Library containing various image processing algorithms.

Available algorithms:
* Unpaper's algorithms
  * Blackfilter
  * Noisefilter
  * Blurfilter
  * Masks
  * Grayfilter
  * Border
* Canny edge detection
* Sobel operator
* Gaussian blur
* ACE (Automatic Color Equalization ; Parallelized implementation)
* SWT (Stroke Width Transformation)
* Compare: Compare two images (grayscale) and makes the pixels that are
  different really visible (red).

WWW: https://gitlab.gnome.org/World/OpenPaperwork/libpillowfight