Pads an array with variablethickness.
b (optional) A scalar with which to pad the array; if b is omitted then each pad layer is a copy of its underlying layer.
a = INDGEN( 2, 3 ) & PM, a 0 2 4 1 3 5 PM, PADIT( a ) 0 0 2 4 4 0 0 2 4 4 1 1 3 5 5 1 1 3 5 5 PM, PADIT( a, 6 ) 6 6 6 6 6 6 0 2 4 6 6 1 3 5 6 6 6 6 6 6