/// <summary>
/// Reads a COM segment to find the JPEG comment.
/// </summary>
/// <param name="length">
/// The length of the segment that will be read.
/// </param>
private void ReadCOMSegment(int length)
{
if ((ImageTag.TagTypes & TagLib.TagTypes.JpegComment) != 0x00)
{
return;
}
long position = Tell;
JpegCommentTag com_tag;
if (length == 0)
{
com_tag = new JpegCommentTag();
}
else
{
ByteVector data = ReadBlock(length);
int terminator = data.Find("\0", 0);
if (terminator < 0)
{
com_tag = new JpegCommentTag(data.ToString());
}
else
{
com_tag = new JpegCommentTag(data.Mid(0, terminator).ToString());
}
}
ImageTag.AddTag(com_tag);
AddMetadataBlock(position - 4, length + 4);
}
private void ReadAPP13Segment(ushort length)
{
var data = ReadBlock(length);
var iptc_iim_length = IPTC_IIM_IDENTIFIER.Length;
if (length < iptc_iim_length || data.Mid(0, iptc_iim_length) != IPTC_IIM_IDENTIFIER)
{
return;
}
var headerInfoLen = data.Mid(iptc_iim_length, 1).ToUShort();
int lenToSkip;
if (headerInfoLen > 0)
{
lenToSkip = 1 + headerInfoLen + 4;
}
else
{
lenToSkip = 6;
}
data.RemoveRange(0, iptc_iim_length + lenToSkip);
var reader = new IIM.IIMReader(data);
var tag = reader.Process();
if (tag != null)
{
ImageTag.AddTag(tag);
}
}
/// <summary>
/// Reads a Comment Block at the current position. The current position must
/// point to the 3rd byte of the comment block. (The other 2 bytes are usually
/// read before to identify the comment block)
/// </summary>
private void ReadCommentBlock()
{
long position = Tell;
// Comment Extension
//
// 1 Byte Extension Introducer (0x21)
// 1 Byte Comment Label (0xFE)
// N Bytes Comment Data (Sub Blocks)
// 1 Byte Block Terminator (0x00)
//
// Note, the first 2 bytes are still read to identify the Comment Block.
// Therefore, we only need to read the sub blocks and extract the data.
string comment = ReadSubBlocks();
// Only add the tag, if no one is still contained.
if ((TagTypes & TagTypes.GifComment) == 0x00)
{
ImageTag.AddTag(new GifCommentTag(comment));
// 2 bytes where read before
AddMetadataBlock(position - 2, Tell - position + 2);
}
}
private void ReadApplicationExtensionBlock()
{
long position = Tell;
ByteVector data = ReadBlock(12);
if (data.Count != 12)
{
throw new CorruptFileException("");
}
if (data.Mid(1, 8) == XMP_IDENTIFIER && data.Mid(9, 3) == XMP_AUTH_CODE)
{
long data_start = Tell;
long xmp_trailer_start = Find(new byte[] { 0x00 }, data_start) - XMP_MAGIC_TRAILER.Length + 2;
Seek(data_start, SeekOrigin.Begin);
if (xmp_trailer_start <= data_start)
{
throw new CorruptFileException("No End of XMP data found");
}
int data_length = (int)(xmp_trailer_start - data_start);
ByteVector xmp_data = ReadBlock(data_length);
ImageTag.AddTag(new XmpTag(xmp_data.ToString(StringType.UTF8), this));
AddMetadataBlock(position - 2, 14 + data_length + XMP_MAGIC_TRAILER.Length);
Seek(xmp_trailer_start + XMP_MAGIC_TRAILER.Length, SeekOrigin.Begin);
}
else
{
SkipSubBlocks();
}
}
/// <summary>
/// Reads an zTXt Chunk from file. The current position must be set
/// to the start of the Chunk Data. Such a Chunk contains compressed
/// keywords.
/// </summary>
/// <param name="data_length">
/// A <see cref="System.Int32"/> with the length of the Chunk Data.
/// </param>
/// <remarks>
/// The Chunk may also contain compressed Exif data which is written
/// by other tools. But, since the PNG specification does not support
/// Exif data, we ignore it here.
