private void WriteIFD(MemoryStream stream, Dictionary <ExifTag, ExifProperty> ifd, IFD ifdtype, long tiffoffset, bool preserveMakerNote)
{
BitConverterEx conv = new BitConverterEx(BitConverterEx.SystemByteOrder, ByteOrder);
// Create a queue of fields to write
Queue <ExifProperty> fieldqueue = new Queue <ExifProperty>();
foreach (ExifProperty prop in ifd.Values)
{
if (prop.Tag != ExifTag.MakerNote)
{
fieldqueue.Enqueue(prop);
}
}
// Push the maker note data to the end
if (ifd.ContainsKey(ExifTag.MakerNote))
{
fieldqueue.Enqueue(ifd[ExifTag.MakerNote]);
}
// Offset to start of field data from start of TIFF header
uint dataoffset = (uint)(2 + ifd.Count * 12 + 4 + stream.Position - tiffoffset);
uint currentdataoffset = dataoffset;
long absolutedataoffset = stream.Position + (2 + ifd.Count * 12 + 4);
bool makernotewritten = false;
// Field count
stream.Write(conv.GetBytes((ushort)ifd.Count), 0, 2);
// Fields
while (fieldqueue.Count != 0)
{
ExifProperty field = fieldqueue.Dequeue();
ExifInterOperability interop = field.Interoperability;
uint fillerbytecount = 0;
// Try to preserve the makernote data offset
if (!makernotewritten &&
!makerNoteProcessed &&
makerNoteOffset != 0 &&
ifdtype == IFD.EXIF &&
field.Tag != ExifTag.MakerNote &&
interop.Data.Length > 4 &&
currentdataoffset + interop.Data.Length > makerNoteOffset &&
ifd.ContainsKey(ExifTag.MakerNote))
{
// Delay writing this field until we write makernote data
fieldqueue.Enqueue(field);
continue;
}
else if (field.Tag == ExifTag.MakerNote)
{
makernotewritten = true;
// We may need to write filler bytes to preserve maker note offset
if (preserveMakerNote && !makerNoteProcessed && (makerNoteOffset > currentdataoffset))
{
fillerbytecount = makerNoteOffset - currentdataoffset;
}
else
{
fillerbytecount = 0;
}
}
// Tag
stream.Write(conv.GetBytes(interop.TagID), 0, 2);
// Type
stream.Write(conv.GetBytes(interop.TypeID), 0, 2);
// Count
stream.Write(conv.GetBytes(interop.Count), 0, 4);
// Field data
byte[] data = interop.Data;
if (ByteOrder != BitConverterEx.SystemByteOrder &&
(interop.TypeID == 3 || interop.TypeID == 4 || interop.TypeID == 9 ||
interop.TypeID == 5 || interop.TypeID == 10))
{
int vlen = 4;
if (interop.TypeID == 3)
{
vlen = 2;
}
int n = data.Length / vlen;
for (int i = 0; i < n; i++)
{
Array.Reverse(data, i * vlen, vlen);
}
}
// Fields containing offsets to other IFDs
// Just store their offets, we will write the values later on when we know the lengths of IFDs
if (ifdtype == IFD.Zeroth && interop.TagID == 0x8769)
{
exifIFDFieldOffset = stream.Position;
}
else if (ifdtype == IFD.Zeroth && interop.TagID == 0x8825)
{
gpsIFDFieldOffset = stream.Position;
}
else if (ifdtype == IFD.EXIF && interop.TagID == 0xa005)
{
interopIFDFieldOffset = stream.Position;
}
else if (ifdtype == IFD.First && interop.TagID == 0x201)
{
thumbOffsetLocation = stream.Position;
}
else if (ifdtype == IFD.First && interop.TagID == 0x202)
{
thumbSizeLocation = stream.Position;
}
// Write 4 byte field value or field data
if (data.Length <= 4)
{
stream.Write(data, 0, data.Length);
for (int i = data.Length; i < 4; i++)
{
stream.WriteByte(0);
}
}
else
{
// Pointer to data area relative to TIFF header
stream.Write(conv.GetBytes(currentdataoffset + fillerbytecount), 0, 4);
// Actual data
long currentoffset = stream.Position;
stream.Seek(absolutedataoffset, SeekOrigin.Begin);
// Write filler bytes
for (int i = 0; i < fillerbytecount; i++)
{
stream.WriteByte(0xFF);
}
stream.Write(data, 0, data.Length);
stream.Seek(currentoffset, SeekOrigin.Begin);
// Increment pointers
currentdataoffset += fillerbytecount + (uint)data.Length;
absolutedataoffset += fillerbytecount + data.Length;
}
}
// Offset to 1st IFD
// We will write zeros for now. This will be filled after we write all IFDs
if (ifdtype == IFD.Zeroth)
{
firstIFDFieldOffset = stream.Position;
}
stream.Write(new byte[] { 0, 0, 0, 0 }, 0, 4);
// Seek to end of IFD
stream.Seek(absolutedataoffset, SeekOrigin.Begin);
// Write thumbnail data
if (ifdtype == IFD.First)
{
if (Thumbnail != null)
{
MemoryStream ts = new MemoryStream();
Thumbnail.Save(ts);
ts.Close();
byte[] thumb = ts.ToArray();
thumbOffsetValue = (uint)(stream.Position - tiffoffset);
thumbSizeValue = (uint)thumb.Length;
stream.Write(thumb, 0, thumb.Length);
ts.Dispose();
}
else
{
thumbOffsetValue = 0;
thumbSizeValue = 0;
}
}
}
/// <summary>
/// Replaces the contents of the APP1 section with the Exif properties.
