cylindrical.java

openmap java写的开源数字地图程序. 用applet实现,可以像google map 那样放大缩小地图.

// **********************************************************************
// 
// <copyright>
// 
//  BBN Technologies
//  10 Moulton Street
//  Cambridge, MA 02138
//  [phone]
// 
//  Copyright (C) BBNT Solutions LLC. All rights reserved.
// 
// </copyright>
// **********************************************************************
// 
// $Source: /cvs/distapps/openmap/src/openmap/com/bbn/openmap/proj/Cylindrical.java,v $
// $RCSfile: Cylindrical.java,v $
// $Revision: 1.5.2.2 $
// $Date: 2005/08/09 21:17:54 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.proj;

import java.awt.*;
import java.util.ArrayList;
import com.bbn.openmap.LatLonPoint;
import com.bbn.openmap.MoreMath;
import com.bbn.openmap.util.Debug;

/**
 * Base of all cylindrical projections.
 * <p>
 * 
 * @see Projection
 * @see Proj
 * @see Mercator
 * @see CADRG
 *  
 */
public abstract class Cylindrical extends Proj {

    // used for calculating wrapping of ArrayList graphics
    protected Point world; // world width in pixels.
    protected int half_world; // world.x / 2

    /**
     * Construct a cylindrical projection.
     * <p>
     * 
     * @param center LatLonPoint center of projection
     * @param scale float scale of projection
     * @param width width of screen
     * @param height height of screen
     * @param type projection type
     *  
     */
    public Cylindrical(LatLonPoint center, float scale, int width, int height,
            int type) {
        super(center, scale, width, height, type);
    }

    /**
     * Return stringified description of this projection.
     * <p>
     * 
     * @return String
     * @see Projection#getProjectionID
     */
    public String toString() {
        return " world(" + world.x + "," + world.y + ")" + super.toString();
    }

    /**
     * Called when some fundamental parameters change.
     * <p>
     * Each projection will decide how to respond to this change. For
     * instance, they may need to recalculate "constant" parameters
     * used in the forward() and inverse() calls.
     * <p>
     */
    protected void computeParameters() {
        planetPixelRadius = planetRadius * pixelsPerMeter;
        planetPixelCircumference = MoreMath.TWO_PI * planetPixelRadius;

        // minscale is the minimum scale allowable (before integer
        // wrapping
        // can occur)
        minscale = (float) Math.ceil(planetPixelCircumference
                / (int) Integer.MAX_VALUE);
        if (minscale < 1)
            minscale = 1;
        if (scale < minscale)
            scale = minscale;

        // maxscale = scale at which world circumference fits in
        // window
        maxscale = (float) planetPixelCircumference / (float) width;
        if (maxscale < minscale) {
            maxscale = minscale;
        }
        if (scale > maxscale) {
            scale = maxscale;
        }
        scaled_radius = planetPixelRadius / scale;

        if (world == null)
            world = new Point(0, 0);

        // width of the world in pixels at current scale
        world.x = (int) (planetPixelCircumference / scale);
        half_world = world.x / 2;

        // calculate cutoff scale for XWindows workaround
        XSCALE_THRESHOLD = (int) (planetPixelCircumference / 64000);//fudge
                                                                    // it a
                                                                    // little
                                                                    // bit

        if (Debug.debugging("proj")) {
            Debug.output("Cylindrical.computeParameters(): " + "world.x = "
                    + world.x + " half_world = " + half_world
                    + " XSCALE_THRESHOLD = " + XSCALE_THRESHOLD);
        }
    }

    /**
     * Pan the map/projection.
     * <ul>
     * <li><code>pan(