org.geomajas.gwt.client.widget.ScaleConverter.java Source code

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Here is the source code for org.geomajas.gwt.client.widget.ScaleConverter.java

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/*
 * This is part of Geomajas, a GIS framework, http://www.geomajas.org/.
 *
 * Copyright 2008-2013 Geosparc nv, http://www.geosparc.com/, Belgium.
 *
 * The program is available in open source according to the GNU Affero
 * General Public License. All contributions in this program are covered
 * by the Geomajas Contributors License Agreement. For full licensing
 * details, see LICENSE.txt in the project root.
 */

package org.geomajas.gwt.client.widget;

import com.google.gwt.i18n.client.NumberFormat;

/**
 * Utility class for converting scales to string and the reverse.
 *
 * @author Joachim Van der Auwera
 */
public final class ScaleConverter {

    public static final String ERROR_SCALE = "Negative or zero scale not allowed, did you use a correct pixel length?";

    private ScaleConverter() {
        // do not allow instantiation
    }

    /**
     * Convert a scale to a string representation.
     *
     * @param scale scale to convert
     * @param precision precision for the scale, or 0
     * @param significantDigits maximum number of significant digits
     * @return string representation for the scale
     */
    public static String scaleToString(double scale, int precision, int significantDigits) {
        NumberFormat numberFormat = NumberFormat.getFormat("###,###");
        if (scale > 0 && scale < 1.0) {
            int denominator = round((int) Math.round(1.0 / scale), precision, significantDigits);
            return "1 : " + numberFormat.format(denominator);
        } else if (scale >= 1.0) {
            int nominator = round((int) Math.round(scale), precision, significantDigits);
            return numberFormat.format(nominator) + " : 1";
        } else {
            return ERROR_SCALE;
        }
    }

    /**
     * Parse scale from string representation.
     *
     * @param value to parse
     * @return scale value
     */
    public static Double stringToScale(String value) {
        NumberFormat numberFormat = NumberFormat.getFormat("###,###");
        String[] scale2 = value.split(":");
        if (scale2.length == 1) {
            return 1.0 / numberFormat.parse(scale2[0].trim());
        } else {
            return numberFormat.parse(scale2[0].trim()) / numberFormat.parse(scale2[1].trim());
        }
    }

    /**
     * Round integer number by applying precision and maximum significant digits.
     *
     * @param value value to round
     * @param precision precision
     * @param significantDigits significant digits
     * @return rounded value
     */
    static int round(int value, int precision, int significantDigits) {
        if (precision > 0) {
            value = (value + precision / 2) / precision * precision;
        }
        if (significantDigits > 0) {
            int forRounding = value;
            int precisionMax = (int) Math.pow(10, significantDigits);
            int multiplier = 1;
            while (value > precisionMax) {
                forRounding = value;
                multiplier *= 10;
                value /= 10;
            }
            if (forRounding % 10 >= 5) {
                value++;
            }
            value *= multiplier;
        }
        return value;
    }
}