[R] Fill a polygon with a pattern

[Alberto Monteiro]

What is the simplest (namely: minimum number of libraries or conflicts)
way to fill a polygon with a pattern?

For example, suppose I have (in a graphic file, like a jpeg) the 
drawing of an "X". Then I fill a polygon (like a triangle) with
this pattern, and get something like:

   X  
  XXX
 XXXXX
XXXXXXX

(where the border "X"s could be truncated).

I searched the rimage package, but it seems that there is no
such function.

Alberto Monteiro