The Formulas Rendering Plug-In for the Gimp 2 is a
simple plugin that 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.).
