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/* edge.h: declarations for edge traversing.
*
* Copyright (C) 1992 Free Software Foundation, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef EDGE_H
#define EDGE_H
#include "bitmap.h"
/* We consider each pixel to consist of four edges, and we travel along
edges, instead of through pixel centers. This is necessary for those
unfortunate times when a single pixel is on both an inside and an
outside outline.
The numbers chosen here are not arbitrary; the code that figures out
which edge to move to depends on particular values. See the
`TRY_PIXEL' macro in `edge.c'. To emphasize this, I've written in the
numbers we need for each edge value. */
typedef enum
{
top = 1, left = 2, bottom = 3, right = 0, no_edge = 4
} edge_type;
/* This choice is also not arbitrary: starting at the top edge makes the
code find outside outlines before inside ones, which is certainly
what we want. */
#define START_EDGE top
/* Return the next outline edge on B in EDGE, ROW, and COL. */
extern void next_outline_edge (edge_type *edge,
unsigned *row, unsigned *col);
/* Return the next edge after START on the pixel ROW/COL in B that is
unmarked, according to the MARKED array. */
extern edge_type next_unmarked_outline_edge (unsigned row, unsigned col,
edge_type start,
bitmap_type marked);
/* Mark the edge E at the pixel ROW/COL in MARKED. */
extern void mark_edge (edge_type e, unsigned row, unsigned col,
bitmap_type *marked);
#endif /* not EDGE_H */
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