arcstring.java

GEo 地理操作源代码

/*$************************************************************************************************
 **
 ** $Id: ArcString.java,v 1.6 2004/03/19 04:11:44 desruisseaux Exp $
 **
 ** $Source: /cvsroot/geoapi/src/org/opengis/spatialschema/geometry/geometry/ArcString.java,v $
 **
 ** Copyright (C) 2003 Open GIS Consortium, Inc. All Rights Reserved. http://www.opengis.org/Legal/
 **
 *************************************************************************************************/
package org.opengis.spatialschema.geometry.geometry;

// J2SE direct dependencies
import java.util.List;

// OpenGIS direct dependencies
import org.opengis.spatialschema.geometry.primitive.CurveInterpolation;
import org.opengis.spatialschema.geometry.primitive.CurveSegment;


/**
 * Similar to a {@linkplain LineString line string} except that the interpolation is
 * by circular arcs. Since it requires 3 points to determine a circular arc, the
 * {@linkplain #getControlPoints control points} are treated as a sequence of overlapping
 * sets of 3 {@linkplain Position positions}, the start of each arc, some point between the
 * start and end, and the end of each arc. Since the end of each arc is the start of the next,
 * this {@linkplain Position position} is not repeated in the {@linkplain #getControlPoints
 * control points} sequence.
 *
 * @UML abstract GM_ArcString
 * @author ISO/DIS 19107
 * @author <A HREF="http://www.opengis.org">OpenGIS&reg; consortium</A>
 * @version 2.0
 *
 * @see GeometryFactory#createArcString
 * @see ArcStringByBulge#asArcString
 */
public interface ArcString extends CurveSegment {
    /**
     * Returns the number of circular arcs in the string. Since the interpolation method
     * requires overlapping sets of 3 positions, the number of arcs determines the number
     * of {@linkplain #getControlPoints control points}:
     *
     * <blockquote>
     * <pre>numArc = ({@link #getControlPoints controlPoints}.length - 1)/2</pre>
     * </blockquote>
     *
     * @return The number of circular arcs.
     * @UML operation numArc
     */
    public int getNumArc();

    /**
     * Returns the sequence of points used to control the arcs in this string. The first three
     * {@linkplain Position positions} in the sequence determines the first arc. Any three
     * consecutive {@linkplain Position positions} beginning with an odd offset, determine
     * another arc in the string.
     *
     * @return The control points. The array size is <code>2*{@link #getNumArc numArc}&nbsp;+1</code>.
     * @UML operation controlPoints
     */
    public PointArray getControlPoints();

    /**
     * The interpolation for a <code>ArcString</code> is
     * "{@linkplain CurveInterpolation#CIRCULAR_ARC_3_POINTS circular arc by 3 points}".
     *
     * @return Always {@link CurveInterpolation#CIRCULAR_ARC_3_POINTS}.
     * @UML operation interpolation
     */
    public CurveInterpolation getInterpolation();

    /**
     * Constructs a sequence of arcs that is the geometric equivalent of this arc string.
     *
     * @return The sequence of arcs.
     * @UML operation asGM_Arc
     */
    public List asArcs();
}