/// </remarks>
private void ReadzTXtChunk(int data_length)
{
long position = Tell;
// zTXt Chunk
//
// N Bytes Keyword
// 1 Byte Null Separator
// 1 Byte Compression Method
// N Bytes Txt
//
// Followed by 4 Bytes CRC data
ByteVector data = ReadChunkData(data_length);
CheckCRC(zTXt_CHUNK_TYPE, data, ReadCRC());
int terminator_index;
string keyword = ReadKeyword(data, 0, out terminator_index);
if (terminator_index + 1 >= data_length)
{
throw new CorruptFileException("Compression Method byte expected");
}
byte compression_method = data [terminator_index + 1];
ByteVector plain_data = Decompress(compression_method, data.Mid(terminator_index + 2));
// ignore unknown compression methods
if (plain_data == null)
{
return;
}
string value = plain_data.ToString();
RawProfile rawProfile = null;
if (keyword.StartsWith("Raw profile type"))
{
rawProfile = ProcessRawProfile(value);
value = rawProfile.ToString();
}
// handle XMP, which has a fixed header
if (keyword == "xmp" || rawProfile != null && string.Compare(rawProfile.Name, "xmp", StringComparison.InvariantCultureIgnoreCase) == 0)
{
ImageTag.AddTag(new XmpTag(string.Join("", rawProfile.Data.ToArray()), this));
}
else
{
PngTag png_tag = GetTag(TagTypes.Png, true) as PngTag;
if (png_tag.GetKeyword(keyword) == null)
{
png_tag.SetKeyword(keyword, value);
}
}
AddMetadataBlock(position - 8, data_length + 8 + 4);
}
/// <summary>
/// Reads the file with a specified read style.
/// </summary>
/// <param name="propertiesStyle">
/// A <see cref="ReadStyle" /> value specifying at what level
/// of accuracy to read the media properties, or <see
/// cref="ReadStyle.None" /> to ignore the properties.
/// </param>
protected void Read(ReadStyle propertiesStyle)
{
Mode = AccessMode.Read;
try
{
uint first_ifd_offset = ReadHeader();
ReadIFD(first_ifd_offset);
// Find XMP data
var xmp_entry = ImageTag.Exif.Structure.GetEntry(0, (ushort)IFDEntryTag.XMP) as ByteVectorIFDEntry;
if (xmp_entry != null)
{
ImageTag.AddTag(new XmpTag(xmp_entry.Data.ToString(), this));
}
if (propertiesStyle == ReadStyle.None)
{
return;
}
properties = ExtractProperties();
}
finally
{
Mode = AccessMode.Closed;
}
}
private void ReadCommentBlock()
{
long position = Tell;
string comment = ReadSubBlocks();
if ((TagTypes & TagTypes.GifComment) == 0x00)
{
ImageTag.AddTag(new GifCommentTag(comment));
AddMetadataBlock(position - 2, Tell - position + 2);
}
}
/// <summary>
/// Reads an APP13 segment to find IPTC-IIM metadata.
/// </summary>
/// <param name="length">
/// The length of the segment that will be read.
/// </param>
/// <remarks>More info and specs for IPTC-IIM:
/// - Guidelines for Handling Image Metadata (http://www.metadataworkinggroup.org/specs/)
/// - IPTC Standard Photo Metadata (July 2010) (http://www.iptc.org/std/photometadata/specification/IPTC-PhotoMetadata-201007_1.pdf)
/// - Extracting IPTC header information from JPEG images (http://www.codeproject.com/KB/graphics/iptc.aspx?fid=2301&df=90&mpp=25&noise=3&prof=False&sort=Position&view=Quick&fr=51#xx0xx)
/// - Reading IPTC APP14 Segment Header Information from JPEG Images (http://www.codeproject.com/KB/graphics/ReadingIPTCAPP14.aspx?q=iptc)
/// </remarks>
private void ReadAPP13Segment(ushort length)
{
// TODO: if both IPTC-IIM and XMP metadata is contained in a file, we should read
// a IPTC-IIM checksum and compare that with the checksum built over the IIM block.
// Depending on the result we should prefer the information from XMP or IIM.
// Right now we always prefer XMP.
var data = ReadBlock(length);
// The APP13 segment consists of:
// - the string "Photoshop 3.0\u0000"
// - followed by "8BIM"
// - and then the section type "\u0004\u0004".