/// </summary>
private bool WriteExifApp1(bool preserveMakerNote)
{
// Zero out IFD field offsets. We will fill those as we write the IFD sections
exifIFDFieldOffset = 0;
gpsIFDFieldOffset = 0;
interopIFDFieldOffset = 0;
firstIFDFieldOffset = 0;
// We also do not know the location of the embedded thumbnail yet
thumbOffsetLocation = 0;
thumbOffsetValue = 0;
thumbSizeLocation = 0;
thumbSizeValue = 0;
// Write thumbnail tags if they are missing, remove otherwise
if (Thumbnail == null)
{
Properties.Remove(ExifTag.ThumbnailJPEGInterchangeFormat);
Properties.Remove(ExifTag.ThumbnailJPEGInterchangeFormatLength);
}
else
{
if (!Properties.ContainsKey(ExifTag.ThumbnailJPEGInterchangeFormat))
{
Properties.Add(new ExifUInt(ExifTag.ThumbnailJPEGInterchangeFormat, 0));
}
if (!Properties.ContainsKey(ExifTag.ThumbnailJPEGInterchangeFormatLength))
{
Properties.Add(new ExifUInt(ExifTag.ThumbnailJPEGInterchangeFormatLength, 0));
}
}
// Which IFD sections do we have?
Dictionary <ExifTag, ExifProperty> ifdzeroth = new Dictionary <ExifTag, ExifProperty>();
Dictionary <ExifTag, ExifProperty> ifdexif = new Dictionary <ExifTag, ExifProperty>();
Dictionary <ExifTag, ExifProperty> ifdgps = new Dictionary <ExifTag, ExifProperty>();
Dictionary <ExifTag, ExifProperty> ifdinterop = new Dictionary <ExifTag, ExifProperty>();
Dictionary <ExifTag, ExifProperty> ifdfirst = new Dictionary <ExifTag, ExifProperty>();
foreach (ExifProperty prop in Properties)
{
switch (prop.IFD)
{
case IFD.Zeroth:
ifdzeroth.Add(prop.Tag, prop);
break;
case IFD.EXIF:
ifdexif.Add(prop.Tag, prop);
break;
case IFD.GPS:
ifdgps.Add(prop.Tag, prop);
break;
case IFD.Interop:
ifdinterop.Add(prop.Tag, prop);
break;
case IFD.First:
ifdfirst.Add(prop.Tag, prop);
break;
}
}
// Add IFD pointers if they are missing
// We will write the pointer values later on
if (ifdexif.Count != 0 && !ifdzeroth.ContainsKey(ExifTag.EXIFIFDPointer))
{
ifdzeroth.Add(ExifTag.EXIFIFDPointer, new ExifUInt(ExifTag.EXIFIFDPointer, 0));
}
if (ifdgps.Count != 0 && !ifdzeroth.ContainsKey(ExifTag.GPSIFDPointer))
{
ifdzeroth.Add(ExifTag.GPSIFDPointer, new ExifUInt(ExifTag.GPSIFDPointer, 0));
}
if (ifdinterop.Count != 0 && !ifdexif.ContainsKey(ExifTag.InteroperabilityIFDPointer))
{
ifdexif.Add(ExifTag.InteroperabilityIFDPointer, new ExifUInt(ExifTag.InteroperabilityIFDPointer, 0));
}
// Remove IFD pointers if IFD sections are missing
if (ifdexif.Count == 0 && ifdzeroth.ContainsKey(ExifTag.EXIFIFDPointer))
{
ifdzeroth.Remove(ExifTag.EXIFIFDPointer);
}
if (ifdgps.Count == 0 && ifdzeroth.ContainsKey(ExifTag.GPSIFDPointer))
{
