/*
* Copyright (C) 2011-2015, 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;
import georegression.geometry.algs.AndrewMonotoneConvexHull_F64;
import georegression.struct.point.Point2D_F64;
import georegression.struct.shapes.Polygon2D_F64;
import georegression.struct.shapes.Quadrilateral_F64;
import georegression.struct.shapes.Rectangle2D_F64;
import georegression.struct.shapes.RectangleLength2D_I32;
import java.util.List;
/**
* Various functions related to polygons.
*
* @author Peter Abeles
*/
public class UtilPolygons2D_F64 {
/**
* Determines if the polugon is convex or concave.
*
* @param poly Polygon
* @return true if convex and false if concave
*/
public static boolean isConvex( Polygon2D_F64 poly ) {
// if the cross product of all consecutive triples is positive or negative then it is convex
final int N = poly.size();
int numPositive = 0;
for (int i = 0; i < N; i++) {
int j = (i+1)%N;
int k = (i+2)%N;
Point2D_F64 a = poly.vertexes.data[i];
Point2D_F64 b = poly.vertexes.data[j];
Point2D_F64 c = poly.vertexes.data[k];
double dx0 = a.x-b.x;
double dy0 = a.y-b.y;
double dx1 = c.x-b.x;
double dy1 = c.y-b.y;
double z = dx0 * dy1 - dy0 * dx1;
if( z > 0 )
numPositive++;
// z can be zero if there are duplicate points.
// not sure if it should throw an exception if its "bad" or not
}
return( numPositive == 0 || numPositive == N );
}
/**
* Converts a rectangle into a quadrilateral
*
* @param input Rectangle.
* @param output Quadrilateral. Modified.
*/
public static void convert( Rectangle2D_F64 input , Quadrilateral_F64 output ) {
output.a.x = input.p0.x;
output.a.y = input.p0.y;
output.b.x = input.p1.x;
output.b.y = input.p0.y;
output.c.x = input.p1.x;
output.c.y = input.p1.y;
output.d.x = input.p0.x;
output.d.y = input.p1.y;
}
/**
* Converts a rectangle into a polygon
*
* @param input Rectangle.
* @param output Polygon2D_F64. Modified.
*/
public static void convert( Rectangle2D_F64 input , Polygon2D_F64 output ) {
if (output.size() != 4)
throw new IllegalArgumentException("polygon of order 4 expected");
output.get(0).set(input.p0.x, input.p0.y);
output.get(1).set(input.p1.x, input.p0.y);
output.get(2).set(input.p1.x, input.p1.y);
output.get(3).set(input.p0.x, input.p1.y);
}
/**
* Converts a quadrilateral into a polygon
*
* @param input Quadrilateral.
* @param output Polygon2D_F64. Modified.
*/
public static void convert( Quadrilateral_F64 input , Polygon2D_F64 output ) {
if (output.size() != 4)
throw new IllegalArgumentException("polygon of order 4 expected");
output.get(0).set(input.a);
output.get(1).set(input.b);
output.get(2).set(input.c);
output.get(3).set(input.d);
}
/**
* Converts a polygon into a quadrilateral
*
* @param input polygon.
* @param output Quadrilateral. Modified.
*/
public static void convert( Polygon2D_F64 input , Quadrilateral_F64 output ) {
if( input.size() != 4 )
throw new IllegalArgumentException("Expected 4-sided polygon as input");
output.a.set(input.get(0));
output.b.set(input.get(1));
output.c.set(input.get(2));
output.d.set(input.get(3));
}
/**
* Converts a rectangle into a quadrilateral
*
* @param input Rectangle.
* @param output Quadrilateral. Modified.
*/
public static void convert( RectangleLength2D_I32 input , Quadrilateral_F64 output ) {
output.a.x = input.x0;
output.a.y = input.y0;
output.b.x = input.x0+input.width-1;
output.b.y = input.y0;
output.c.x = input.x0+input.width-1;
output.c.y = input.y0+input.height-1;
output.d.x = input.x0;
output.d.y = input.y0+input.height-1;
}
/**
* Finds the minimum area bounding rectangle around the quadrilateral.
*
* @param quad (Input) Quadrilateral
* @param rectangle (Output) Minimum area rectangle
*/
public static void bounding( Quadrilateral_F64 quad , Rectangle2D_F64 rectangle ) {
rectangle.p0.x = Math.min(quad.a.x,quad.b.x);
rectangle.p0.x = Math.min(rectangle.p0.x,quad.c.x);
rectangle.p0.x = Math.min(rectangle.p0.x,quad.d.x);
rectangle.p0.y = Math.min(quad.a.y,quad.b.y);
rectangle.p0.y = Math.min(rectangle.p0.y,quad.c.y);
rectangle.p0.y = Math.min(rectangle.p0.y,quad.d.y);
rectangle.p1.x = Math.max(quad.a.x,quad.b.x);
rectangle.p1.x = Math.max(rectangle.p1.x,quad.c.x);
rectangle.p1.x = Math.max(rectangle.p1.x,quad.d.x);
rectangle.p1.y = Math.max(quad.a.y,quad.b.y);
rectangle.p1.y = Math.max(rectangle.p1.y,quad.c.y);
rectangle.p1.y = Math.max(rectangle.p1.y,quad.d.y);
}
/**
* Computes the center or average point in the quadrilateral.
