/*
* Copyright 2002-2012 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.almalence.util.exifreader.metadata.exif;
import com.almalence.util.exifreader.lang.BufferBoundsException;
import com.almalence.util.exifreader.lang.BufferReader;
import com.almalence.util.exifreader.lang.Rational;
import com.almalence.util.exifreader.lang.annotations.NotNull;
import com.almalence.util.exifreader.metadata.Directory;
import com.almalence.util.exifreader.metadata.Metadata;
import com.almalence.util.exifreader.metadata.MetadataReader;
import java.util.HashSet;
import java.util.Set;
/**
* Decodes Exif binary data, populating a {@link Metadata} object with tag values in {@link ExifSubIFDDirectory},
* {@link ExifThumbnailDirectory}, {@link ExifInteropDirectory}, {@link GpsDirectory} and one of the many camera makernote directories.
*
* @author Drew Noakes http://drewnoakes.com
*/
public class ExifReader implements MetadataReader
{
// extract a reusable TiffReader from this class with hooks for special tag handling and subdir following
/** The number of bytes used per format descriptor. */
@NotNull
private static final int[] BYTES_PER_FORMAT = { 0, 1, 1, 2, 4, 8, 1, 1, 2, 4, 8, 4, 8 };
/** The number of formats known. */
private static final int MAX_FORMAT_CODE = 12;
// Format types
// use an enum for these?
/** An 8-bit unsigned integer. */
private static final int FMT_BYTE = 1;
/** A fixed-length character string. */
private static final int FMT_STRING = 2;
/** An unsigned 16-bit integer. */
private static final int FMT_USHORT = 3;
/** An unsigned 32-bit integer. */
private static final int FMT_ULONG = 4;
private static final int FMT_URATIONAL = 5;
/** An 8-bit signed integer. */
private static final int FMT_SBYTE = 6;
private static final int FMT_UNDEFINED = 7;
/** A signed 16-bit integer. */
private static final int FMT_SSHORT = 8;
/** A signed 32-bit integer. */
private static final int FMT_SLONG = 9;
private static final int FMT_SRATIONAL = 10;
/** A 32-bit floating point number. */
private static final int FMT_SINGLE = 11;
/** A 64-bit floating point number. */
private static final int FMT_DOUBLE = 12;
/** This tag is a pointer to the Exif SubIFD. */
public static final int TAG_EXIF_SUB_IFD_OFFSET = 0x8769;
/** This tag is a pointer to the Exif Interop IFD. */
public static final int TAG_INTEROP_OFFSET = 0xA005;
/** This tag is a pointer to the Exif GPS IFD. */
public static final int TAG_GPS_INFO_OFFSET = 0x8825;
/** This tag is a pointer to the Exif Makernote IFD. */
public static final int TAG_MAKER_NOTE_OFFSET = 0x927C;
public static final int TIFF_HEADER_START_OFFSET = 6;
/**
* Performs the Exif data extraction, adding found values to the specified
* instance of <code>Metadata</code>.
*
* @param reader The buffer reader from which Exif data should be read.
* @param metadata The Metadata object into which extracted values should be merged.
*/
public void extract(@NotNull final BufferReader reader, @NotNull Metadata metadata)
{
final ExifSubIFDDirectory directory = metadata.getOrCreateDirectory(ExifSubIFDDirectory.class);
// check for the header length
if (reader.getLength() <= 14) {
directory.addError("Exif data segment must contain at least 14 bytes");
return;
}
// check for the header preamble
try {
if (!reader.getString(0, 6).equals("Exif\0\0")) {
directory.addError("Exif data segment doesn't begin with 'Exif'");
return;
}
extractIFD(metadata, metadata.getOrCreateDirectory(ExifIFD0Directory.class), TIFF_HEADER_START_OFFSET, reader);
} catch (BufferBoundsException e) {
directory.addError("Exif data segment ended prematurely");
}
}
/**
* Performs the Exif data extraction on a TIFF/RAW, adding found values to the specified
* instance of <code>Metadata</code>.
*
* @param reader The BufferReader from which TIFF data should be read.
* @param metadata The Metadata object into which extracted values should be merged.
