////  FloodFill.h//  libraries/shared/src////  Copyright 2013 High Fidelity, Inc.////  Distributed under the Apache License, Version 2.0.//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html// #ifndef hifi_FloodFill_h#define hifi_FloodFill_h // // Line scanning, iterative flood fill algorithm.//// The strategy must obey the following contract:////   There is an associated cursor that represents a position on the image. //   The member functions 'left(C&)', 'right(C&)', 'up(C&)', and 'down(C&)' //   move it.//   The state of a cursor can be deferred to temporary storage (typically a//   stack or a queue) using the 'defer(C const&)' member function. //   Calling 'deferred(C&)' restores a cursor's state from temporary storage//   and removes it there.//   The 'select(C const&)' and 'process(C const&)' functions control the //   algorithm. The former is called to determine where to go. It may be//   called multiple times but does not have to (and should not) return //   'true' more than once for a pixel to be selected (will cause memory//   overuse, otherwise). The latter will never be called for a given pixel//   unless previously selected. It may be called multiple times, in which//   case it should return 'true' upon successful processing and 'false'//   when an already processed pixel has been visited. // // Note: The terms "image" and "pixel" are used for illustratory purposes// and mean "undirected graph with 4-connected 2D grid topology" and "node",// respectively.//template< class Strategy, typename Cursor >void floodFill(Cursor const& position,        Strategy const& strategy = Strategy());  template< class Strategy, typename Cursor > struct floodFill_impl : Strategy {     floodFill_impl(Strategy const& s) : Strategy(s) { }     using Strategy::select;    using Strategy::process;     using Strategy::left;    using Strategy::right;    using Strategy::up;    using Strategy::down;     using Strategy::defer;    using Strategy::deferred;     void go(Cursor position) {         if (! select(position)) {            return;        }         Cursor higher, lower, h,l, i;        do {             if (! process(position)) {                continue;            }             higher = position;            up(higher);             if (select(higher)) { defer(higher); }             lower = position;            down(lower);            if (select(lower)) { defer(lower); }             i = position, h = higher, l = lower;            do {                 right(i), right(h), right(l);                 if (select(h)) { defer(h); }                if (select(l)) { defer(l); }             } while (select(i) && process(i));             i = position, h = higher, l = lower;            do {                left(i); left(h); left(l);                 if (select(h)) { defer(h); }                if (select(l)) { defer(l); }             } while (select(i) && process(i));         } while (deferred(position));    }}; template< class Strategy, typename Cursor >void floodFill(Cursor const& p, Strategy const& s) {     floodFill_impl<Strategy,Cursor>(s).go(p);}  #endif // hifi_FloodFill_h