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142 lines
3.7 KiB
C
142 lines
3.7 KiB
C
/* Libart_LGPL - library of basic graphic primitives
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* Copyright (C) 1999 Raph Levien
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library 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 GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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#include <math.h>
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#include "art_misc.h"
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#include "art_svp.h"
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#include "art_svp_point.h"
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/* Determine whether a point is inside, or near, an svp. */
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/* return winding number of point wrt svp */
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/**
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* art_svp_point_wind: Determine winding number of a point with respect to svp.
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* @svp: The svp.
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* @x: The X coordinate of the point.
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* @y: The Y coordinate of the point.
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*
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* Determine the winding number of the point @x, @y with respect to @svp.
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*
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* Return value: the winding number.
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**/
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int
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art_svp_point_wind (ArtSVP *svp, double x, double y)
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{
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int i, j;
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int wind = 0;
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for (i = 0; i < svp->n_segs; i++)
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{
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ArtSVPSeg *seg = &svp->segs[i];
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if (seg->bbox.y0 > y)
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break;
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if (seg->bbox.y1 > y)
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{
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if (seg->bbox.x1 < x)
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wind += seg->dir ? 1 : -1;
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else if (seg->bbox.x0 <= x)
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{
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double x0, y0, x1, y1, dx, dy;
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for (j = 0; j < seg->n_points - 1; j++)
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{
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if (seg->points[j + 1].y > y)
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break;
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}
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x0 = seg->points[j].x;
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y0 = seg->points[j].y;
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x1 = seg->points[j + 1].x;
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y1 = seg->points[j + 1].y;
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dx = x1 - x0;
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dy = y1 - y0;
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if ((x - x0) * dy > (y - y0) * dx)
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wind += seg->dir ? 1 : -1;
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}
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}
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}
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return wind;
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}
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/**
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* art_svp_point_dist: Determine distance between point and svp.
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* @svp: The svp.
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* @x: The X coordinate of the point.
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* @y: The Y coordinate of the point.
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*
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* Determines the distance of the point @x, @y to the closest edge in
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* @svp. A large number is returned if @svp is empty.
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*
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* Return value: the distance.
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**/
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double
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art_svp_point_dist (ArtSVP *svp, double x, double y)
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{
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int i, j;
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double dist_sq;
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double best_sq = -1;
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for (i = 0; i < svp->n_segs; i++)
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{
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ArtSVPSeg *seg = &svp->segs[i];
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for (j = 0; j < seg->n_points - 1; j++)
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{
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double x0 = seg->points[j].x;
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double y0 = seg->points[j].y;
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double x1 = seg->points[j + 1].x;
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double y1 = seg->points[j + 1].y;
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double dx = x1 - x0;
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double dy = y1 - y0;
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double dxx0 = x - x0;
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double dyy0 = y - y0;
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double dot = dxx0 * dx + dyy0 * dy;
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if (dot < 0)
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dist_sq = dxx0 * dxx0 + dyy0 * dyy0;
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else
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{
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double rr = dx * dx + dy * dy;
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if (dot > rr)
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dist_sq = (x - x1) * (x - x1) + (y - y1) * (y - y1);
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else
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{
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double perp = (y - y0) * dx - (x - x0) * dy;
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dist_sq = perp * perp / rr;
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}
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}
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if (best_sq < 0 || dist_sq < best_sq)
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best_sq = dist_sq;
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}
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}
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if (best_sq >= 0)
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return sqrt (best_sq);
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else
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return 1e12;
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}
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