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I take a lot of photos of whiteboards, blackboards, and so on for teaching purposes (examples online through May 2010). I'm interested in cleaning them up for archival purposes, preferably using Linux. Commercial products ClearBoard and PhotoNote are priced a little aggressively for my purposes, plus my students would like to have this capability too.

Does anyone know of any good, open source software for

  • Converting photographs to images with just a few colors?
  • Eliminating perspective distortion?
  • Removing unwanted junk from around the edges of an image?

or anything like that? I'm imagining that I start out with a picture of my whiteboard using red and black markers, and I end up with a three-color image using just white, red, and black. Or I photograph a laser-printed document and end up with a clean black-and-white image. I have tried standard tools that reduce the number of colors in an image, and they do a terrible job—probably because they are trying to reproduce the uneven illumination of the original image.

Command-line Linux tools would be ideal.

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Link is broken ;( –  John T Feb 11 '10 at 0:15
    
He forgot a /, better now. –  heavyd Feb 11 '10 at 14:14
    
There's also whiteboard photo from PolyVision, but it is even more pricey than the software you mention. I'm surprised there isn't an open source variant given the large connection between open source and colleges, and the (commendably) lazy nature of college students... –  RBerteig Apr 9 '10 at 0:26
    
Similar question here: superuser.com/questions/75373/… –  Simon Aug 2 '10 at 4:01

7 Answers 7

Here's a blog post describing how to manually clean whiteboard photos in The Gimp.

And here's script that automates a similar process, which can also be invoked from the command line.

I haven't tried either of these myself but they look plausible...

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+1 looks interesting; thanks. We're going to have a student investigate more deeply over the summer... –  Norman Ramsey Apr 9 '10 at 20:17
    
I'm certainly interested if the student's work bears fruit... –  RBerteig Apr 14 '10 at 18:49

Some more sites/companies which can clean up whiteboard images:

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Thanks. The Ricoh option is free and does a reasonably good job - except no perspective correction, and it only does one image at a time. –  Simon Aug 2 '10 at 3:54
2  
All 3 of these links are broken. –  Greg Oct 25 '11 at 10:53
    
I think scanR went away or had problems. Non-open-source on the Mac there's Prizmo (via the app store), use the "Homogenize" feature. –  Mark Bennett Jun 4 '12 at 23:12

I just created a service a few weeks ago: all you need to do is email your whiteboard picture as an attachment, the service cleans it up and emails it back to you.

The service is called Snapclean.me. The email endpoint is doodle@snapclean.me

Yes it's self promotion, it is free, though it doesn't meet all of your criteria at this time, it does brighten / clean up whiteboard pictures.

I hope this helps you get part of the way to where you need to be.

Regards,

Kyle

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I use an iPhone app - there are several, such as WhiteBoard Capture Pro

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If all you want to do is image enhancement and keystone correction, then the other products mentioned will do variously well.

But if you want that AND the ability to edit the content of the image, such rearranging material to make it more organized, replacing handwriting with typed text in place, editing out junk, and importing other imagery in a collage, you have 2 choices:

  1. Full-featured photo editing tools like PhotoShop and Gimp.
  2. The experimental program called ScanScribe from Xerox PARC.

Option 1 tools are overkill for things like editing camera images of notes and whiteboards.

Option 2 is unpolished but is an extension of the PowerPoint UI and when you wrap your head around it it is really quite powerful.

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I use JotNot on my iPhone which is pretty amazing (and only cost $1 for full version I think). Simple image capture, with several processing/correction presets and then export to JPG or multi-page PDF.

Wish there was a Windows version though. :-(

Simon.

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Looking for source code, but we'll check it out; thanks. –  Norman Ramsey Aug 9 '10 at 16:31

When it comes to command-line image processing on Linux, I have to admit ImageMagick is king. It's free and open source, of course :)

It sounds like the main thing you'd like to achieve is sharpening and lessening the amount of colors used in the image.

For example, to convert an image to 256 colors:

convert input.png -colors 256 output.png
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And the perspective distortion could be fixed by "convert -distort Perspective ..." –  njd Feb 11 '10 at 2:27
    
The distortion cannot be fixed automatically, as the pictures could be taken from different angles. The tool should recognize where are the borders of the whiteboard and uses them to align the picture. –  Snark Feb 11 '10 at 13:57
    
256 colors is way too many. If I have a whiteboard and am using red, black, and blue markers, I'd like a tool that reduces the number of colors to four. It turns out just reducing the number of colors using standard tools does a terrible job. Both netpbm and imagemagick try (I suspect) to get the 'best possible approximation' (least mean square error) in the final image. Because of uneven illumination, the results are terrible. I'll look into sharpening. –  Norman Ramsey Feb 12 '10 at 0:02

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