batik-bridge/src/main/java/org/apache/batik/bridge/SVGMaskElementBridge.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.

 */
package org.apache.batik.bridge;

import java.awt.geom.AffineTransform;
import java.awt.geom.Rectangle2D;

import org.apache.batik.ext.awt.image.renderable.Filter;
import org.apache.batik.gvt.CompositeGraphicsNode;
import org.apache.batik.gvt.GraphicsNode;
import org.apache.batik.gvt.filter.Mask;
import org.apache.batik.gvt.filter.MaskRable8Bit;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

/**
 * Bridge class for the <mask> element.
 *
 * @author <a href="mailto:tkormann@apache.org">Thierry Kormann</a>
 * @version $Id$
 */
public class SVGMaskElementBridge extends AnimatableGenericSVGBridge
        implements MaskBridge {

    /**
     * Constructs a new bridge for the &lt;mask&gt; element.
     */
    public SVGMaskElementBridge() {}

    /**
     * Returns 'mask'.
     */
    public String getLocalName() {
        return SVG_MASK_TAG;
    }

    /**
     * Creates a <code>Mask</code> according to the specified parameters.
     *
     * @param ctx the bridge context to use
     * @param maskElement the element that defines the mask
     * @param maskedElement the element that references the mask element
     * @param maskedNode the graphics node to mask
     */
    public Mask createMask(BridgeContext ctx,
                           Element maskElement,
                           Element maskedElement,
                           GraphicsNode maskedNode) {

        String s;

        // get mask region using 'maskUnits'
        Rectangle2D maskRegion = SVGUtilities.convertMaskRegion
            (maskElement, maskedElement, maskedNode, ctx);

        //
        // Build the GVT tree that represents the mask
        //
        GVTBuilder builder = ctx.getGVTBuilder();
        CompositeGraphicsNode maskNode = new CompositeGraphicsNode();
        CompositeGraphicsNode maskNodeContent = new CompositeGraphicsNode();
        maskNode.getChildren().add(maskNodeContent);
        boolean hasChildren = false;
        for(Node node = maskElement.getFirstChild();
            node != null;
            node = node.getNextSibling()){

            // check if the node is a valid Element
            if(node.getNodeType() != Node.ELEMENT_NODE) {
                continue;
            }

            Element child = (Element)node;
            GraphicsNode gn = builder.build(ctx, child) ;
            if(gn == null) {
                continue;
            }
            hasChildren = true;
            maskNodeContent.getChildren().add(gn);
        }
        if (!hasChildren) {
            return null; // empty mask
        }

        // 'transform' attribute
        AffineTransform Tx;
        s = maskElement.getAttributeNS(null, SVG_TRANSFORM_ATTRIBUTE);
        if (s.length() != 0) {
            Tx = SVGUtilities.convertTransform
                (maskElement, SVG_TRANSFORM_ATTRIBUTE, s, ctx);
        } else {
            Tx = new AffineTransform();
        }

        // 'maskContentUnits' attribute - default is userSpaceOnUse
        short coordSystemType;
        s = maskElement.getAttributeNS(null, SVG_MASK_CONTENT_UNITS_ATTRIBUTE);
        if (s.length() == 0) {
            coordSystemType = SVGUtilities.USER_SPACE_ON_USE;
        } else {
            coordSystemType = SVGUtilities.parseCoordinateSystem
                (maskElement, SVG_MASK_CONTENT_UNITS_ATTRIBUTE, s, ctx);
        }

        // additional transform to move to objectBoundingBox coordinate system
        if (coordSystemType == SVGUtilities.OBJECT_BOUNDING_BOX) {
            Tx = SVGUtilities.toObjectBBox(Tx, maskedNode);
        }

        maskNodeContent.setTransform(Tx);

        Filter filter = maskedNode.getFilter();
        if (filter == null) {
            // Make the initial source as a RenderableImage
            filter = maskedNode.getGraphicsNodeRable(true);
        }

        return new MaskRable8Bit(filter, maskNode, maskRegion);
    }
}