sources/org/apache/batik/ext/awt/image/rendered/FilterAlphaRed.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.ext.awt.image.rendered;

import java.awt.image.Raster;
import java.awt.image.SampleModel;
import java.awt.image.WritableRaster;

import org.apache.batik.ext.awt.ColorSpaceHintKey;

/**
 * This strips out the source alpha channel into a one band image.
 *
 * @author <a href="mailto:Thomas.DeWeeese@Kodak.com">Thomas DeWeese</a>
 * @version $Id$ */
public class FilterAlphaRed extends AbstractRed {

    /**
     * Construct an alpah channel from the given src, according to
     * the SVG masking rules.
     *
     * @param src The image to convert to an alpha channel (mask image)
     */
    public FilterAlphaRed(CachableRed src) {
        super(src, src.getBounds(), 
              src.getColorModel(),
              src.getSampleModel(),
              src.getTileGridXOffset(),
              src.getTileGridYOffset(),
              null);

        props.put(ColorSpaceHintKey.PROPERTY_COLORSPACE,
                  ColorSpaceHintKey.VALUE_COLORSPACE_ALPHA);
    }

    public WritableRaster copyData(WritableRaster wr) {
        // new Exception("FilterAlphaRed: ").printStackTrace();
        // Get my source.
        CachableRed srcRed = (CachableRed)getSources().get(0);

        SampleModel sm = srcRed.getSampleModel();
        if (sm.getNumBands() == 1)
            // Already one band of data so we just use it...
            return srcRed.copyData(wr);

        PadRed.ZeroRecter.zeroRect(wr);
        Raster srcRas = srcRed.getData(wr.getBounds());
        AbstractRed.copyBand(srcRas, srcRas.getNumBands()-1, wr, 
                             wr.getNumBands()-1);
        return wr;
    }

}