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Old 03-17-2017, 05:40 PM   #1
mike.foster
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k2pdfopt for yellow/brown pages

Hi,

I have a book whose pages are yellow/brown-ish (sample). It's for reading with an iPad. What command can I use with k2pdfopt to increase the contrast (no need to shrink)?
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Old 03-17-2017, 09:07 PM   #2
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Quote:
Originally Posted by mike.foster View Post
Hi,

I have a book whose pages are yellow/brown-ish (sample). It's for reading with an iPad. What command can I use with k2pdfopt to increase the contrast (no need to shrink)?
Code:
 k2pdfopt -mode copy -c- -cmax 3 myfile.pdf
You can increase the cmax value if you like. This worked pretty well on your image. Make the value negative to force it (when it is positive, it just acts as a ceiling--k2pdfopt tries to pick an optimum).
Edit #1: See attachment for your sample (page 1) and the conversion (page 2).
Edit #2: Out of curiosity, I added to the attachment the default conversion done by Scan Tailor (v0.9.11.1) on page 3.
Attached Files
File Type: pdf file_plus_conversion.pdf (1.10 MB, 83 views)

Last edited by willus; 03-17-2017 at 09:32 PM. Reason: Added / Modified attachment
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Old 03-24-2017, 03:11 PM   #3
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Thank you!
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Old 04-20-2017, 12:47 PM   #4
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Unfortunately, it didn't work for the entire book (or even bigger samples than the one provided), see attachment. It's huge: 3.15GB
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Name:	k2pdfopt-error.png
Views:	59
Size:	23.4 KB
ID:	156278  
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Old 04-21-2017, 12:34 AM   #5
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Quote:
Originally Posted by mike.foster View Post
Unfortunately, it didn't work for the entire book (or even bigger samples than the one provided), see attachment. It's huge: 3.15GB
It doesn't look like the mupdf library is compatible with PDF files over 2 GB in size. You mght have to try using a separate tool (cpdf?) to break that PDF into two smaller files ( < 2 GB). How many pages is it?
[Edit: If practical, can you PM me a link to the smallest sample size you tested that doesn't work?]

Last edited by willus; 04-21-2017 at 09:38 AM.
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Old 04-27-2017, 04:06 PM   #6
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This worked, thanks.

Code:
cpdf barres-1922-deracines.pdf -split -chunk 100 -o barres%%%.pdf 
k2pdfopt -mode copy -c- -cmax 3 barres0*.pdf
Notice full name, not wild card in cpdf ...
Attached Thumbnails
Click image for larger version

Name:	Screen Shot 2017-04-27 at 4.05.07 PM.png
Views:	48
Size:	10.1 KB
ID:	156399   Click image for larger version

Name:	Screen Shot 2017-04-27 at 4.05.17 PM.png
Views:	49
Size:	10.3 KB
ID:	156400  
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Old 04-28-2017, 05:17 PM   #7
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Quote:
Originally Posted by mike.foster View Post
This worked, thanks.

Code:
cpdf barres-1922-deracines.pdf -split -chunk 100 -o barres%%%.pdf 
k2pdfopt -mode copy -c- -cmax 3 barres0*.pdf
Notice full name, not wild card in cpdf ...
How did you go from 524 MB for the source file to 7 MB for the converted file? Are the source images completely uncompressed? How many pages are in each of those files (should be the same...)? Can you run k2pdfopt -i on the source file and post the results?
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