flag_format == 'r' || flag_format == '4')
of exactly the ones you want to chose. E.g. black and white, mask only or Foreground.

So you see it should be pretty straight forward to implement this change on the pocketbook but as long as pocketbook doesn't get the point that this is necessary we will never get an updated firmware. And there is a big discussion in this forum that they should release the SDK very soon so that the community can have a play with the software and fix the bugs (or add features) as they want.

Now, for me, I didn't want to wait until they publish the SDK. I just want to read with my ebook reader. But how am I supposed to do this if many files are barely readable.

To cut the long story short:
I've written a script which modifies all my djvu files in a very sophisticated way. It extracts all layers of the original djvu file (including the invisible text layer). Then it removes the colour layers and rebuilds the djvu file with the remaining layers. And you can't believe what a difference it makes on the reading experience.

I haven't published it yet as I haven't heard a feedback by others on the djvu reading experience. Especially when it comes to the files from However, if you and others are interested I'm more than willing to upload it.

This surely doesn't mean that this bug shouldn't be fixed in the firmware by pocketbook but at least there is an excellent workaround until they sort it out.
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