// There might be multiple 8BIM sections with different types, but we're following
// YAGNI for now and only deal with the one we're interested in (and hope that it's
// the first one).
var iptc_iim_length = IPTC_IIM_IDENTIFIER.Length;
if (length < iptc_iim_length || data.Mid(0, iptc_iim_length) != IPTC_IIM_IDENTIFIER)
{
return;
}
// PS6 introduced a new header with variable length text
var headerInfoLen = data.Mid(iptc_iim_length, 1).ToUShort();
int lenToSkip;
if (headerInfoLen > 0)
{
// PS6 header: 1 byte headerinfolen + headerinfo + 2 bytes 00 padding (?) + 2 bytes length
lenToSkip = 1 + headerInfoLen + 4;
}
else
{
//old style: 4 bytes 00 padding (?) + 2 bytes length
lenToSkip = 6;
}
data.RemoveRange(0, iptc_iim_length + lenToSkip);
var reader = new IIM.IIMReader(data);
var tag = reader.Process();
if (tag != null)
{
ImageTag.AddTag(tag);
}
}
private void ReadAPP1Segment(ushort length)
{
long position = Tell;
ByteVector data = null;
int exif_header_length = 14;
if ((ImageTag.TagTypes & TagLib.TagTypes.TiffIFD) == 0x00 && length >= exif_header_length)
{
data = ReadBlock(exif_header_length);
if (data.Count == exif_header_length && data.Mid(0, 6).ToString().Equals(EXIF_IDENTIFIER))
{
bool is_bigendian = data.Mid(6, 2).ToString().Equals("MM");
ushort magic = data.Mid(8, 2).ToUShort(is_bigendian);
if (magic != 42)
{
throw new Exception(String.Format("Invalid TIFF magic: {0}", magic));
}
uint ifd_offset = data.Mid(10, 4).ToUInt(is_bigendian);
var exif = new IFDTag();
var reader = new IFDReader(this, is_bigendian, exif.Structure, position + 6, ifd_offset, (uint)(length - 6));
reader.Read();
ImageTag.AddTag(exif);
AddMetadataBlock(position - 4, length + 4);
return;
}
}
int xmp_header_length = XmpTag.XAP_NS.Length + 1;
if ((ImageTag.TagTypes & TagLib.TagTypes.XMP) == 0x00 && length >= xmp_header_length)
{
if (data == null)
{
data = ReadBlock(xmp_header_length);
}
else
{
data.Add(ReadBlock(xmp_header_length - exif_header_length));
}
if (data.ToString().Equals(XmpTag.XAP_NS + "\0"))
{
ByteVector xmp_data = ReadBlock(length - xmp_header_length);
ImageTag.AddTag(new XmpTag(xmp_data.ToString(), this));
AddMetadataBlock(position - 4, length + 4);
}
}
}
/// <summary>
/// Gets a tag of a specified type from the current instance,
/// optionally creating a new tag if possible.
/// </summary>
/// <param name="type">
/// A <see cref="TagLib.TagTypes" /> value indicating the
/// type of tag to read.
/// </param>
/// <param name="create">
/// A <see cref="bool" /> value specifying whether or not to
/// try and create the tag if one is not found.
/// </param>
/// <returns>
/// A <see cref="Tag" /> object containing the tag that was
/// found in or added to the current instance. If no
/// matching tag was found and none was created, <see
/// langword="null" /> is returned.
/// </returns>
public override Tag GetTag (TagTypes type, bool create)
{
Tag tag = base.GetTag (type, false);
if (tag != null) {
return tag;
}
if (!create || (type & ImageTag.AllowedTypes) == 0)
return null;
if (type != TagTypes.TiffIFD)
return base.GetTag (type, create);
ImageTag new_tag = new IFDTag (this);
ImageTag.AddTag (new_tag);
return new_tag;
}
/// <summary>
/// Reads an APP13 segment to find IPTC-IIM metadata.
/// </summary>
/// <param name="length">
/// The length of the segment that will be read.
/// </param>
/// <remarks>More info and specs for IPTC-IIM:
/// - Guidelines for Handling Image Metadata (http://www.metadataworkinggroup.org/specs/)
/// - IPTC Standard Photo Metadata (July 2010) (http://www.iptc.org/std/photometadata/specification/IPTC-PhotoMetadata-201007_1.pdf)
/// - Extracting IPTC header information from JPEG images (http://www.codeproject.com/KB/graphics/iptc.aspx?fid=2301&df=90&mpp=25&noise=3&prof=False&sort=Position&view=Quick&fr=51#xx0xx)
/// - Reading IPTC APP14 Segment Header Information from JPEG Images (http://www.codeproject.com/KB/graphics/ReadingIPTCAPP14.aspx?q=iptc)
/// </remarks>
void ReadAPP13Segment(ushort length)
{
var data = ReadBlock(length);
// The APP13 segment consists of:
// - the string "Photoshop 3.0\u0000"
// - followed by "8BIM"
// - and then the section type "\u0004\u0004".
