Application: gvSIG desktop

import org.gvsig.expressionevaluator.impl.function.spatial.ConvexTrapezoidLengthFunction;

        this.addFunction(new PointByAngleFunction());

        this.addFunction(new ConvexTrapezoidLengthFunction());

package org.gvsig.expressionevaluator.impl.function.spatial;

import org.apache.commons.lang3.Range;

import org.gvsig.euclidean.EuclideanManager;

import org.gvsig.expressionevaluator.Interpreter;

import org.gvsig.expressionevaluator.spi.AbstractGeometryFunction;

import org.gvsig.fmap.geom.Geometry;

import org.gvsig.fmap.geom.primitive.Polygon;

import org.gvsig.tools.util.ToolsUtilLocator;

public class ConvexTrapezoidLengthFunction extends AbstractGeometryFunction {

    public ConvexTrapezoidLengthFunction() {

        super("Spatial", "ConvexTrapezoidLength", Range.is(1));

    }

    @Override

    public boolean allowConstantFolding() {

        return true;

    }

    @Override

    public Object call(Interpreter interpreter, Object[] args) throws Exception {

        Geometry arg1 = (Geometry) getObject(args, 0);

        if( arg1==null ) {

            return null;

        }

        try {

            return convexTrapezoidLength((Polygon) arg1);

        } catch(Exception ex) {

            return null;

        }

    }

    public static double convexTrapezoidLength(Polygon geom) {

        EuclideanManager manager = ToolsUtilLocator.getEuclideanManager();

        if( geom.getNumInteriorRings()!=0 ) {

            throw new IllegalArgumentException("Can't calculate convex trapezoid length if the polygon has interior rings");

        }

        if( geom.isClosed() ) {

            if( geom.getNumVertices()!=5 ) {

                throw new IllegalArgumentException("Wrong number of sides, a convex trapezoid is required");

            }

        } else {

            if( geom.getNumVertices()!=4 ) {

                throw new IllegalArgumentException("Wrong number of sides, a convex trapezoid is required");

            }

        }

        double l[] = new double[4];

        l[0] = manager.distance(

                geom.getCoordinateAt(0, Geometry.DIMENSIONS.X),

                geom.getCoordinateAt(0, Geometry.DIMENSIONS.Y),

                geom.getCoordinateAt(1, Geometry.DIMENSIONS.X),

                geom.getCoordinateAt(1, Geometry.DIMENSIONS.Y)

        );

        l[1] = manager.distance(

                geom.getCoordinateAt(1, Geometry.DIMENSIONS.X),

                geom.getCoordinateAt(1, Geometry.DIMENSIONS.Y),

                geom.getCoordinateAt(2, Geometry.DIMENSIONS.X),

                geom.getCoordinateAt(2, Geometry.DIMENSIONS.Y)

        );

        l[2] = manager.distance(

                geom.getCoordinateAt(2, Geometry.DIMENSIONS.X),

                geom.getCoordinateAt(2, Geometry.DIMENSIONS.Y),

                geom.getCoordinateAt(3, Geometry.DIMENSIONS.X),

                geom.getCoordinateAt(3, Geometry.DIMENSIONS.Y)

        );

        l[3] = manager.distance(

                geom.getCoordinateAt(3, Geometry.DIMENSIONS.X),

                geom.getCoordinateAt(3, Geometry.DIMENSIONS.Y),

                geom.getCoordinateAt(4, Geometry.DIMENSIONS.X),

                geom.getCoordinateAt(4, Geometry.DIMENSIONS.Y)

        );

        // Comprobamos si se cruzan los lados del trapezoide.

        if( !geom.isSimple() ) {

            throw new IllegalArgumentException("Wrong trapezoid, a convex trapezoid is required");

        }

        // Falta comprobar que no es un trapezoide concavo, que no tiene algun

        // angulo interior concavo.

        // Si es concavo probablemente este dando un calculo de longitud incorrecto.

        int max = 0;

        for (int i = 0; i < l.length; i++) {

            if( l[max] < l[i] ) {

                max = i;

            }

        }

        int opposed = max +2;

        if( opposed>3 ) {

            opposed = 1;

        }

        double n = (l[max]+l[opposed]) / 2;

        return n;

    }

//    public static void main(String[] args) {

//        // https://www.juntadeandalucia.es/averroes/centros-tic/21003232/helvia/sitio/upload/apuntes4____trapezoides.pdf

//        

//        new DefaultLibrariesInitializer().fullInitialize();

//        String wktGeom;

//        Polygon geom;

//        double l;

//        

//        // Trapezoide rectangulo

//        wktGeom = "POLYGON ((200 300, 700 300, 700 200, 200 200, 200 300))";

//        try {

//            geom = (Polygon) GeometryUtils.createFrom(wktGeom);

//            l = convexTrapezoidLength(geom);

//            System.err.println("Trapezoide rectangulo [OK]: "+l);

//        } catch(Exception ex) {

//            System.err.println("Trapezoide rectangulo [ER]: "+ex.getMessage());

//        }

//        

//        // No es un trapezoide

//        wktGeom = "POLYGON ((290 120, 440 60, 560 260, 820 320, 870 340, 840 380, 694 345, 410 260, 360 200, 290 120))";

//        try {

//            geom = (Polygon) GeometryUtils.createFrom(wktGeom);

//            l = convexTrapezoidLength(geom);

//            System.err.println("No es un trapezoide [ER]: "+l);

//        } catch(Exception ex) {

//            System.err.println("No es un trapezoide [OK]: "+ex.getMessage());

//        }

//

//        // Trapezoide convexo

//        wktGeom = "POLYGON ((200 300, 700 300, 533.3333333333334 75.55555555555556, 200 200, 200 300))";

//        try {

//            geom = (Polygon) GeometryUtils.createFrom(wktGeom);

//            l = convexTrapezoidLength(geom);

//            System.err.println("Trapezoide convexo [OK]: "+l);

//        } catch(Exception ex) {

//            System.err.println("Trapezoide convexo [ER]: "+ex.getMessage());

//        }

//        

//        // Trapezoide cruzado

//        wktGeom = "POLYGON ((200 300, 700 300, 400 500, 200 200, 200 300))";

//        try {

//            geom = (Polygon) GeometryUtils.createFrom(wktGeom);

//            l = convexTrapezoidLength(geom);

//            System.err.println("Trapezoide cruzado [ER]: "+l);

//        } catch(Exception ex) {

//            System.err.println("Trapezoide cruzado [OK]: "+ex.getMessage());

//        }

//        

//        // Trapezoide concavo

//        wktGeom = "POLYGON ((450 470, 530 220, 390 280, 200 200, 450 470))";

//        try {

//            geom = (Polygon) GeometryUtils.createFrom(wktGeom);

//            l = convexTrapezoidLength(geom);

//            System.err.println("Trapezoide concavo [ER]: "+l);

//        } catch(Exception ex) {

//            System.err.println("Trapezoide concavo [OK]: "+ex.getMessage());

//        }

//    }

}

        super("Spatial", "PointByAngle", Range.between(3, 5));