8000 Add Variable buffer class by dr-jts · Pull Request #495 · locationtech/jts · GitHub
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Add Variable buffer class #495

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Merged
merged 3 commits into from
Nov 20, 2019
Merged

Add Variable buffer class #495

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13f565e
Initial commit of VariableBuffer
dr-jts Nov 19, 2019
3df3795
Improve variable buffer generation
dr-jts Nov 20, 2019
79a56f3
Code cleanup
dr-jts Nov 20, 2019
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10 changes: 10 additions & 0 deletions modules/app/src/main/java/org/locationtech/jtstest/function/BufferFunctions.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@
import org.locationtech.jts.operation.buffer.BufferParameters;
import org.locationtech.jts.operation.buffer.OffsetCurveBuilder;
import org.locationtech.jts.operation.buffer.OffsetCurveSetBuilder;
import org.locationtech.jts.operation.buffer.VariableBuffer;
import org.locationtech.jts.operation.buffer.validate.BufferResultValidator;
import org.locationtech.jtstest.geomfunction.Metadata;

Expand Down Expand Up @@ -190,4 +191,13 @@ public Geometry map(Geometry g)
public static Geometry bufferAndInverse(Geometry g, double distance) {
return g.buffer(distance).buffer(-distance);
}

@Metadata(description="Buffer a line by a distance varying along the line")
public static Geometry variableBuffer(Geometry line,
@Metadata(title="Start distance")
double startDist,
@Metadata(title="End distance")
double endDist) {
return VariableBuffer.buffer(line, startDist, endDist);
}
}
11 changes: 11 additions & 0 deletions modules/app/src/main/java/org/locationtech/jtstest/function/LineSegmentFunctions.java
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Expand Up @@ -95,4 +95,15 @@ public static Geometry lineIntersectionDD(Geometry g1, Geometry g2)
return g1.getFactory().createPoint(intPt);
}

public static Geometry reflectPoint(Geometry g1, Geometry g2)
{
Coordinate[] line = g1.getCoordinates();
Coordinate pt = g2.getCoordinate();

LineSegment seg = new LineSegment(line[0], line[1]);
Coordinate reflectPt = seg.reflect(pt);

return g1.getFactory().createPoint(reflectPt);
}

}
26 changes: 26 additions & 0 deletions modules/core/src/main/java/org/locationtech/jts/geom/LineSegment.java
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Expand Up @@ -444,6 +444,32 @@ public LineSegment project(LineSegment seg)

return new LineSegment(newp0, newp1);
}

/**
* Computes the reflection of a point in the line defined
* by this line segment.
*
* @param p the point to reflect
* @return the reflected point
*/
public Coordinate reflect(Coordinate p) {
// general line equation
double A = p1.getY() - p0.getY();
double B = p0.getX() - p1.getX();
double C = p0.getY() * (p1.getX() - p0.getX()) - p0.getX()*( p1.getY() - p0.getY() );

// compute reflected point
double A2plusB2 = A*A + B*B;
double A2subB2 = A*A - B*B;

double x = p.getX();
double y = p.getY();
double rx = ( -A2subB2*x - 2*A*B*y - 2*A*C ) / A2plusB2;
double ry = ( A2subB2*y - 2*A*B*x - 2*B*C ) / A2plusB2;

return new Coordinate(rx, ry);
}

/**
* Computes the closest point on this line segment to another point.
* @param p the point to find the closest point to
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