fop/src/java/org/apache/fop/render/extensions/prepress/PageScale.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

/* $Id$ */

package org.apache.fop.render.extensions.prepress;

import java.awt.geom.Point2D;
import java.text.MessageFormat;
import java.util.regex.Pattern;

import org.apache.xmlgraphics.util.QName;

import org.apache.fop.fo.extensions.ExtensionElementMapping;

/**
 * This class provides utility methods to parse the 'fox:scale' extension attribute.
 */
public final class PageScale {

    /**
     * The extension 'scale' attribute for the simple-page-master element.
     */
    public static final QName EXT_PAGE_SCALE
            = new QName(ExtensionElementMapping.URI, null, "scale");

    private static final Pattern WHITESPACE_PATTERN = Pattern.compile("\\s+");

    /**
     * Utility classes should not have a public or default constructor
     */
    private PageScale() {
    }

    /**
     * Compute scale parameters from given fox:scale attribute which has the format: scaleX [scaleY]
     * If scaleY is not defined, it equals scaleX.
     * @param scale scale attribute, input format: scaleX [scaleY]
     * @return the pair of (sx, sy) values
     */
    public static Point2D getScale(String scale) {
        // TODO throw appropriate exceptions that can be caught by the event
        // notification mechanism
        final String err = "Extension 'scale' attribute has incorrect value(s): {0}";

        if (scale == null || scale.equals("")) {
            return null;
        }

        String[] scales = WHITESPACE_PATTERN.split(scale);
        double scaleX;
        try {
            scaleX = Double.parseDouble(scales[0]);
        } catch (NumberFormatException nfe) {
            throw new IllegalArgumentException(MessageFormat.format(err, new Object[]{scale}));
        }
        double scaleY;
        switch (scales.length) {
        case 1:
            scaleY = scaleX;
            break;
        case 2:
            try {
                scaleY = Double.parseDouble(scales[1]);
            } catch (NumberFormatException nfe) {
                throw new IllegalArgumentException(MessageFormat.format(err, new Object[]{scale}));
            }
            break;
        default:
            throw new IllegalArgumentException("Too many arguments");
        }
        if (scaleX <= 0 || scaleY <= 0) {
            throw new IllegalArgumentException(MessageFormat.format(err, new Object[]{scale}));
        }

        return new Point2D.Double(scaleX, scaleY);
    }
}