This is a simple Java program that, when run, will take in an image file as an argument and create a negative version of that image.
To replace an image with its negative:
$ java -jar pixelpoke.jar [path_to_image.jpg]
To make a photonegative of an image and store it in a new image file:
$ java -jar pixelpoke.jar [path_normal_image.jpg] [path_to_new_image.jpg]
This software is licensed under the GNU GPL, version 3.