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https://github.com/unpaper/unpaper

A post-processing tool for scanned sheets of paper.
https://github.com/unpaper/unpaper

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A post-processing tool for scanned sheets of paper.

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README 

        



unpaper

=======



Originally written by Jens Gulden — see AUTHORS for more information.

The entire `unpaper` project is licensed under GNU GPL v2.

Some of the individual files are licensed under the MIT or Apache 2.0 licenses.

Each file contains an [SPDX license header](https://reuse.software/)

specifying its license. The text of all three licenses is available under

`LICENSES`.



Overview

--------



`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 misaligned 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.



See [further documentation][3] for the supported file formats notes.



Dependencies

------------



The only hard dependency of `unpaper` is [ffmpeg][4], which is used for

file input and output.



Building instructions

---------------------



`unpaper` uses [the Meson Build system](https://mesonbuild.com), which

can be installed using Python's package manage (`pip3` or `pip`):



    unpaper$ pip3 install --user 'meson >= 0.57' 'sphinx >= 3.4'

    unpaper$ CFLAGS="-march=native" meson --buildtype=debugoptimized builddir

    unpaper$ meson compile -C builddir



You can pass required optimization flags when creating the meson build

directory in the `CFLAGS` environment variable. Usage of Link-Time

Optimizations (Meson option `-Db_lto=true`) is recommended if

available.



Further optimizations such as `-ftracer` and `-ftree-vectorize` are

thought to work, but their effect has not been evaluated so your

mileage may vary.



Tests depend on `pytest` and `pillow`, which will be auto-detected by

Meson.



Development Hints

-----------------



The project includes configuration for [pre-commit](https://pre-commit.com/)

which is integrated with GitHub Actions CI. If you're using git for

devleopment, you can install it with

`pip install pre-commit && pre-commit --install`.



Using [Sapling](https://sapling-scm.com/) with this repository is possible

and diffs can be reviewed as a stack.



Further Information

-------------------



You can find more information on the [basic concepts][1] and the

[image processing][2] in the available documentation.



[1]: doc/basic-concepts.md

[2]: doc/image-processing.md

[3]: doc/file-formats.md

[4]: https://www.ffmpeg.org/