private static void ProcessIFD(Com.Drew.Metadata.Directory directory, ICollection<int> processedIfdOffsets, int ifdOffset, int tiffHeaderOffset, Com.Drew.Metadata.Metadata metadata, RandomAccessReader reader)
{
// check for directories we've already visited to avoid stack overflows when recursive/cyclic directory structures exist
if (processedIfdOffsets.Contains(Sharpen.Extensions.ValueOf(ifdOffset)))
{
return;
}
// remember that we've visited this directory so that we don't visit it again later
processedIfdOffsets.Add(ifdOffset);
if (ifdOffset >= reader.GetLength() || ifdOffset < 0)
{
directory.AddError("Ignored IFD 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(ifdOffset);
int dirLength = (2 + (12 * dirTagCount) + 4);
if (dirLength + ifdOffset > reader.GetLength())
{
directory.AddError("Illegally sized IFD");
return;
}
// Handle each tag in this directory
for (int tagNumber = 0; tagNumber < dirTagCount; tagNumber++)
{
int tagOffset = CalculateTagOffset(ifdOffset, tagNumber);
// 2 bytes for the tag type
int tagType = reader.GetUInt16(tagOffset);
// 2 bytes for the format code
int formatCode = reader.GetUInt16(tagOffset + 2);
if (formatCode < 1 || formatCode > MaxFormatCode)
{
// 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
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
int byteCount = componentCount * BytesPerFormat[formatCode];
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.
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 for TIFF tag data: " + byteCount);
continue;
}
//
// Special handling for certain known tags that point to or contain other chunks of data to be processed
//
if (tagType == ExifIFD0Directory.TagExifSubIfdOffset && directory is ExifIFD0Directory)
{
if (byteCount != 4)
{
directory.AddError("Exif SubIFD Offset tag should have a component count of four (bytes) for the offset.");
}
else
{
int subDirOffset = tiffHeaderOffset + reader.GetInt32(tagValueOffset);
ProcessIFD(metadata.GetOrCreateDirectory<ExifSubIFDDirectory>(), processedIfdOffsets, subDirOffset, tiffHeaderOffset, metadata, reader);
}
}
else
{
if (tagType == ExifSubIFDDirectory.TagInteropOffset && directory is ExifSubIFDDirectory)
{
if (byteCount != 4)
{
directory.AddError("Exif Interop Offset tag should have a component count of four (bytes) for the offset.");
}
else
{
int subDirOffset = tiffHeaderOffset + reader.GetInt32(tagValueOffset);
ProcessIFD(metadata.GetOrCreateDirectory<ExifInteropDirectory>(), processedIfdOffsets, subDirOffset, tiffHeaderOffset, metadata, reader);
}
}
else
{
if (tagType == ExifIFD0Directory.TagGpsInfoOffset && directory is ExifIFD0Directory)
{
if (byteCount != 4)
{
directory.AddError("Exif GPS Info Offset tag should have a component count of four (bytes) for the offset.");
}
else
{
int subDirOffset = tiffHeaderOffset + reader.GetInt32(tagValueOffset);
ProcessIFD(metadata.GetOrCreateDirectory<GpsDirectory>(), processedIfdOffsets, subDirOffset, tiffHeaderOffset, metadata, reader);
}
}
else
{
if (tagType == ExifSubIFDDirectory.TagMakernote && directory is ExifSubIFDDirectory)
{
// The makernote tag contains the encoded makernote data directly.
// Pass the offset to this tag's value. Manufacturer/Model-specific logic will be used to
// determine the correct offset for further processing.
