toucanmeister / prettify

Prettify is a simple command-line based scanned document enhancer created as a project for the course "Algorithm Engineering" in the winter semester of 2021/2022 at the FSU Jena.

prettify

Prettify is a simple command-line based scanned document enhancer created as a project for the course "Algorithm Engineering" in the winter semester of 2021/2022 at the FSU Jena. See paper for the accompanying report.

Features

Prettify works with P3 (ASCII-encoded) portable pix map (.ppm) images. To convert to and from this format, I recommend IrfanView or convert on Linux.

Prettify brings 6 routines to edit images you give it:

• Mean Filter: Removes gausssian noise, but blurrs some edges with high radii
• Gauss Filter: Does the same thing as the mean filter but does not create high-frequency artifacts; is a bit slower
• Median Filter: Removes noise, especially salt-and-pepper noise, without blurring as much as mean or gauss filter
• Global Threshold: Removes backgrounds in images with clear brightness separation between fore- and background
• Adaptive Mean Threshold: Removes backgrounds and shadows in text-only images
• Adaptive Gaussian Threshold: Removes backgrounds and shadows in text-only images, sometimes leaves fewer speckles than adaptive mean threshold

A standard call to improve a scanned document image img.ppm would be:

./prettify img.ppm img_out.ppm median threshold_mean 4 10 gauss

In this call prettify:

• reads img.ppm
• applies a median filter with default radius
• applies an adaptive mean threshold with radius 4 and offset 10
• applies a gauss filter with default radius
• writes the finished image to img_out.ppm

Usage

For more information on how to use prettify, run prettify -h or prettify --help.

Installation

Prettify is written in C++ and thus needs to be compiled on your computer. This also means you will need a C++ compiler, CMake and the OpenMP library installed on your PC.

After downloading the source files, use a command line to go into the folder project.

Run the command cmake -B build.

Then run the command cmake --build build.

The usable executable will be at build/prettify.

Tip: To check that the program works correctly, you can test it: Go into the folder build and run ctest.