001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.imaging.formats.png.transparencyfilters;
018
019import static org.apache.commons.imaging.common.BinaryFunctions.read2Bytes;
020
021import java.io.ByteArrayInputStream;
022import java.io.IOException;
023
024import org.apache.commons.imaging.ImagingException;
025
026public final class TransparencyFilterGrayscale extends AbstractTransparencyFilter {
027    private final int transparentColor;
028
029    public TransparencyFilterGrayscale(final byte[] bytes) throws IOException {
030        super(bytes);
031
032        final ByteArrayInputStream is = new ByteArrayInputStream(bytes);
033        transparentColor = read2Bytes("transparentColor", is, "tRNS: Missing transparentColor", getByteOrder());
034    }
035
036    @Override
037    public int filter(final int rgb, final int index) throws ImagingException, IOException {
038        if (index != transparentColor) {
039            return rgb;
040        }
041        return 0x00;
042    }
043}