georegression.geometry.polygon.AreaIntersectionPolygon2D_F32 Maven / Gradle / Ivy
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GeoRegression is a free Java based geometry library for scientific computing in fields such as robotics and computer vision with a focus on 2D/3D space.
/*
* Copyright (C) 2020, Peter Abeles. All Rights Reserved.
*
* This file is part of Geometric Regression Library (GeoRegression).
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package georegression.geometry.polygon;
import javax.annotation.Generated;
import georegression.geometry.UtilPolygons2D_F32;
import georegression.struct.point.Point2D_I32;
import georegression.struct.shapes.Polygon2D_F32;
import georegression.struct.shapes.Rectangle2D_F32;
/**
*
* Computes the area of intersection between two convex polygons. Port of code found at [1] and Java version by Lagado.
*
*
* WARNING: No effort has been made to reduce the number of calls to new internally from original code.
*
* [1] http://www.cap-lore.com/MathPhys/IP/
*
* @author Peter Abeles
*/
@SuppressWarnings("NullAway.Init")
@Generated("georegression.geometry.polygon.AreaIntersectionPolygon2D_F64")
public class AreaIntersectionPolygon2D_F32 {
static final float gamut = (float)500000000.0f;
static final float mid = gamut / (float)2.0f;
private long ssss;
private float sclx;
private float scly;
/**
* Computes the area of the intersection between the two polygons.
*
* Note: the area result has little more accuracy than a float
* This is true even if the polygon is specified with floats.
*
* @param a Polygon A
* @param b Polygon B
* @return area of area of intersection. Negative if the order (CW vs CCW) do not match.
*/
public float computeArea(Polygon2D_F32 a , Polygon2D_F32 b ) {
ssss = 0;
sclx = 0;
scly = 0;
return inter(a,b);
}
//--------------------------------------------------------------------------
static class Rng {
int mn; int mx;
Rng(int mn, int mx) { this.mn = mn; this.mx = mx; }
}
static class Vertex { Point2D_I32 ip; Rng rx; Rng ry; int in; }
//--------------------------------------------------------------------------
private static void range(Polygon2D_F32 points, Rectangle2D_F32 bbox)
{
UtilPolygons2D_F32.bounding(points,bbox);
}
private static long area(Point2D_I32 a, Point2D_I32 p, Point2D_I32 q) {
return (long)p.x * q.y - (long)p.y * q.x +
(long)a.x * (p.y - q.y) + (long)a.y * (q.x - p.x);
}
private static boolean ovl(Rng p, Rng q) {
return p.mn < q.mx && q.mn < p.mx;
}
private void cntrib(int f_x, int f_y, int t_x, int t_y, int w) {
ssss += (long)w * (t_x - f_x) * (t_y + f_y) / 2;
}
private void fit(Polygon2D_F32 x, Vertex[] ix, int fudge, Rectangle2D_F32 B)
{
int c = x.size();
while (c-- > 0) {
ix[c] = new Vertex();
ix[c].ip = new Point2D_I32();
ix[c].ip.x = ((int)((x.get(c).getX() - B.p0.x) * sclx - mid) & ~7)
| fudge | (c & 1);
ix[c].ip.y = ((int)((x.get(c).getY() - B.p0.y) * scly - mid) & ~7)
| fudge;
}
ix[0].ip.y += x.size() & 1;
ix[x.size()] = ix[0];
c = x.size();
while (c-- > 0) {
ix[c].rx = ix[c].ip.x < ix[c + 1].ip.x ?
new Rng(ix[c].ip.x, ix[c + 1].ip.x) :
new Rng(ix[c + 1].ip.x, ix[c].ip.x);
ix[c].ry = ix[c].ip.y < ix[c + 1].ip.y ?
new Rng(ix[c].ip.y, ix[c + 1].ip.y) :
new Rng(ix[c + 1].ip.y, ix[c].ip.y);
ix[c].in = 0;
}
}
private void cross(Vertex a, Vertex b, Vertex c, Vertex d,
float a1, float a2, float a3, float a4)
{
float r1 = a1 / ((float) a1 + a2);
float r2 = a3 / ((float) a3 + a4);
cntrib((int)(a.ip.x + r1 * (b.ip.x - a.ip.x)),
(int)(a.ip.y + r1 * (b.ip.y - a.ip.y)),
b.ip.x, b.ip.y, 1);
cntrib(d.ip.x, d.ip.y,
(int)(c.ip.x + r2 * (d.ip.x - c.ip.x)),
(int)(c.ip.y + r2 * (d.ip.y - c.ip.y)),
1);
++a.in;
--c.in;
}
private void inness(Vertex[] P, int cP, Vertex[] Q, int cQ)
{
int s = 0;
int c = cQ;
Point2D_I32 p = P[0].ip;
while (c-- > 0) {
if (Q[c].rx.mn < p.x && p.x < Q[c].rx.mx) {
boolean sgn = 0 < area(p, Q[c].ip, Q[c + 1].ip);
s += (sgn != Q[c].ip.x < Q[c + 1].ip.x) ? 0 : (sgn ? -1 : 1);
}
}
for (int j = 0; j < cP; ++j) {
if (s != 0)
cntrib(P[j].ip.x, P[j].ip.y,
P[j + 1].ip.x, P[j + 1].ip.y, s);
s += P[j].in;
}
}
//-------------------------------------------------------------------------
private float inter(Polygon2D_F32 a, Polygon2D_F32 b)
{
if (a.size() < 3 || b.size() < 3)
return 0;
// int na = a.size();
// int nb = b.size();
Vertex[] ipa = new Vertex[a.size() + 1];
Vertex[] ipb = new Vertex[b.size()+ 1];
Rectangle2D_F32 bbox = new Rectangle2D_F32(
Float.MAX_VALUE, Float.MAX_VALUE,
-Float.MAX_VALUE, -Float.MAX_VALUE);
range(a, bbox);
range(b, bbox);
float rngx = bbox.p1.x - bbox.p0.x;
sclx = gamut / rngx;
float rngy = bbox.p1.y - bbox.p0.y;
scly = gamut / rngy;
float ascale = sclx * scly;
fit(a, ipa, 0, bbox);
fit(b, ipb, 2, bbox);
for (int j = 0; j < a.size(); ++j) {
for (int k = 0; k < b.size(); ++k) {
if (ovl(ipa[j].rx, ipb[k].rx) && ovl(ipa[j].ry, ipb[k].ry)) {
long a1 = -area(ipa[j].ip, ipb[k].ip, ipb[k + 1].ip);
long a2 = area(ipa[j + 1].ip, ipb[k].ip, ipb[k + 1].ip);
boolean o = a1 < 0;
if (o == a2 < 0) {
long a3 = area(ipb[k].ip, ipa[j].ip, ipa[j + 1].ip);
long a4 = -area(ipb[k + 1].ip, ipa[j].ip,
ipa[j + 1].ip);
if (a3 < 0 == a4 < 0) {
if (o)
cross(ipa[j], ipa[j + 1], ipb[k], ipb[k + 1],
a1, a2, a3, a4);
else
cross(ipb[k], ipb[k + 1], ipa[j], ipa[j + 1],
a3, a4, a1, a2);
}
}
}
}
}
inness(ipa, a.size(), ipb, b.size());
inness(ipb, b.size(), ipa, a.size());
return ssss / ascale;
}
}