This returns the color in the MAP file at the location (X,Y).
MAP is the filename of the map file.
X   is the x coordinate of the location into the map.
Y   is the y coordinate of the location into the map.

This must be the path of a color image file.
This is a constant file name. As a constant, 
it cannot accept inputs, since it may not be procedually set.
This value also may not become an argument to the shader 
for the same reason.

This must be a scalar.  This is the x location into the map.

This must be a scalar.  This is the y location into the map.

This is the color returned.