*/
public void extractTiff(@NotNull BufferReader reader, @NotNull Metadata metadata)
{
final ExifIFD0Directory directory = metadata.getOrCreateDirectory(ExifIFD0Directory.class);
try {
extractIFD(metadata, directory, 0, reader);
} catch (BufferBoundsException e) {
directory.addError("Exif data segment ended prematurely");
}
}
private void extractIFD(@NotNull Metadata metadata, @NotNull final ExifIFD0Directory directory, int tiffHeaderOffset, @NotNull BufferReader reader) throws BufferBoundsException
{
// this should be either "MM" or "II"
String byteOrderIdentifier = reader.getString(tiffHeaderOffset, 2);
if ("MM".equals(byteOrderIdentifier)) {
reader.setMotorolaByteOrder(true);
} else if ("II".equals(byteOrderIdentifier)) {
reader.setMotorolaByteOrder(false);
} else {
directory.addError("Unclear distinction between Motorola/Intel byte ordering: " + byteOrderIdentifier);
return;
}
// Check the next two values for correctness.
final int tiffMarker = reader.getUInt16(2 + tiffHeaderOffset);
final int standardTiffMarker = 0x002A;
final int olympusRawTiffMarker = 0x4F52; // for ORF files
final int panasonicRawTiffMarker = 0x0055; // for RW2 files
if (tiffMarker != standardTiffMarker && tiffMarker != olympusRawTiffMarker && tiffMarker != panasonicRawTiffMarker) {
directory.addError("Unexpected TIFF marker after byte order identifier: 0x" + Integer.toHexString(tiffMarker));
return;
}
int firstDirectoryOffset = reader.getInt32(4 + tiffHeaderOffset) + tiffHeaderOffset;
// David Ekholm sent a digital camera image that has this problem
if (firstDirectoryOffset >= reader.getLength() - 1) {
directory.addError("First exif directory offset is beyond end of Exif data segment");
// First directory normally starts 14 bytes in -- try it here and catch another error in the worst case
firstDirectoryOffset = 14;
}
Set<Integer> processedDirectoryOffsets = new HashSet<Integer>();
processDirectory(directory, processedDirectoryOffsets, firstDirectoryOffset, tiffHeaderOffset, metadata, reader);
}
/**
* Process one of the nested Tiff IFD directories.
* <p/>
* Header
* 2 bytes: number of tags
* <p/>
* Then for each tag
* 2 bytes: tag type
* 2 bytes: format code
* 4 bytes: component count
*/
private void processDirectory(@NotNull Directory directory, @NotNull Set<Integer> processedDirectoryOffsets, int dirStartOffset, int tiffHeaderOffset, @NotNull final Metadata metadata, @NotNull final BufferReader reader) throws BufferBoundsException
{
// check for directories we've already visited to avoid stack overflows when recursive/cyclic directory structures exist
if (processedDirectoryOffsets.contains(Integer.valueOf(dirStartOffset)))
return;
// remember that we've visited this directory so that we don't visit it again later
processedDirectoryOffsets.add(dirStartOffset);
if (dirStartOffset >= reader.getLength() || dirStartOffset < 0) {
directory.addError("Ignored directory marked to start outside data segment");
return;
}
// First two bytes in the IFD are the number of tags in this directory
int dirTagCount = reader.getUInt16(dirStartOffset);
int dirLength = (2 + (12 * dirTagCount) + 4);
if (dirLength + dirStartOffset > reader.getLength()) {
directory.addError("Illegally sized directory");
return;
}
// Handle each tag in this directory
for (int tagNumber = 0; tagNumber < dirTagCount; tagNumber++) {
final int tagOffset = calculateTagOffset(dirStartOffset, tagNumber);
// 2 bytes for the tag type
final int tagType = reader.getUInt16(tagOffset);
// 2 bytes for the format code
final int formatCode = reader.getUInt16(tagOffset + 2);
if (formatCode < 1 || formatCode > MAX_FORMAT_CODE) {
// This error suggests that we are processing at an incorrect index and will generate
// rubbish until we go out of bounds (which may be a while). Exit now.
directory.addError("Invalid TIFF tag format code: " + formatCode);
return;
}
// 4 bytes dictate the number of components in this tag's data
final int componentCount = reader.getInt32(tagOffset + 4);
if (componentCount < 0) {
directory.addError("Negative TIFF tag component count");
continue;
}
// each component may have more than one byte... calculate the total number of bytes
final int byteCount = componentCount * BYTES_PER_FORMAT[formatCode];
final int tagValueOffset;
if (byteCount > 4) {
// If it's bigger than 4 bytes, the dir entry contains an offset.
