This simple plugin allows you to change the values of each color channel of each pixel of a layer by using mathematical expressions.
It is able to handle RGB* and Gray* images. Available operators are: +, -, *, /, , and %.
There are many functions available, such as sin, cos, sqrt, abs, min, max.
A few constants are provided (pi, e, j), and a lot of pre-defined variables are usable (w for image's width, h for image's height, x and y for cartesian coordinates in the image, etc.).