intensity map / plot

Dear R-list,


I would like to generate an intensity map based on a x * y matrix.

Each point in the matrix should get plotted at the coordinate: x = column / y = row with 
a color-intensity (for example gray-value) based on the actual value of this point.

Is there a convenient package / function for this kind of plot?



example data:
x <- matrix(rnorm(100*100, 0, 2), 100, 100)


thanks!