unpaper is a post-processing tool for scanned sheets of paper,
especially for book pages that have been scanned from previously
created photocopies. The main purpose is to make scanned book pages
better readable on screen after conversion to PDF. Additionally,
unpaper might be useful to enhance the quality of scanned pages before
performing optical character recognition (OCR). unpaper tries to clean
scanned images by removing dark edges that appeared through scanning
or copying on areas outside the actual page content (e.g. dark areas
between the left-hand-side and the right-hand-side of a double-sided
book-page scan). The program also tries to detect disaligned
centering and rotation of pages and will automatically straighten
each page by rotating it to the correct angle. This process is called
"deskewing". Note that the automatic processing will sometimes fail.
It is always a good idea to manually control the results of unpaper
and adjust the parameter settings according to the requirements of
the input. Each processing step can also be disabled individually
for each sheet. Input and output files can be in either .pbm, .pgm or
.ppm format, thus generally in .pnm format, as also used by the Linux
scanning tools scanimage and scanadf. Conversion to PDF can e.g. be
achieved with the Linux tools pgm2tiff, tiffcp and tiff2pdf.

This is a fork of the original unpaper software by D.E. "Flameeyes"
Petteno'.