poi/src/scratchpad/src/org/apache/poi/hslf/blip/PNG.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.poi.hslf.blip;

import org.apache.poi.hslf.model.Picture;
import org.apache.poi.util.PngUtils;

/**
 * Represents a PNG picture data in a PPT file
 *
 * @author Yegor Kozlov
 */
public final class PNG extends Bitmap {

    /**
     * @return PNG data
     */
    public byte[] getData() {
        byte[] data = super.getData();

        //PNG created on MAC may have a 16-byte prefix which prevents successful reading.
        //Just cut it off!.
        if (PngUtils.matchesPngHeader(data, 16)) {
            byte[] png = new byte[data.length-16];
            System.arraycopy(data, 16, png, 0, png.length);
            data = png;
        }

        return data;
    }

    /**
     * @return type of  this picture
     * @see  org.apache.poi.hslf.model.Picture#PNG
     */
    public int getType(){
        return Picture.PNG;
    }

    /**
     * PNG signature is {@code 0x6E00} or {@code 0x6E10}
     *
     * @return PNG signature ({@code 0x6E00} or {@code 0x6E10})
     */
    public int getSignature(){
        return (uidInstanceCount == 1 ? 0x6E00 : 0x6E10);
    }
    
    /**
     * Sets the PNG signature - either {@code 0x6E00} or {@code 0x6E10}
     */
    public void setSignature(int signature) {
        switch (signature) {
            case 0x6E00:
                uidInstanceCount = 1;
                break;
            case 0x6E10:
                uidInstanceCount = 2;
                break;
            default:
                throw new IllegalArgumentException(signature+" is not a valid instance/signature value for PNG");
        }        
    }
}