Function cannyFrontierFromState

Propagates strong Canny seeds through weak candidates in wavefronts. State values are 0 (background), 1 (weak), and 2 (strong seed). This is the tile-connectivity primitive; NMS remains a separate producer.

void cannyFrontierFromState(
  scope const(ubyte)[] state,
  ulong w,
  ulong h,
  ref ubyte[] edges
) @safe;