FoucautSinusoidalProjection.java

/*
Copyright 2006 Jerry Huxtable

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.
 */

/*
 * This file was semi-automatically converted from the public-domain USGS PROJ source.
 *
 */

/**
 * Modified by Bernhard Jenny: added setter for parameter n,
 * added missing initialization of n to 0.5, as is done by proj4,
 * added missing isEqualArea, change superclass from Projection to
 * PseudocylindricalProjection.
 */

package com.jhlabs.map.proj;

import com.jhlabs.map.MapMath;
import java.awt.geom.*;

public class FoucautSinusoidalProjection extends PseudoCylindricalProjection {

    private double n = 0.5;
    private double n1;
    private final static int MAX_ITER = 10;
    private final static double LOOP_TOL = 1e-7;

    public Point2D.Double project(double lplam, double lpphi, Point2D.Double out) {
        double t;

        t = Math.cos(lpphi);
        out.x = lplam * t / (n + n1 * t);
        out.y = n * lpphi + n1 * Math.sin(lpphi);
        return out;
    }

    public Point2D.Double projectInverse(double xyx, double xyy, Point2D.Double out) {
        double V;
        int i;

        if (n != 0) {
            out.y = xyy;
            for (i = MAX_ITER; i > 0; --i) {
                out.y -= V = (n * out.y + n1 * Math.sin(out.y) - xyy)
                        / (n + n1 * Math.cos(out.y));
                if (Math.abs(V) < LOOP_TOL) {
                    break;
                }
            }
            if (i == 0) {
                out.y = xyy < 0. ? -MapMath.HALFPI : MapMath.HALFPI;
            }
        } else {
            out.y = MapMath.asin(xyy);
        }
        V = Math.cos(out.y);
        out.x = xyx * (n + n1 * V) / V;
        return out;
    }

    public void initialize() {
        super.initialize();
//		n = pj_param(params, "dn").f;
        if (n < 0. || n > 1.) {
            throw new ProjectionException("-99");
        }
        n1 = 1. - n;
    }

    public boolean hasInverse() {
        return true;
    }

    public boolean isEqualArea() {
        return true;
    }

    public String toString() {
        return "Foucaut Sinusoidal";
    }

    public double getN() {
        return n;
    }

    public void setN(double n) {
        if (n < 0 || n > 1) {
            throw new IllegalArgumentException();
        }
        this.n = n;
        this.n1 = 1d - n;
    }
}