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Old 10-25-2010, 05:03 PM   #1
Qxr
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Is it possible to reduce display colour depth?

Some low-contrast scanned texts are hardly readable due to the relatively high colour depth supported by DR800. My question is to the reader software gurus: can it not be adjusted somehow for PDF's and DjVu's? Thanks!
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Old 10-26-2010, 01:05 PM   #2
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i'm afraid nobody from the old-IREX crew will read your problem and certainly not helping out. That's what happens when a company get busted. Unfortunately it is like it is. I'm still very glad to have the DR800SG and reading on it is a pleasure.

Hopefully some of the users can help you out.
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Old 10-26-2010, 02:28 PM   #3
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Originally Posted by Franky View Post
i'm afraid nobody from the old-IREX crew will read your problem and certainly not helping out. That's what happens when a company get busted.
That's not necessarily true. There are members of the IREX development team that are still reading/participating in this forum.

Regarding the original question, I assume by "color depth" you're referring to the shades of grey that the display is interpreting from the PDF? I don't think it's really a DR800 question, but rather whether or not there are any software applications that will let you darken a PDF document. I assume these are being scanned as images, and not OCR'd into text?
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Old 10-26-2010, 03:56 PM   #4
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Correct, I meant files without OCR. Thank you for your advice - I'm currently looking for such applications. Just wondered if the reader's software offered a way to reduce/restore the number of displayed colors (by running a script or something like this).
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Old 10-26-2010, 07:37 PM   #5
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Originally Posted by Qxr View Post
Correct, I meant files without OCR. Thank you for your advice - I'm currently looking for such applications. Just wondered if the reader's software offered a way to reduce/restore the number of displayed colors (by running a script or something like this).
Not that I know of.

Technically, I think a PDF full of images can probably be extracted out into individual JPG/GIF/etc files (whatever format it uses internally). You could then use whatever paintshop type program to darken them, and then recombine into a PDF again. There are probably tools that make all of that a lot easier though, but I'm not an expert on them (obviously).
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Old 02-04-2011, 05:48 PM   #6
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significantly enhanced contrast for djvu files

A nice improvement has been made to Pocketbook DJVU reader by review:
http://www.mobileread.com/forums/showthread.php?t=119874
Maybe, some of our glorious developers will be interested to make this improvement for Irex, too? Here is the direction from review: http://www.mobileread.com/forums/sho...0&postcount=19
Thanks for all you've done, guys!
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Old 02-04-2011, 06:29 PM   #7
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I think that the experts that have ported the djvu reader for the DR's are luite and also, more recently, yuri_b ...
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Old 02-06-2011, 03:46 AM   #8
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We are using FORMAT_GREY8 that gets 256 grey levels, that can be converted to 4 byte gray level.
What he suggest is convert image to white black 2 colors, and this IMHO not good, because I'd like see also images in books, not only text.

Sincerely
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Old 02-07-2011, 01:40 PM   #9
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Yura,
I see your point, but maybe it would be possible to make the djvu viewer suggesting gray-level options when a djvu file is opened? I saw a lot of texts that looked pale with the 256 greys, but might be more readable with 4 grey level on. What do you think?
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Old 02-07-2011, 01:51 PM   #10
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Irex E-Ink display is 4-bits grey, so what you see is 16 colors image. If we will convert it straightforward to 2 level black/white it not always will enhance image quality, better will be to use algorithm for enhancing contrast.
The problem: processor used in IREX ebook (and actually in every ebook) not designed for heavy image manipulation, it's too week. Better approach would be offline enhancement of djvu book using more advanced tools for it.

In sources of djvu plugin I see that luite tried to enhance image by converting it to 4-bits before display. This code in comments, maybe something not work as expected, or his algorithm too slow.

Sincerely
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Old 02-07-2011, 02:38 PM   #11
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Quote:
Originally Posted by Shaggy View Post
I assume these are being scanned as images, and not OCR'd into text?
Even so, when I tell my scanner that what it's scanning is text, it tries to interpret everything as black and white (no half-tones) and that really improves readability of such text, compared to scanning as photos (which yields plenty of gray scales and very little true black or true white).

In short: if at all possible, I'd try to solve this problem at the source, at the scanner.
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Old 02-07-2011, 05:01 PM   #12
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there is a rather detailed discussion of djvu in message #3 of this post

http://www.mobileread.com/forums/sho...te#post1154480

that might (or not) be relevant to this post here ...
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