// Utilities
/**
* Returns the number of image directories (subimages) stored in a
* given TIFF file, represented by a <code>SeekableStream</code>.
*/
public static int GetNumDirectories(RandomAccessFileOrArray stream)
{
long pointer = stream.FilePointer; // Save stream pointer
stream.Seek(0L);
int endian = stream.ReadUnsignedShort();
if (!IsValidEndianTag(endian)) {
throw new ArgumentException("Bad endianness tag (not 0x4949 or 0x4d4d).");
}
bool isBigEndian = (endian == 0x4d4d);
int magic = ReadUnsignedShort(stream, isBigEndian);
if (magic != 42) {
throw new
ArgumentException("Bad magic number, should be 42.");
}
stream.Seek(4L);
long offset = ReadUnsignedInt(stream, isBigEndian);
int numDirectories = 0;
while (offset != 0L) {
++numDirectories;
// EOFException means IFD was probably not properly terminated.
try {
stream.Seek(offset);
int entries = ReadUnsignedShort(stream, isBigEndian);
stream.Skip(12*entries);
offset = ReadUnsignedInt(stream, isBigEndian);
} catch (EndOfStreamException) {
//numDirectories--;
break;
}
}
stream.Seek(pointer); // Reset stream pointer
return numDirectories;
}
/**
* Constructs a TIFFDirectory from a SeekableStream.
* The directory parameter specifies which directory to read from
* the linked list present in the stream; directory 0 is normally
* read but it is possible to store multiple images in a single
* TIFF file by maintaing multiple directories.
*
* @param stream a SeekableStream to read from.
* @param directory the index of the directory to read.
*/
public TIFFDirectory(RandomAccessFileOrArray stream, int directory)
{
long global_save_offset = stream.FilePointer;
long ifd_offset;
// Read the TIFF header
stream.Seek(0L);
int endian = stream.ReadUnsignedShort();
if (!IsValidEndianTag(endian)) {
throw new
ArgumentException("Bad endianness tag (not 0x4949 or 0x4d4d).");
}
isBigEndian = (endian == 0x4d4d);
int magic = ReadUnsignedShort(stream);
if (magic != 42) {
throw new
ArgumentException("Bad magic number, should be 42.");
}
// Get the initial ifd offset as an unsigned int (using a long)
ifd_offset = ReadUnsignedInt(stream);
for (int i = 0; i < directory; i++) {
if (ifd_offset == 0L) {
throw new
ArgumentException("Directory number too large.");
}
stream.Seek(ifd_offset);
int entries = ReadUnsignedShort(stream);
stream.Skip(12*entries);
ifd_offset = ReadUnsignedInt(stream);
}
stream.Seek(ifd_offset);
Initialize(stream);
stream.Seek(global_save_offset);
}