ifdzeroth.Remove(ExifTag.GPSIFDPointer);
}
if (ifdinterop.Count == 0 && ifdexif.ContainsKey(ExifTag.InteroperabilityIFDPointer))
{
ifdexif.Remove(ExifTag.InteroperabilityIFDPointer);
}
if (ifdzeroth.Count == 0 && ifdgps.Count == 0 && ifdinterop.Count == 0 && ifdfirst.Count == 0 && Thumbnail == null)
{
// Nothing to write
return(false);
}
// We will need these bitconverter to write byte-ordered data
BitConverterEx bceExif = new BitConverterEx(BitConverterEx.SystemByteOrder, ByteOrder);
// Create a memory stream to write the APP1 section to
MemoryStream ms = new MemoryStream();
// Exif identifer
ms.Write(Encoding.ASCII.GetBytes("Exif\0\0"), 0, 6);
// TIFF header
// Byte order
long tiffoffset = ms.Position;
ms.Write((ByteOrder == BitConverterEx.ByteOrder.LittleEndian ? new byte[] { 0x49, 0x49 } : new byte[] { 0x4D, 0x4D }), 0, 2);
// TIFF ID
ms.Write(bceExif.GetBytes((ushort)42), 0, 2);
// Offset to 0th IFD
ms.Write(bceExif.GetBytes((uint)8), 0, 4);
// Write IFDs
WriteIFD(ms, ifdzeroth, IFD.Zeroth, tiffoffset, preserveMakerNote);
uint exififdrelativeoffset = (uint)(ms.Position - tiffoffset);
WriteIFD(ms, ifdexif, IFD.EXIF, tiffoffset, preserveMakerNote);
uint gpsifdrelativeoffset = (uint)(ms.Position - tiffoffset);
WriteIFD(ms, ifdgps, IFD.GPS, tiffoffset, preserveMakerNote);
uint interopifdrelativeoffset = (uint)(ms.Position - tiffoffset);
WriteIFD(ms, ifdinterop, IFD.Interop, tiffoffset, preserveMakerNote);
uint firstifdrelativeoffset = (uint)(ms.Position - tiffoffset);
WriteIFD(ms, ifdfirst, IFD.First, tiffoffset, preserveMakerNote);
// Now that we now the location of IFDs we can go back and write IFD offsets
if (exifIFDFieldOffset != 0)
{
ms.Seek(exifIFDFieldOffset, SeekOrigin.Begin);
ms.Write(bceExif.GetBytes(exififdrelativeoffset), 0, 4);
}
if (gpsIFDFieldOffset != 0)
{
ms.Seek(gpsIFDFieldOffset, SeekOrigin.Begin);
ms.Write(bceExif.GetBytes(gpsifdrelativeoffset), 0, 4);
}
if (interopIFDFieldOffset != 0)
{
ms.Seek(interopIFDFieldOffset, SeekOrigin.Begin);
ms.Write(bceExif.GetBytes(interopifdrelativeoffset), 0, 4);
}
if (firstIFDFieldOffset != 0)
{
ms.Seek(firstIFDFieldOffset, SeekOrigin.Begin);
ms.Write(bceExif.GetBytes(firstifdrelativeoffset), 0, 4);
}
// We can write thumbnail location now
if (thumbOffsetLocation != 0)
{
ms.Seek(thumbOffsetLocation, SeekOrigin.Begin);
ms.Write(bceExif.GetBytes(thumbOffsetValue), 0, 4);
}
if (thumbSizeLocation != 0)
{
ms.Seek(thumbSizeLocation, SeekOrigin.Begin);
ms.Write(bceExif.GetBytes(thumbSizeValue), 0, 4);
}
ms.Close();
// Return APP1 header
exifApp1.Header = ms.ToArray();
return(true);
}
