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