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/* edge.c: operations on edges in bitmaps.
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Copyright (C) 1992 Free Software Foundation, Inc.
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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 2, or (at your option)
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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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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
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* Copyright (C) 1992 Free Software Foundation, Inc.
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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 2, or (at your option)
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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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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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#include "config.h"
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static edge_type next_edge (edge_type);
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/* The following macros are used (directly or indirectly) by the
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`next_outline_edge' routine. */
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`next_outline_edge' routine. */
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/* Given the direction DIR of the pixel to test, decide which edge on
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that pixel we are supposed to test. Because we've chosen the mapping
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`COL'). We are in the ``display'' coordinate system, with y
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increasing downward and x increasing to the right. Therefore, we are
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implementing the following table:
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direction row delta col delta
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with the other four directions (e.g., northwest) being the sum of
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their components (e.g., north + west).
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The first macro, `COMPUTE_DELTA', handles splitting up the latter
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cases, all of which have been assigned odd numbers. */
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#define COMPUTE_DELTA(axis, dir) \
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? COMPUTE_##axis##_DELTA ((dir) - 1) \
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on the current pixel. We want to go around outside outlines
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counterclockwise, and inside outlines clockwise (because that is how
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both Metafont and Adobe Type 1 format want their curves to be drawn).
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The very first outline (an outside one) on each character starts on a
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top edge (STARTING_EDGE in edge.h defines this); so, if we're at a
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top edge, we want to go only to the left (on the pixel to the west)
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or down (on the same pixel), to begin with. Then, when we're on a
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left edge, we want to go to the top edge (on the southwest pixel) or
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to the left edge (on the south pixel).
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All well and good. But if you draw a rasterized circle (or whatever),
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eventually we have to come back around to the beginning; at that
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point, we'll be on a top edge, and we'll have to go to the right edge
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on the northwest pixel. Draw pictures.
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The upshot is, if we find an edge on another pixel, we return (in ROW
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and COL) the position of the new pixel, and (in EDGE) the kind of
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edge it is. If we don't find such an edge, we return (in EDGE) the
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return row == 0 || sel_pixel_is_white(row - 1, col);
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return (col == sel_get_width() - 1)
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return (col == sel_get_width() - 1)
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|| sel_pixel_is_white(row, col + 1);
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return (row == sel_get_height() - 1)
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return (row == sel_get_height() - 1)
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|| sel_pixel_is_white(row + 1, col);
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printf ("is_outline_edge: Bad edge value(%d)", edge);
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return 0; /* NOTREACHED */
added
removed
plug-ins/sel2path/edge.c
