Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

Removal of text highlighting

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Removal of text highlighting

Post by script » 30 Mar 2013, 14:38

Is software availible that can aid int he removal of highlighting after the scan has taken place. Yellow, blue and green highlights are in the book that i am scanning and I would like to get rid of them if possible.


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Re: Removal of text highlighting

Post by cday » 01 Apr 2013, 10:58

If the pages you are scanning are text and possibly line drawings -- but have no halftone illustrations or photos or colour other than the highlighting -- you might try converting the images to grayscale and then using a Levels adjustment, as aggressive as necessary, to remove the highlighting.

If your pages do have halftone illustrations or photos, you could try converting to grayscale and then applying the levels adjustment to selections around areas of highlighted text. That would have to be done manually of course and so could not be included in a batch process, making it more time-consuming.

I'm no expert, but conversion to grayscale followed by a bold levels adjustment worked on some test images I created in a paint program, although they may not be representative of your real-world images. There may also be other possible approaches.

If the basic method does show promise with your images, an issue that may arise is that any anti-aliasing -- smoothing of the text edges -- in the original images will have been reduced or lost entirely. If you are scanning, the text quality could be recovered by scanning at a higher dpi, although that would take longer and produce a larger file size, although if the resulting images are then converted to black and white and saved as TIFFs with Fax CCITT-G4 compression they should be very small. When photographing, presumably the original images wouldn't be anti-aliased, so there should be no problem.

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