Laser Scanning Results
Posted: 26 Sep 2014, 00:03
Thanks to Chrisoph's (guitarguy) help, I have managed to refine the laser scan postprocessing technique quite a bit. The current method will automatically detect left and right page boundaries, deskew, and dewarp all pages. The only hints you have to give it are to tell it whether it is an odd or even page and whether it is a scan of a single page or a double-page spread. There are still a number of enhancements to look into, but things are good enough now that it is reasonable to start scanning real books with this technique.
To give you an idea of both the power and limitations, here are a few cropped scans comparing the original photo with the dewarped image:
FIrst pair:
Second pair:
Third pair:
As you can see, it handles curved text extremely well. There are still times when there remains a very slight tilt, but it is almost perfect. The weakness is foreshortened text. It stretches out the foreshortening a small amount, but nowhere near enough to pull it back to its original proportions.
Because of this limitation, the technique will be most useful when the operator is holding the book at the edges to minimize foreshortening. It will also work better on smaller books because it is easier to hold their pages straight from the edges.
Using cheap lasers, it is now possible to build a scanner that is extremely simple mechanically but yields good quality scans.
Other links:
The laser-dewarp github if you want to try the current version of the script yourself: https://github.com/duerig/laser-dewarp
Full-resolution scans and dewarped pages used in the above crops:
Image: https://files.app.net/wh25n7-cn
Laser: https://files.app.net/wh25lOiXX
Even Dewarping: https://files.app.net/wh225MxY-
Odd Dewarping: https://files.app.net/wh22wWt6O
Image: https://files.app.net/wh22hkzpz
Laser: https://files.app.net/wh25t9N4D
Even Dewarping: https://files.app.net/wh22zcTp0
Odd Dewarping: https://files.app.net/wh220P92a
If you want to build your own laser rig, have ideas of how to improve things, or have any other questions feel free to ask here.
To give you an idea of both the power and limitations, here are a few cropped scans comparing the original photo with the dewarped image:
FIrst pair:
Second pair:
Third pair:
As you can see, it handles curved text extremely well. There are still times when there remains a very slight tilt, but it is almost perfect. The weakness is foreshortened text. It stretches out the foreshortening a small amount, but nowhere near enough to pull it back to its original proportions.
Because of this limitation, the technique will be most useful when the operator is holding the book at the edges to minimize foreshortening. It will also work better on smaller books because it is easier to hold their pages straight from the edges.
Using cheap lasers, it is now possible to build a scanner that is extremely simple mechanically but yields good quality scans.
Other links:
The laser-dewarp github if you want to try the current version of the script yourself: https://github.com/duerig/laser-dewarp
Full-resolution scans and dewarped pages used in the above crops:
Image: https://files.app.net/wh25n7-cn
Laser: https://files.app.net/wh25lOiXX
Even Dewarping: https://files.app.net/wh225MxY-
Odd Dewarping: https://files.app.net/wh22wWt6O
Image: https://files.app.net/wh22hkzpz
Laser: https://files.app.net/wh25t9N4D
Even Dewarping: https://files.app.net/wh22zcTp0
Odd Dewarping: https://files.app.net/wh220P92a
If you want to build your own laser rig, have ideas of how to improve things, or have any other questions feel free to ask here.