// dirEntryOffset must be passed, as some makernote implementations (e.g. FujiFilm) incorrectly use an
// offset relative to the start of the makernote itself, not the TIFF segment.
final int offsetVal = reader.getInt32(tagOffset + 8);
if (offsetVal + byteCount > reader.getLength()) {
// Bogus pointer offset and / or byteCount value
directory.addError("Illegal TIFF tag pointer offset");
continue;
}
tagValueOffset = tiffHeaderOffset + offsetVal;
} else {
// 4 bytes or less and value is in the dir entry itself
tagValueOffset = tagOffset + 8;
}
if (tagValueOffset < 0 || tagValueOffset > reader.getLength()) {
directory.addError("Illegal TIFF tag pointer offset");
continue;
}
// Check that this tag isn't going to allocate outside the bounds of the data array.
// This addresses an uncommon OutOfMemoryError.
if (byteCount < 0 || tagValueOffset + byteCount > reader.getLength()) {
directory.addError("Illegal number of bytes: " + byteCount);
continue;
}
switch (tagType) {
case TAG_EXIF_SUB_IFD_OFFSET: {
final int subdirOffset = tiffHeaderOffset + reader.getInt32(tagValueOffset);
processDirectory(metadata.getOrCreateDirectory(ExifSubIFDDirectory.class), processedDirectoryOffsets, subdirOffset, tiffHeaderOffset, metadata, reader);
continue;
}
case TAG_MAKER_NOTE_OFFSET: {
processMakerNote(tagValueOffset, processedDirectoryOffsets, tiffHeaderOffset, metadata, reader);
continue;
}
default: {
processTag(directory, tagType, tagValueOffset, componentCount, formatCode, reader);
break;
}
}
}
// at the end of each IFD is an optional link to the next IFD
final int finalTagOffset = calculateTagOffset(dirStartOffset, dirTagCount);
int nextDirectoryOffset = reader.getInt32(finalTagOffset);
if (nextDirectoryOffset != 0) {
nextDirectoryOffset += tiffHeaderOffset;
if (nextDirectoryOffset >= reader.getLength()) {
// Last 4 bytes of IFD reference another IFD with an address that is out of bounds
// Note this could have been caused by jhead 1.3 cropping too much
return;
} else if (nextDirectoryOffset < dirStartOffset) {
// Last 4 bytes of IFD reference another IFD with an address that is before the start of this directory
return;
}
}
}
private void processMakerNote(int subdirOffset, @NotNull Set<Integer> processedDirectoryOffsets, int tiffHeaderOffset, @NotNull final Metadata metadata, @NotNull BufferReader reader) throws BufferBoundsException
{
// Determine the camera model and makernote format
Directory ifd0Directory = metadata.getDirectory(ExifIFD0Directory.class);
if (ifd0Directory==null)
return;
}
private void processTag(@NotNull Directory directory, int tagType, int tagValueOffset, int componentCount, int formatCode, @NotNull final BufferReader reader) throws BufferBoundsException
{
// Directory simply stores raw values
// The display side uses a Descriptor class per directory to turn the raw values into 'pretty' descriptions
switch (formatCode) {
case FMT_UNDEFINED:
// this includes exif user comments
directory.setByteArray(tagType, reader.getBytes(tagValueOffset, componentCount));
break;
case FMT_STRING:
String string = reader.getNullTerminatedString(tagValueOffset, componentCount);
directory.setString(tagType, string);
break;
case FMT_SRATIONAL:
if (componentCount == 1) {
directory.setRational(tagType, new Rational(reader.getInt32(tagValueOffset), reader.getInt32(tagValueOffset + 4)));
} else if (componentCount > 1) {
Rational[] rationals = new Rational[componentCount];
for (int i = 0; i < componentCount; i++)
