/**
* Check if data is valid TIFF data.
*
* This will read just enough data from the data window to determine
* if the data could be a valid TIFF data. This means that the
* check is more like a heuristic than a rigorous check.
*
* @param PelDataWindow $d
* the bytes that will be examined.
*
* @return boolean true if the data looks like valid TIFF data,
* false otherwise.
*
* @see PelJpeg::isValid()
*/
public static function isValid(PelDataWindow $d)
{
/* First check that we have enough data. */
if ($d->getSize() < 8) {
return false;
}
/* Byte order */
if ($d->strcmp(0, 'II')) {
$d->setByteOrder(PelConvert::LITTLE_ENDIAN);
} elseif ($d->strcmp(0, 'MM')) {
Pel::debug('Found Motorola byte order');
$d->setByteOrder(PelConvert::BIG_ENDIAN);
} else {
return false;
}
/* Verify the TIFF header */
return $d->getShort(2) == self::TIFF_HEADER;
}
/**
* Load and parse Exif data.
*
* This will populate the object with Exif data, contained as a
* {@link PelTiff} object. This TIFF object can be accessed with
* the {@link getTiff()} method.
*
* @param PelDataWindow $d
*/
public function load(PelDataWindow $d)
{
Pel::debug('Parsing %d bytes of Exif data...', $d->getSize());
/* There must be at least 6 bytes for the Exif header. */
if ($d->getSize() < 6) {
throw new PelInvalidDataException('Expected at least 6 bytes of Exif ' . 'data, found just %d bytes.', $d->getSize());
}
/* Verify the Exif header */
if ($d->strcmp(0, self::EXIF_HEADER)) {
$d->setWindowStart(strlen(self::EXIF_HEADER));
} else {
throw new PelInvalidDataException('Exif header not found.');
}
/* The rest of the data is TIFF data. */
$this->tiff = new PelTiff();
$this->tiff->load($d);
}