ProcessMakernote(tagValueOffset, processedIfdOffsets, tiffHeaderOffset, metadata, reader);
}
else
{
ProcessTag(directory, tagType, tagValueOffset, componentCount, formatCode, reader);
}
}
}
}
}
// at the end of each IFD is an optional link to the next IFD
int finalTagOffset = CalculateTagOffset(ifdOffset, 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 < ifdOffset)
{
// Last 4 bytes of IFD reference another IFD with an address that is before the start of this directory
return;
}
}
// TODO in Exif, the only known 'follower' IFD is the thumbnail one, however this may not be the case
ExifThumbnailDirectory nextDirectory = metadata.GetOrCreateDirectory<ExifThumbnailDirectory>();
ProcessIFD(nextDirectory, processedIfdOffsets, nextDirectoryOffset, tiffHeaderOffset, metadata, reader);
}
}
private static void ProcessTag(Com.Drew.Metadata.Directory directory, int tagType, int tagValueOffset, int componentCount, int formatCode, RandomAccessReader reader)
{
switch (formatCode)
{
case FmtUndefined:
{
// Directory simply stores raw values
// The display side uses a Descriptor class per directory to turn the raw values into 'pretty' descriptions
// this includes exif user comments
directory.SetByteArray(tagType, reader.GetBytes(tagValueOffset, componentCount));
break;
}
case FmtString:
{
string @string = reader.GetNullTerminatedString(tagValueOffset, componentCount);
directory.SetString(tagType, @string);
break;
}
case FmtSrational:
{
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 FmtUrational:
{
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 FmtSingle:
{
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 FmtDouble:
{
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;
}
case FmtSbyte:
{
//
// Note that all integral types are stored as int32 internally (the largest supported by TIFF)
//
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 FmtByte:
{
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 FmtUshort:
{
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 FmtSshort:
{
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 FmtSlong:
case FmtUlong:
{
// 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);
break;
}
}
}
private static void ExtractTiff(RandomAccessReader reader, Com.Drew.Metadata.Metadata metadata, Com.Drew.Metadata.Directory firstDirectory, int tiffHeaderOffset)
{
// 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
{
firstDirectory.AddError("Unclear distinction between Motorola/Intel byte ordering: " + byteOrderIdentifier);
return;
}
}
// Check the next two values for correctness.
int tiffMarker = reader.GetUInt16(2 + tiffHeaderOffset);
int standardTiffMarker = unchecked((int)(0x002A));
int olympusRawTiffMarker = unchecked((int)(0x4F52));
// for ORF files
int panasonicRawTiffMarker = unchecked((int)(0x0055));
// for RW2 files
if (tiffMarker != standardTiffMarker && tiffMarker != olympusRawTiffMarker && tiffMarker != panasonicRawTiffMarker)
{
firstDirectory.AddError("Unexpected TIFF marker after byte order identifier: 0x" + Sharpen.Extensions.ToHexString(tiffMarker));
return;
}
int firstIfdOffset = reader.GetInt32(4 + tiffHeaderOffset) + tiffHeaderOffset;
// David Ekholm sent a digital camera image that has this problem
// TODO getLength should be avoided as it causes RandomAccessStreamReader to read to the end of the stream
if (firstIfdOffset >= reader.GetLength() - 1)
{
firstDirectory.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
firstIfdOffset = 14;
}
ICollection<int> processedIfdOffsets = new HashSet<int>();
ProcessIFD(firstDirectory, processedIfdOffsets, firstIfdOffset, tiffHeaderOffset, metadata, reader);
// after the extraction process, if we have the correct tags, we may be able to store thumbnail information
ExifThumbnailDirectory thumbnailDirectory = metadata.GetDirectory<ExifThumbnailDirectory>();
if (thumbnailDirectory != null && thumbnailDirectory.ContainsTag(ExifThumbnailDirectory.TagThumbnailCompression))
{
int? offset = thumbnailDirectory.GetInteger(ExifThumbnailDirectory.TagThumbnailOffset);
int? length = thumbnailDirectory.GetInteger(ExifThumbnailDirectory.TagThumbnailLength);
if (offset != null && length != null)
{
try
{
sbyte[] thumbnailData = reader.GetBytes(tiffHeaderOffset + offset.Value, length.Value);
thumbnailDirectory.SetThumbnailData(thumbnailData);
}
catch (IOException ex)
{
firstDirectory.AddError("Invalid thumbnail data specification: " + ex.Message);
}
}
}
}