libmousetrap is a C library for the creation and
manipulation of compressed, integer-precision 2D
cartesian grids populated by integer identifiers.
This makes figuring out what is occupying position
(x, y) at any given instant easy. Addition of new
types of sources for creating these grids from
image/graphics libraries is also easy.
libmousetrap fully supports transparent regions in
the grid system. It was created to provide easy
dispatch of mouse events, but seems like it could
have other applications.