/// <summary>
/// Try to parse the given IFD entry, used to discover format-specific entries.
/// </summary>
/// <param name="tag">
/// A <see cref="System.UInt16"/> with the tag of the entry.
/// </param>
/// <param name="type">
/// A <see cref="System.UInt16"/> with the type of the entry.
/// </param>
/// <param name="count">
/// A <see cref="System.UInt32"/> with the data count of the entry.
/// </param>
/// <param name="base_offset">
/// A <see cref="System.Int64"/> with the base offset which every offsets in the
/// IFD are relative to.
/// </param>
/// <param name="offset">
/// A <see cref="System.UInt32"/> with the offset of the entry.
/// </param>
/// <returns>
/// A <see cref="IFDEntry"/> with the given parameters, or null if none was parsed, after
/// which the normal TIFF parsing is used.
/// </returns>
protected override IFDEntry ParseIFDEntry(ushort tag, ushort type, uint count, long base_offset, uint offset)
{
if (tag == (ushort)Nikon3MakerNoteEntryTag.Preview)
{
// SubIFD with Preview Image
// The entry itself is usually a long
// 2TODO: handle JPEGInterchangeFormat and JPEGInterchangeFormatLength correctly
// The preview field contains a long with an offset to an IFD
// that contains the preview image. We need to be careful
// though: this IFD does not contain a valid next-offset
// pointer. For this reason, we only read the first IFD and
// ignore the rest (which is preview image data, directly
// starting after the IFD entries).
type = (ushort)IFDEntryType.IFD;
IFDStructure ifd_structure = new IFDStructure();
IFDReader reader = CreateSubIFDReader(file, is_bigendian, ifd_structure, base_offset, offset, max_offset);
reader.Read(1);
return(new SubIFDEntry(tag, type, (uint)ifd_structure.Directories.Length, ifd_structure));
}
return(base.ParseIFDEntry(tag, type, count, base_offset, offset));
}
protected override IFDEntry ParseIFDEntry(ushort tag, ushort type, uint count, long base_offset, uint offset)
{
if (tag == (ushort)Nikon3MakerNoteEntryTag.Preview)
{
type = (ushort)IFDEntryType.IFD;
IFDStructure ifd_structure = new IFDStructure();
IFDReader reader = CreateSubIFDReader(file, is_bigendian, ifd_structure, base_offset, offset, max_offset);
reader.Read(1);
return(new SubIFDEntry(tag, type, (uint)ifd_structure.Directories.Length, ifd_structure));
}
return(base.ParseIFDEntry(tag, type, count, base_offset, offset));
}
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>
/// 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);
}
}
}