/*
* Copyright 2002-2013 Drew Noakes
*
* 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
*
* 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.
*
* More information about this project is available at:
*
* http://drewnoakes.com/code/exif/
* http://code.google.com/p/metadata-extractor/
*/
package com.drew.metadata.jpeg;
import com.drew.imaging.jpeg.JpegSegmentMetadataReader;
import com.drew.imaging.jpeg.JpegSegmentType;
import com.drew.lang.SequentialByteArrayReader;
import com.drew.lang.SequentialReader;
import com.drew.lang.annotations.NotNull;
import com.drew.metadata.Metadata;
import java.io.IOException;
import java.util.Arrays;
/**
* Decodes JPEG SOFn data, populating a {@link Metadata} object with tag values in a {@link JpegDirectory}.
*
* @author Drew Noakes http://drewnoakes.com
* @author Darrell Silver http://www.darrellsilver.com
*/
public class JpegReader implements JpegSegmentMetadataReader
{
@NotNull
public Iterable<JpegSegmentType> getSegmentTypes()
{
// NOTE that some SOFn values do not exist
return Arrays.asList(
JpegSegmentType.SOF0,
JpegSegmentType.SOF1,
JpegSegmentType.SOF2,
JpegSegmentType.SOF3,
// JpegSegmentType.SOF4,
JpegSegmentType.SOF5,
JpegSegmentType.SOF6,
JpegSegmentType.SOF7,
JpegSegmentType.SOF8,
JpegSegmentType.SOF9,
JpegSegmentType.SOF10,
JpegSegmentType.SOF11,
// JpegSegmentType.SOF12,
JpegSegmentType.SOF13,
JpegSegmentType.SOF14,
JpegSegmentType.SOF15
);
}
public boolean canProcess(@NotNull byte[] segmentBytes, @NotNull JpegSegmentType segmentType)
{
return true;
}
public void extract(@NotNull byte[] segmentBytes, @NotNull Metadata metadata, @NotNull JpegSegmentType segmentType)
{
if (metadata.containsDirectory(JpegDirectory.class)) {
// If this directory is already present, discontinue this operation.
// We only store metadata for the *first* matching SOFn segment.
return;
}
JpegDirectory directory = metadata.getOrCreateDirectory(JpegDirectory.class);
// The value of TAG_COMPRESSION_TYPE is determined by the segment type found
directory.setInt(JpegDirectory.TAG_COMPRESSION_TYPE, segmentType.byteValue - JpegSegmentType.SOF0.byteValue);
SequentialReader reader = new SequentialByteArrayReader(segmentBytes);
try {
directory.setInt(JpegDirectory.TAG_DATA_PRECISION, reader.getUInt8());
directory.setInt(JpegDirectory.TAG_IMAGE_HEIGHT, reader.getUInt16());
directory.setInt(JpegDirectory.TAG_IMAGE_WIDTH, reader.getUInt16());
short componentCount = reader.getUInt8();
directory.setInt(JpegDirectory.TAG_NUMBER_OF_COMPONENTS, componentCount);
// for each component, there are three bytes of data:
// 1 - Component ID: 1 = Y, 2 = Cb, 3 = Cr, 4 = I, 5 = Q
// 2 - Sampling factors: bit 0-3 vertical, 4-7 horizontal
// 3 - Quantization table number
for (int i = 0; i < (int)componentCount; i++) {
final int componentId = reader.getUInt8();
final int samplingFactorByte = reader.getUInt8();
final int quantizationTableNumber = reader.getUInt8();
final JpegComponent component = new JpegComponent(componentId, samplingFactorByte, quantizationTableNumber);
directory.setObject(JpegDirectory.TAG_COMPONENT_DATA_1 + i, component);
}
} catch (IOException ex) {
directory.addError(ex.getMessage());
}
}
}