/*
* 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.metric.UtilAngle;
import georegression.struct.line.LineGeneral2D_F64;
import georegression.struct.line.LineParametric2D_F64;
import georegression.struct.line.LinePolar2D_F64;
import georegression.struct.line.LineSegment2D_F64;
import georegression.struct.point.Point2D_F64;
/**
* Various functions related to lines
*
* @author Peter Abeles
*/
public class UtilLine2D_F64 {
/**
* Returns the acute angle between the slope of two lines. Lines do not need to ever
* intersect. Found using the dot product.
*
* @param a (input) line
* @param b (input) line
* @return acute angle in radians
*/
public static double acuteAngle( LineGeneral2D_F64 a , LineGeneral2D_F64 b ) {
double la = Math.sqrt(a.A*a.A + a.B*a.B);
double lb = Math.sqrt(b.A*b.A + b.B*b.B);
// numerical round off error can cause it to be barely greater than 1, which is outside the allowed
// domain of acos()
double value = (a.A*b.A + a.B*b.B)/(la*lb);
if( value < -1.0 ) value = -1.0;
else if( value > 1.0 ) value = 1.0;
return Math.acos(value);
}
/**
* Returns the acute angle between the slope of two lines and assumes that the lines have
* been normalized such that A*A + B*B = 1. This avoids the need to compute the square root
* twice. Lines do not need to ever intersect. Found using the dot product.
*
* @param a (input) normalized line
* @param b (input) normalized line
* @return acute angle in radians
*/
public static double acuteAngleN( LineGeneral2D_F64 a , LineGeneral2D_F64 b ) {
double value = a.A*b.A + a.B*b.B;
if( value < -1.0 ) value = -1.0;
else if( value > 1.0 ) value = 1.0;
return Math.acos(value);
}
/**
* Converts a line from polar form to parametric.
*
* @param src (input) line is polar notation
* @param ret (output) line in parametric notation. If null a new instance will be created.
* @return Converted line in parametric notation
*/
public static LineParametric2D_F64 convert( LinePolar2D_F64 src , LineParametric2D_F64 ret )
{
if( ret == null )
ret = new LineParametric2D_F64();
double c = (double) Math.cos(src.angle);
double s = (double) Math.sin(src.angle);
ret.p.set(c*src.distance,s*src.distance);
ret.slope.set(-s,c);
return ret;
}
/**
* Converts a line from polar form to general. After conversion the line will be normalized, e.g. A*A + B*B == 1.
*
* @param src (input) line is polar notation
* @param ret (output) line in general notation. If null a new instance will be created.
* @return Converted line in general notation
*/
public static LineGeneral2D_F64 convert( LinePolar2D_F64 src , LineGeneral2D_F64 ret )
{
if( ret == null )
ret = new LineGeneral2D_F64();
double c = (double) Math.cos(src.angle);
double s = (double) Math.sin(src.angle);
ret.A = c;
ret.B = s;
ret.C = -src.distance;
return ret;
}
/**
* Converts a line from general to polar.
*
* @param src (input) line is general notation
* @param ret (output) line in polar notation. If null a new instance will be created.
* @return Converted line in polar notation
*/
public static LinePolar2D_F64 convert( LineGeneral2D_F64 src , LinePolar2D_F64 ret )
{
if( ret == null )
ret = new LinePolar2D_F64();
double r = Math.sqrt(src.A*src.A + src.B*src.B);
double sign = src.C < 0 ? -1 : 1;
ret.angle = Math.atan2(-sign*src.B/r,-sign*src.A/r);
ret.distance = sign*src.C/r;
return ret;
}
/**
* Converts a line segment into a parametric line. The start point will be 'src.a' and the
* direction will be in the direction of 'src.b-src.a'
*
* @param src (input) line segment
* @param ret (output) line in parametric notation. If null a new instance will be created.
* @return Converted line in parametric notation
*/
public static LineParametric2D_F64 convert( LineSegment2D_F64 src , LineParametric2D_F64 ret )
{
if( ret == null )
ret = new LineParametric2D_F64();
ret.p.set(src.a);
ret.slope.set(src.slopeX(),src.slopeY());
return ret;
}
/**
* Converts a line segment into a general line.
*
* @param src (Input) line segment
* @param ret (output) line in general notation. If null a new instance will be created.
* @return Line in general notation
*/
public static LineGeneral2D_F64 convert( LineSegment2D_F64 src , LineGeneral2D_F64 ret )
{
return convert(src.a,src.b,ret);
}
/**
* Converts a line segment into a general line. Line segment is defined by two points.
*
* @param a (Input) End point of line segment
* @param b (Input) End point of line segment
* @param ret (output) line in general notation. If null a new instance will be created.
* @return Line in general notation
*/
public static LineGeneral2D_F64 convert( Point2D_F64 a , Point2D_F64 b , LineGeneral2D_F64 ret )
{
if( ret == null )
ret = new LineGeneral2D_F64();
ret.A = a.y - b.y;
ret.B = b.x - a.x;
ret.C = -(ret.A*a.x + ret.B*a.y);
return ret;
}
/**
* Converts a line from parametric to polar.
*
* @param src (Input) line in parametric notation
* @param ret (output) line in polar notation. If null a new instance will be created.
* @return Line in polar notation
*/
public static LinePolar2D_F64 convert( LineParametric2D_F64 src , LinePolar2D_F64 ret )
{
if( ret == null )
ret = new LinePolar2D_F64();
double top = src.slope.y*src.p.x - src.slope.x*src.p.y;
ret.distance = top/src.slope.norm();
ret.angle = Math.atan2(-src.slope.x,src.slope.y);
if( ret.distance < 0 ) {
ret.distance = -ret.distance;
ret.angle = UtilAngle.bound(ret.angle + Math.PI);
}
return ret;
}
/**
* Converts a line from parametric to general
*
* @param src (input) line in parametric notation.
* @param ret (output) line in general notation. If null a new instance will be created.
* @return Converted line in general notation
*/
public static LineGeneral2D_F64 convert( LineParametric2D_F64 src , LineGeneral2D_F64 ret ) {
if( ret == null ) {
ret = new LineGeneral2D_F64();
}
ret.A = -src.slope.y;
ret.B = src.slope.x;
ret.C = -ret.A*src.p.x - ret.B*src.p.y;
return ret;
}
/**
* Converts a line from general to parametric
*
* @param src (input) line in general notation.
* @param ret (output) line in parametric notation. If null a new instance will be created.
* @return Converted line in parametric notation
*/
public static LineParametric2D_F64 convert( LineGeneral2D_F64 src , LineParametric2D_F64 ret ) {
if( ret == null ) {
ret = new LineParametric2D_F64();
}
ret.slope.x = src.B;
ret.slope.y = -src.A;
// find a point on the line
if( Math.abs(src.B) > Math.abs(src.A) ) {
ret.p.y = -src.C/src.B;
ret.p.x = 0;
} else {
ret.p.x = -src.C/src.A;
ret.p.y = 0;
}
return ret;
}
}
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