// There might be multiple 8BIM sections with different types, but we're following
// YAGNI for now and only deal with the one we're interested in (and hope that it's
// the first one).
var iptc_iim_length = IPTC_IIM_IDENTIFIER.Length;
if (length < iptc_iim_length || data.Mid(0, iptc_iim_length) != IPTC_IIM_IDENTIFIER)
{
return;
}
// PS6 introduced a new header with variable length text
var headerInfoLen = data.Mid(iptc_iim_length, 1).ToUShort();
int lenToSkip;
if (headerInfoLen > 0)
{
// PS6 header: 1 byte headerinfolen + headerinfo + 2 bytes 00 padding (?) + 2 bytes length
lenToSkip = 1 + headerInfoLen + 4;
}
else
{
//old style: 4 bytes 00 padding (?) + 2 bytes length
lenToSkip = 6;
}
data.RemoveRange(0, iptc_iim_length + lenToSkip);
var reader = new IIM.IIMReader(data);
var tag = reader.Process();
if (tag != null)
{
ImageTag.AddTag(tag);
}
}
private void ReadiTXtChunk(int data_length)
{
long position = Tell;
ByteVector data = ReadChunkData(data_length);
CheckCRC(iTXt_CHUNK_TYPE, data, ReadCRC());
if (data.StartsWith(XMP_CHUNK_HEADER))
{
ImageTag.AddTag(new XmpTag(data.Mid(XMP_CHUNK_HEADER.Length).ToString(StringType.UTF8), this));
AddMetadataBlock(position - 8, data_length + 8 + 4);
return;
}
int terminator_index;
string keyword = ReadKeyword(data, 0, out terminator_index);
if (terminator_index + 2 >= data_length)
{
throw new CorruptFileException("Compression Flag and Compression Method byte expected");
}
byte compression_flag = data[terminator_index + 1];
byte compression_method = data[terminator_index + 2];
ByteVector txt_data = data.Mid(terminator_index + 1);
if (compression_flag != 0x00)
{
txt_data = Decompress(compression_method, txt_data);
if (txt_data == null)
{
return;
}
}
string value = txt_data.ToString();
PngTag png_tag = GetTag(TagTypes.Png, true)
as PngTag;
if (png_tag.GetKeyword(keyword) == null)
{
png_tag.SetKeyword(keyword, value);
}
AddMetadataBlock(position - 8, data_length + 8 + 4);
}
/// <summary>
/// Reads an iTXt Chunk from file. The current position must be set
/// to the start of the Chunk Data. Such a Chunk may contain XMP data
/// or translated keywords.
/// </summary>
/// <param name="data_length">
/// A <see cref="System.Int32"/> with the length of the Chunk Data.
/// </param>
void ReadiTXtChunk(int data_length)
{
long position = Tell;
// iTXt Chunk
//
// N Bytes Keyword
// 1 Byte Null Separator
// 1 Byte Compression Flag (0 for uncompressed data)
// 1 Byte Compression Method
// N Bytes Language Tag
// 1 Byte Null Separator
// N Bytes Translated Keyword
// 1 Byte Null Terminator
// N Bytes Txt
//
// Followed by 4 Bytes CRC data
ByteVector data = ReadChunkData(data_length);
CheckCRC(iTXt_CHUNK_TYPE, data, ReadCRC());
// handle XMP, which has a fixed header
if (data.StartsWith(XMP_CHUNK_HEADER))
{
ImageTag.AddTag(new XmpTag(data.Mid(XMP_CHUNK_HEADER.Length).ToString(StringType.UTF8), this));
AddMetadataBlock(position - 8, data_length + 8 + 4);
return;
}
string keyword = ReadKeyword(data, 0, out var terminator_index);
if (terminator_index + 2 >= data_length)
{
throw new CorruptFileException("Compression Flag and Compression Method byte expected");
}
byte compression_flag = data[terminator_index + 1];
byte compression_method = data[terminator_index + 2];
//string language = ReadTerminatedString (data, terminator_index + 3, out terminator_index);
//string translated_keyword = ReadTerminatedString (data, terminator_index + 1, out terminator_index);
ByteVector txt_data = data.Mid(terminator_index + 1);
if (compression_flag != 0x00)
{
txt_data = Decompress(compression_method, txt_data);
// ignore unknown compression methods
if (txt_data == null)
{
return;
}
}
string value = txt_data.ToString();
var png_tag = GetTag(TagTypes.Png, true) as PngTag;
if (png_tag.GetKeyword(keyword) == null)
{
png_tag.SetKeyword(keyword, value);
}
AddMetadataBlock(position - 8, data_length + 8 + 4);
}
/// <summary>
/// Reads an APP1 segment to find EXIF or XMP metadata.
/// </summary>
/// <param name="length">
/// The length of the segment that will be read.
