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

First build with automatic dewarping

Scan Tailor specific announcements, releases, workflows, tips, etc. NO FEATURE REQUESTS IN THIS FORUM, please.
Tulon
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Re: First build with automatic dewarping

Post by Tulon » 03 Feb 2011, 17:51

Tulon wrote:Does this mean that software like qprc (http://diybookscanner.org/forum/viewtopic.php?f=3&t=784), PhotoShop or DxO are useless and that is better to do de-keystonne in ScanTailor?
Scan Tailor and any other software use the same mathematical model for dekeystoning - it's called homographic transformation. However, there are a couple of reasons you may want to correct keystoning before Scan Tailor:
1. Programs relying on pre-calibration (with a checkboard pattern, QR codes, etc.) won't generally make mistakes.
2. Content box and margins don't play well with significant keystoning, so either prepare for more manual adjustments or do your dekeystoning before Scan Tailor.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

zamacam
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Re: First build with automatic dewarping

Post by zamacam » 03 Feb 2011, 19:21

Thank you for this interesting answer Tulon. Even if I'm working in a law deparment, I'm working with programers and it is always interesting to understand how the magic works :-)

By the way, I had to say that Beta 9 works fine here. The only problem I have was examined here http://diybookscanner.org/forum/viewtopic.php?f=8&t=642 but it is over my skills to understand if it is a Qt's problem or a ScanTailor's one and even far my skills to understand if n9yty have found a workaround.

steve1066d
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Re: First build with automatic dewarping

Post by steve1066d » 03 Feb 2011, 19:31

Knk,

You might want to take a look at BookScanWizard. It can crop and dekeystone.

In your case, you'd want to copy your images to a l & r directory, then use the Perspective and Crop commands. You can fix the width of the document by either using the optional height & width commands of the Perspective command, or else using the Scale command.
Steve Devore
BookScanWizard, a flexible book post-processor.

Tulon
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Re: First build with automatic dewarping

Post by Tulon » 22 Feb 2011, 18:10

I thought I'd give you an update on what I am currently working on. That would be tracing top / bottom page edges, where available. The main complexity here is tracing the right thing:
right_trace.jpg
right_trace.jpg (21.04 KiB) Viewed 3430 times
Not the wrong one:
wrong_trace.jpg
wrong_trace.jpg (19.02 KiB) Viewed 3430 times
As you can see, I made some good progress. Still, there is a lot of of work ahead.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

ahmad
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Re: First build with automatic dewarping

Post by ahmad » 22 Feb 2011, 18:18

Wowzers!

So is this an alternative to line-based dewarping, a complement to it, or a replacement of it?

Tulon
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Re: First build with automatic dewarping

Post by Tulon » 22 Feb 2011, 18:37

ahmad wrote:So is this an alternative to line-based dewarping, a complement to it, or a replacement of it?
A complement. The traced vertical boundaries will be treated exactly the same as traced text lines. After all, we aren't after specifically text lines. We are after anything that's long and horizontal on the flat page.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

matt

Re: First build with automatic dewarping

Post by matt » 23 Feb 2011, 04:27

oh, this sounds like great news about the edge tracing efforts. i'm very excited to see your progress with this, tulon.

do you expect this technique to significantly improve the accuracy of the dewarping on problematic pages (eg pages with non-rectangular text areas)? would a successful implementation reduce the need for de-keystoning preprocessing?

thanks again for all the work!
matt

Tulon
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Re: First build with automatic dewarping

Post by Tulon » 23 Feb 2011, 04:59

matt wrote:do you expect this technique to significantly improve the accuracy of the dewarping on problematic pages (eg pages with non-rectangular text areas)?
Yes, it's going to help such pages.
matt wrote:would a successful implementation reduce the need for de-keystoning preprocessing?
Dekeystoning is a special case of dewarping. If dewarping works well, it will dekeystone just as well. However, as I mentioned before, Content Box and Margins stages are not friendly to strongly keystoned pages, which is the reason you may want to dekeystone in a separate program.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

spamsickle
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Re: First build with automatic dewarping

Post by spamsickle » 04 Mar 2011, 17:25

I'm having a problem with the "apply to" for the dewarping. I have some images with mild keystoning on the left-hand pages. I go through and control-click every other image to select them, then modify the manual warp grid to correct the first one. I check "apply to selected images", but the apply doesn't seem to be propagating. I'm running the CLI version, which I've compiled without modification.

Tulon
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Re: First build with automatic dewarping

Post by Tulon » 04 Mar 2011, 17:47

You are only applying dewarping mode (off, manual, auto). Applying the grid itself is not implemented, as I don't think that will work well enough.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

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