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Old 07-12-2018, 06:39 AM   #1
retrography
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Reading scanned PDFs on Inkpad 3

I am in academia and I often have to read old documents that do not exist in digital format, and thus I have to digitize them myself using our copying machine (gives you PDFs with jbig2 + invisible text on top).

I have noticed that PocketBook's default e-reader (on Inkpad 3) is extremely finicky with jbig2 images (the best format for scanned text), and often fails on larger images, even when Ko-reader can handle the file.

Moreover, PocketBook seems to have great problems identifying text in the scanned files, whether the file uses a superposed image/text format or it uses the more advanced Acrobat ClearScan format. Actually, which file works and which one not seems to a completely random variable.

I wanted to know if anyone here has had success with a specific workflow for producing scanned PDFs appropriate for reading and annotation on PocketBook devices. For instance, whether a specific format, or a specific version of a software are more likely to produce compatible files.
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Old 08-27-2018, 07:09 PM   #2
rkomar
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I had good results in the past using PDFBeads to create PDF files from scanned images. It converts black and white images to jbig2 format within the PDF, and I hadn't noticed any problems with those on my Inkpad 1 (except for being slow to load). However, PDFBeads looks to be unmaintained now, so I'm not sure if it still builds on modern systems. I guess you can always just try it and see.

JBIG2 is the most efficient format for black and white images, but the CCIT Group 4 format is pretty good, as well, and decodes much more quickly on the PocketBook devices than JBIG2. Perhaps if you could store the images in that format in the PDF files, it would work better on the ereader. The PDF files would be larger, but I think that's a small price to pay for speed and reliability.
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Old 08-31-2018, 05:54 AM   #3
retrography
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Quote:
Originally Posted by rkomar View Post
I had good results in the past using PDFBeads to create PDF files from scanned images. It converts black and white images to jbig2 format within the PDF, and I hadn't noticed any problems with those on my Inkpad 1 (except for being slow to load). However, PDFBeads looks to be unmaintained now, so I'm not sure if it still builds on modern systems. I guess you can always just try it and see.



JBIG2 is the most efficient format for black and white images, but the CCIT Group 4 format is pretty good, as well, and decodes much more quickly on the PocketBook devices than JBIG2. Perhaps if you could store the images in that format in the PDF files, it would work better on the ereader. The PDF files would be larger, but I think that's a small price to pay for speed and reliability.


Only if I had the time to re-convert all my books for each new reader I buy! Well, if they announce that their reader reads PDFs, then it should read PDFs, jbig2 or not. It seems to me they don’t want to pay any software license whatsoever.
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