/*
    * 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.commons.imaging.formats.png.transparencyfilters;
  
  import static org.apache.commons.imaging.common.BinaryFunctions.read2Bytes;
  
  import java.io.ByteArrayInputStream;
  import java.io.IOException;
  
  import org.apache.commons.imaging.ImagingException;
  
  public class TransparencyFilterGrayscale extends AbstractTransparencyFilter {
      private final int transparentColor;
  
      public TransparencyFilterGrayscale(final byte[] bytes) throws IOException {
          super(bytes);
  
          final ByteArrayInputStream is = new ByteArrayInputStream(bytes);
          transparentColor = read2Bytes("transparentColor", is, "tRNS: Missing transparentColor", getByteOrder());
      }
  
      @Override
      public int filter(final int rgb, final int index) throws ImagingException, IOException {
          if (index != transparentColor) {
              return rgb;
          }
          return 0x00;
      }
  }