content: /*
   * Copyright 2002-2019 Drew Noakes and contributors
   *
   *    Licensed 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
   *
   *        https://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.
   *
   * More information about this project is available at:
   *
   *    https://drewnoakes.com/code/exif/
   *    https://github.com/drewnoakes/metadata-extractor
   */
  package com.drew.metadata.jfif;
  
  import com.drew.imaging.jpeg.JpegSegmentMetadataReader;
  import com.drew.imaging.jpeg.JpegSegmentType;
  import com.drew.lang.ByteArrayReader;
  import com.drew.lang.RandomAccessReader;
  import com.drew.lang.annotations.NotNull;
  import com.drew.metadata.Metadata;
  import com.drew.metadata.MetadataReader;
  
  import java.io.IOException;
  import java.util.Collections;
  
  /**
   * Reader for JFIF data, found in the APP0 JPEG segment.
   *
   * <ul>
   *   <li>https://en.wikipedia.org/wiki/JPEG_File_Interchange_Format</li>
   *   <li>https://www.w3.org/Graphics/JPEG/jfif3.pdf</li>
   * </ul>
   *
   * @author Yuri Binev, Drew Noakes, Markus Meyer
   */
  public class JfifReader implements JpegSegmentMetadataReader, MetadataReader
  {
      public static final String PREAMBLE = "JFIF";
  
      @NotNull
      public Iterable<JpegSegmentType> getSegmentTypes()
      {
          return Collections.singletonList(JpegSegmentType.APP0);
      }
  
      public void readJpegSegments(@NotNull Iterable<byte[]> segments, @NotNull Metadata metadata, @NotNull JpegSegmentType segmentType)
      {
          for (byte[] segmentBytes : segments) {
              // Skip segments not starting with the required header
              if (segmentBytes.length >= PREAMBLE.length() && PREAMBLE.equals(new String(segmentBytes, 0, PREAMBLE.length())))
                  extract(new ByteArrayReader(segmentBytes), metadata);
          }
      }
  
      /**
       * Performs the Jfif data extraction, adding found values to the specified
       * instance of {@link Metadata}.
       */
      public void extract(@NotNull final RandomAccessReader reader, @NotNull final Metadata metadata)
      {
          JfifDirectory directory = new JfifDirectory();
          metadata.addDirectory(directory);
  
          try {
              // For JFIF, the tag number is also the offset into the segment
  
              directory.setInt(JfifDirectory.TAG_VERSION,      reader.getUInt16(JfifDirectory.TAG_VERSION));
              directory.setInt(JfifDirectory.TAG_UNITS,        reader.getUInt8(JfifDirectory.TAG_UNITS));
              directory.setInt(JfifDirectory.TAG_RESX,         reader.getUInt16(JfifDirectory.TAG_RESX));
              directory.setInt(JfifDirectory.TAG_RESY,         reader.getUInt16(JfifDirectory.TAG_RESY));
              directory.setInt(JfifDirectory.TAG_THUMB_WIDTH,  reader.getUInt8(JfifDirectory.TAG_THUMB_WIDTH));
              directory.setInt(JfifDirectory.TAG_THUMB_HEIGHT, reader.getUInt8(JfifDirectory.TAG_THUMB_HEIGHT));
          } catch (IOException me) {
              directory.addError(me.getMessage());
          }
      }
  }
  