Skip the sort and pass the source through (premultiplied).
Which end of a run the bright pixels gather toward.
Channel ranked within each bright run.
Sort band [lo, hi] in [0,1]. Only pixels whose key lands inside are sorted.
Number of cells the sort axis is divided into. Higher = finer sort.
Sort axis rotation in degrees. Non-zero wraps the sort in a
rotate-in / rotate-out pass pair so the streaks run at any angle.