pdl> p $im

[
 [0 0 1 1 0 0]
 [2 0 0 1 0 0]
 [2 2 0 0 0 3]
 [0 0 0 0 3 0]
]


pdl> p $im-> flat-> qsort # Won't be used. Just a demo.
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 2 2 2 3 3]

pdl> p $idx = $im-> flat-> qsorti
[15 16 14 10 11 21 23 20 18 19 4 5 0 1 7 8 3 2 9 13 6 12 22 17]

pdl> p +( $runs ) = $im-> flat-> qsort -> rle
[16 3 3 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]

pdl> ( $x, $y ) = $im-> one2nd( $idx )

pdl> p $x
[3 4 2 4 5 3 5 2 0 1 4 5 0 1 1 2 3 2 3 1 0 0 4 5]

pdl> p $y
[2 2 2 1 1 3 3 3 3 3 0 0 0 0 1 1 0 0 1 2 1 2 3 2]

pdl> p $idx # NB. Destroyed! 
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]

pdl>