rationals[i] = new Rational(reader.getInt32(tagValueOffset + (8 * i)), reader.getInt32(tagValueOffset + 4 + (8 * i)));
directory.setRationalArray(tagType, rationals);
}
break;
case FMT_URATIONAL:
if (componentCount == 1) {
directory.setRational(tagType, new Rational(reader.getUInt32(tagValueOffset), reader.getUInt32(tagValueOffset + 4)));
} else if (componentCount > 1) {
Rational[] rationals = new Rational[componentCount];
for (int i = 0; i < componentCount; i++)
rationals[i] = new Rational(reader.getUInt32(tagValueOffset + (8 * i)), reader.getUInt32(tagValueOffset + 4 + (8 * i)));
directory.setRationalArray(tagType, rationals);
}
break;
case FMT_SINGLE:
if (componentCount == 1) {
directory.setFloat(tagType, reader.getFloat32(tagValueOffset));
} else {
float[] floats = new float[componentCount];
for (int i = 0; i < componentCount; i++)
floats[i] = reader.getFloat32(tagValueOffset + (i * 4));
directory.setFloatArray(tagType, floats);
}
break;
case FMT_DOUBLE:
if (componentCount == 1) {
directory.setDouble(tagType, reader.getDouble64(tagValueOffset));
} else {
double[] doubles = new double[componentCount];
for (int i = 0; i < componentCount; i++)
doubles[i] = reader.getDouble64(tagValueOffset + (i * 4));
directory.setDoubleArray(tagType, doubles);
}
break;
//
// Note that all integral types are stored as int32 internally (the largest supported by TIFF)
//
case FMT_SBYTE:
if (componentCount == 1) {
directory.setInt(tagType, reader.getInt8(tagValueOffset));
} else {
int[] bytes = new int[componentCount];
for (int i = 0; i < componentCount; i++)
bytes[i] = reader.getInt8(tagValueOffset + i);
directory.setIntArray(tagType, bytes);
}
break;
case FMT_BYTE:
if (componentCount == 1) {
directory.setInt(tagType, reader.getUInt8(tagValueOffset));
} else {
int[] bytes = new int[componentCount];
for (int i = 0; i < componentCount; i++)
bytes[i] = reader.getUInt8(tagValueOffset + i);
directory.setIntArray(tagType, bytes);
}
break;
case FMT_USHORT:
if (componentCount == 1) {
int i = reader.getUInt16(tagValueOffset);
directory.setInt(tagType, i);
} else {
int[] ints = new int[componentCount];
for (int i = 0; i < componentCount; i++)
ints[i] = reader.getUInt16(tagValueOffset + (i * 2));
directory.setIntArray(tagType, ints);
}
break;
case FMT_SSHORT:
if (componentCount == 1) {
int i = reader.getInt16(tagValueOffset);
directory.setInt(tagType, i);
} else {
int[] ints = new int[componentCount];
for (int i = 0; i < componentCount; i++)
ints[i] = reader.getInt16(tagValueOffset + (i * 2));
directory.setIntArray(tagType, ints);
}
break;
case FMT_SLONG:
case FMT_ULONG:
// NOTE 'long' in this case means 32 bit, not 64
if (componentCount == 1) {
int i = reader.getInt32(tagValueOffset);
directory.setInt(tagType, i);
} else {
int[] ints = new int[componentCount];
for (int i = 0; i < componentCount; i++)
ints[i] = reader.getInt32(tagValueOffset + (i * 4));
directory.setIntArray(tagType, ints);
}
break;
default:
directory.addError("Unknown format code " + formatCode + " for tag " + tagType);
}
}
/**
* Determine the offset at which a given InteropArray entry begins within the specified IFD.
*
* @param dirStartOffset the offset at which the IFD starts
* @param entryNumber the zero-based entry number
*/
private int calculateTagOffset(int dirStartOffset, int entryNumber)
{
// add 2 bytes for the tag count
// each entry is 12 bytes, so we skip 12 * the number seen so far
return dirStartOffset + 2 + (12 * entryNumber);
}
}