/// </param>
private void ReadAPP1Segment(ushort length)
{
long position = Tell;
ByteVector data = null;
// for an Exif segment, the data block consists of 14 bytes of:
// * 6 bytes Exif identifier string
// * 2 bytes bigendian indication MM (or II)
// * 2 bytes Tiff magic number (42)
// * 4 bytes offset of the first IFD in this segment
//
// the last two points are alreay encoded according to
// big- or littleendian
int exif_header_length = 14;
// could be an Exif segment
if ((ImageTag.TagTypes & TagLib.TagTypes.TiffIFD) == 0x00 && length >= exif_header_length)
{
data = ReadBlock(exif_header_length);
if (data.Count == exif_header_length &&
data.Mid(0, 6).ToString().Equals(EXIF_IDENTIFIER))
{
bool is_bigendian = data.Mid(6, 2).ToString().Equals("MM");
ushort magic = data.Mid(8, 2).ToUShort(is_bigendian);
if (magic != 42)
{
throw new Exception(String.Format("Invalid TIFF magic: {0}", magic));
}
uint ifd_offset = data.Mid(10, 4).ToUInt(is_bigendian);
var exif = new IFDTag();
var reader = new IFDReader(this, is_bigendian, exif.Structure, position + 6, ifd_offset, (uint)(length - 6));
reader.Read();
ImageTag.AddTag(exif);
AddMetadataBlock(position - 4, length + 4);
return;
}
}
int xmp_header_length = XmpTag.XAP_NS.Length + 1;
// could be an Xmp segment
if ((ImageTag.TagTypes & TagLib.TagTypes.XMP) == 0x00 && length >= xmp_header_length)
{
// if already data is read for determining the Exif segment,
// just read the remaining bytes.
// NOTE: that (exif_header_length < xmp_header_length) holds
if (data == null)
{
data = ReadBlock(xmp_header_length);
}
else
{
data.Add(ReadBlock(xmp_header_length - exif_header_length));
}
if (data.ToString().Equals(XmpTag.XAP_NS + "\0"))
{
ByteVector xmp_data = ReadBlock(length - xmp_header_length);
ImageTag.AddTag(new XmpTag(xmp_data.ToString(), this));
AddMetadataBlock(position - 4, length + 4);
}
}
}
/// <summary>
/// Reads an Application Extension Block at the current position. The current
/// position must point to the 3rd byte of the comment block. (The other 2 bytes
/// are usually read before to identify the comment block)
/// </summary>
private void ReadApplicationExtensionBlock()
{
// Application Extension Block
//
// 1 Byte Extension Introducer (0x21)
// 1 Byte Application Extension Label (0xFF)
// 1 Byte Block Size (0x0B - 11)
// 8 Bytes Application Identifier
// 3 Bytes Application Auth. Code
// N Bytes Application Data (sub blocks)
// 1 Byte Block Terminator (0x00)
//
// Note, the first 2 bytes are still read to identify the Comment Block.
// Therefore, we only need to read the sub blocks and extract the data.
long position = Tell;
ByteVector data = ReadBlock(12);
if (data.Count != 12)
{
throw new CorruptFileException("");
}
// Contains XMP data
if (data.Mid(1, 8) == XMP_IDENTIFIER &&
data.Mid(9, 3) == XMP_AUTH_CODE)
{
// XMP Data is not organized in sub-blocks
// start of xmp data
long data_start = Tell;
// start of trailer start
// FIXME: Since File.Find is still buggy, the following call does not work to find the end of the
// XMP data. Therfore, we use here a different way for now.
//long xmp_trailer_start = Find (new ByteVector (0x00), data_start);
// Since searching just one byte is save, we search for the end of the xmp trailer which
// consists of two 0x00 bytes and compute the expected start.
long xmp_trailer_start = Find(new byte [] { 0x00 }, data_start) - XMP_MAGIC_TRAILER.Length + 2;
Seek(data_start, SeekOrigin.Begin);
if (xmp_trailer_start <= data_start)
{
throw new CorruptFileException("No End of XMP data found");
}
// length of xmp data
int data_length = (int)(xmp_trailer_start - data_start);
ByteVector xmp_data = ReadBlock(data_length);
ImageTag.AddTag(new XmpTag(xmp_data.ToString(StringType.UTF8), this));
// 2 bytes where read before
AddMetadataBlock(position - 2, 14 + data_length + XMP_MAGIC_TRAILER.Length);
// set position behind the XMP block
Seek(xmp_trailer_start + XMP_MAGIC_TRAILER.Length, SeekOrigin.Begin);
}
else
{
SkipSubBlocks();
}
}
