/// <summary>
/// Computes the size of the image file directory.
/// </summary>
/// <param name="imageFileDirectory">The image file directory.</param>
/// <returns>The size of the image file directory (in bytes).</returns>
private Int64 ComputeImageFileDirectorySize(TiffImageFileDirectory imageFileDirectory)
{
Int64 size = (_structure == TiffStructure.BigTiff ? 8 : 2) // number of entries
+ _imageFileDirectoryEntrySize * imageFileDirectory.Count // entries
+ _imageFileDirectoryFieldSize; // position of next directory
TiffTagType entryType;
UInt16 dataSize;
Int32 dataCount;
foreach (UInt16 entryTag in imageFileDirectory.Keys)
{
entryType = TiffTag.GetType(imageFileDirectory[entryTag][0]);
dataSize = TiffTag.GetSize(entryType);
if (entryType == TiffTagType.ASCII)
{
dataCount = 0;
for (Int32 i = 0; i < imageFileDirectory[entryTag].Length; i++)
{
dataCount += (imageFileDirectory[entryTag][i] as String).Length;
}
}
else
{
dataCount = imageFileDirectory[entryTag].Length;
}
if (dataCount * dataSize > _imageFileDirectoryFieldSize)
{
size += dataCount * dataSize + (dataCount * dataSize) % 2;
}
}
return(size);
}
/// <summary>
/// Writes an image file directory to the stream.
/// </summary>
/// <param name="imageFileDirectory">The image file directory.</param>
private void WriteImageFileDirectory(TiffImageFileDirectory imageFileDirectory)
{
_currentImageFileDirectoryStartPosition = _baseStream.Position;
// write starting position
_baseStream.Seek(_currentImageFileDirectoryEndPosition, SeekOrigin.Begin);
_baseStream.Write(EndianBitConverter.GetBytes((UInt32)_currentImageFileDirectoryStartPosition), 0, _imageFileDirectoryFieldSize);
// compute size of directory (without additional fields)
Int64 imageFileDirectorySize = 2 + _imageFileDirectoryEntrySize * imageFileDirectory.Count;
_currentImageFileDirectoryEndPosition = _currentImageFileDirectoryStartPosition + imageFileDirectorySize;
// position after the IFD to write exceeding values
_baseStream.Seek(_currentImageFileDirectoryEndPosition + _imageFileDirectoryFieldSize, SeekOrigin.Begin);
// the IFD should be written in one operation
Byte[] bytes;
if (_imageCount == _maxImageCount - 1)
{
bytes = new Byte[imageFileDirectorySize + _imageFileDirectoryFieldSize];
}
else
{
bytes = new Byte[imageFileDirectorySize];
}
EndianBitConverter.CopyBytes((UInt16)imageFileDirectory.Count, bytes, 0); // number of entries
Int32 byteIndex = 2;
TiffTagType entryType;
UInt16 dataSize;
Int64 dataCount;
foreach (UInt16 entryTag in imageFileDirectory.Keys)
{
entryType = TiffTag.GetType(imageFileDirectory[entryTag][0]);
dataSize = TiffTag.GetSize(entryType);
if (entryType == TiffTagType.ASCII)
{
dataCount = 0;
for (Int32 i = 0; i < imageFileDirectory[entryTag].Length; i++)
{
dataCount += (imageFileDirectory[entryTag][i] as String).Length;
}
}
else
{
dataCount = imageFileDirectory[entryTag].Length;
}
EndianBitConverter.CopyBytes(entryTag, bytes, byteIndex);
EndianBitConverter.CopyBytes((UInt16)entryType, bytes, byteIndex + 2);
EndianBitConverter.CopyBytes((UInt32)dataCount, bytes, byteIndex + 4);
// values exceeding he field size (4) must be written to another position
Byte[] dataBytes;
Int32 dataStartIndex;
if (dataCount * dataSize <= 4)
{
dataBytes = bytes;
dataStartIndex = byteIndex + 8;
}
else
{
dataBytes = new Byte[dataCount * dataSize + (dataCount * dataSize) % 2];
dataStartIndex = 0;
}
for (Int32 valueIndex = 0; valueIndex < imageFileDirectory[entryTag].Length; valueIndex++)
{
dataStartIndex = TiffTag.SetValue(entryType, imageFileDirectory[entryTag][valueIndex], dataBytes, dataStartIndex);
}
if (dataCount * dataSize > 4)
{
Int64 valuePosition = _baseStream.Position;
_baseStream.Write(dataBytes, 0, dataBytes.Length);
EndianBitConverter.CopyBytes((UInt32)valuePosition, bytes, byteIndex + 8);
}
byteIndex += _imageFileDirectoryEntrySize;
}
_currentImageStartPosition = _baseStream.Position;
// write the IFD
_baseStream.Seek(_currentImageFileDirectoryStartPosition, SeekOrigin.Begin);
_baseStream.Write(bytes, 0, bytes.Length);
}