*
* @param quad (Input) Quadrilateral
* @param center (output) Center point of the quadrilateral. Can be null.
* @return The center point.
*/
public static Point2D_F64 center( Quadrilateral_F64 quad , Point2D_F64 center ) {
if( center == null )
center = new Point2D_F64();
center.x = quad.a.x + quad.b.x + quad.c.x + quad.d.x;
center.y = quad.a.y + quad.b.y + quad.c.y + quad.d.y;
center.x /= 4.0;
center.y /= 4.0;
return center;
}
/**
* Returns true if the polygon is ordered in a counter-clockwise order. This is done by summing up the interior
* angles.
*
* @param polygon List of ordered points which define a polygon
* @return true if CCW and false if CW
*/
public static boolean isCCW( List polygon ) {
final int N = polygon.size();
int sign = 0;
for (int i = 0; i < N; i++) {
int j = (i+1)%N;
int k = (i+2)%N;
Point2D_F64 a = polygon.get(i);
Point2D_F64 b = polygon.get(j);
Point2D_F64 c = polygon.get(k);
double dx0 = a.x-b.x;
double dy0 = a.y-b.y;
double dx1 = c.x-b.x;
double dy1 = c.y-b.y;
double z = dx0 * dy1 - dy0 * dx1;
if( z > 0 )
sign++;
else
sign--;
}
return sign < 0;
}
public static boolean isCCW( Polygon2D_F64 polygon ) {
return isCCW(polygon.vertexes.toList());
}
/**
* Computes the average of all the vertexes
* @param input (input) polygon
* @param average (output) average point
*/
public static void vertexAverage(Polygon2D_F64 input, Point2D_F64 average ) {
average.set(0,0);
for (int i = 0; i < input.size(); i++) {
Point2D_F64 v = input.vertexes.data[i];
average.x += v.x;
average.y += v.y;
}
average.x /= input.size();
average.y /= input.size();
}
/**
* Checks to see if the vertexes of the two polygon's are the same up to the specified tolerance
*
* @param a Polygon
* @param b Polygon
* @param tol tolerance
* @return true if identical up to tolerance or false if not
*/
public static boolean isIdentical( Polygon2D_F64 a , Polygon2D_F64 b , double tol ) {
if( a.size() != b.size())
return false;
double tol2 = tol*tol;
for (int i = 0; i < a.size(); i++) {
if( a.get(i).distance2(b.get(i)) > tol2 )
return false;
}
return true;
}
/**
* Checks to see if the vertexes of the two polygon's are the same up to the specified tolerance and allows
* for a shift in their order
*
* @param a Polygon
* @param b Polygon
* @param tol tolerance
* @return true if identical up to tolerance or false if not
*/
public static boolean isEquivalent( Polygon2D_F64 a , Polygon2D_F64 b , double tol ) {
if( a.size() != b.size())
return false;
double tol2 = tol*tol;
// first find two vertexes which are the same
Point2D_F64 a0 = a.get(0);
int match = -1;
for (int i = 0; i < b.size(); i++) {
if( a0.distance2(b.get(i)) <= tol2 ) {
match = i;
break;
}
}
if( match < 0 )
return false;
// now go in a circle and see if they all line up
for (int i = 1; i < b.size(); i++) {
Point2D_F64 ai = a.get(i);
Point2D_F64 bi = b.get((match+i)%b.size());
if( ai.distance2(bi) > tol2 ) {
return false;
}
}
return true;
}
/**
* Flips the order of points inside the polygon. The first index will remain the same will otherwise be reversed
*
* @param a Polygon of order 3 or more.
*/
public static void flip( Polygon2D_F64 a ) {
int N = a.size();
int H = N/2;
for (int i = 1; i <= H; i++) {
int j = N-i;
Point2D_F64 tmp = a.vertexes.data[i];
a.vertexes.data[i] = a.vertexes.data[j];
a.vertexes.data[j] = tmp;
}
}
/**
* Shifts all the vertexes in the polygon up one element. Wraps around at the end
* @param a Polygon
*/
public static void shiftUp( Polygon2D_F64 a ) {
final int N = a.size();
Point2D_F64 first = a.get(0);
for (int i = 0; i < N-1; i++ ) {
a.vertexes.data[i] = a.vertexes.data[i+1];
}
a.vertexes.data[N-1] = first;
}
/**
* Shifts all the vertexes in the polygon up one element. Wraps around at the end
* @param a Polygon
*/
public static void shiftDown( Polygon2D_F64 a ) {
final int N = a.size();
Point2D_F64 last = a.get(N-1);
for (int i = N-1; i > 0; i-- ) {
a.vertexes.data[i] = a.vertexes.data[i-1];
}
a.vertexes.data[0] = last;
}
/**
* Computes the convex hull of the set of points.
*
*
* NOTE: This method declares a temporary array. If you want to avoid that invoke {@link AndrewMonotoneConvexHull_F64}
* directly.
*
*
* @param points (Input) Set of points.
* @param hull (output) storage for convex hull. Will be in counter-clockwise order
*/
public static void convexHull( List points , Polygon2D_F64 hull ) {
Point2D_F64[] array = new Point2D_F64[points.size()];
for (int i = 0; i < points.size(); i++) {
array[i] = points.get(i);
}
AndrewMonotoneConvexHull_F64 andrew = new AndrewMonotoneConvexHull_F64();
andrew.process(array,array.length,hull);
}
}
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