/**
* Returns the number of image directories (subimages) stored in a given TIFF file, represented by
* a <code>SeekableStream</code>.
*/
public static int getNumDirectories(SeekableStream stream) throws IOException {
long pointer = stream.getFilePointer(); // Save stream pointer
stream.seek(0L);
int endian = stream.readUnsignedShort();
if (!isValidEndianTag(endian)) {
throw new IllegalArgumentException("TIFFDirectory1");
}
boolean isBigEndian = (endian == 0x4d4d);
int magic = readUnsignedShort(stream, isBigEndian);
if (magic != 42) {
throw new IllegalArgumentException("TIFFDirectory2");
}
stream.seek(4L);
long offset = readUnsignedInt(stream, isBigEndian);
int numDirectories = 0;
while (offset != 0L) {
++numDirectories;
stream.seek(offset);
long entries = readUnsignedShort(stream, isBigEndian);
stream.skipFully(12 * entries);
offset = readUnsignedInt(stream, isBigEndian);
}
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(SeekableStream stream, int directory) throws IOException {
long global_save_offset = stream.getFilePointer();
long ifd_offset;
// Read the TIFF header
stream.seek(0L);
int endian = stream.readUnsignedShort();
if (!isValidEndianTag(endian)) {
throw new IllegalArgumentException("TIFFDirectory1");
}
isBigEndian = (endian == 0x4d4d);
int magic = readUnsignedShort(stream);
if (magic != 42) {
throw new IllegalArgumentException("TIFFDirectory2");
}
// 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 IllegalArgumentException("TIFFDirectory3");
}
stream.seek(ifd_offset);
long entries = readUnsignedShort(stream);
stream.skipFully(12 * entries);
ifd_offset = readUnsignedInt(stream);
}
stream.seek(ifd_offset);
initialize(stream);
stream.seek(global_save_offset);
}
